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Technical Illustrations for college textbook on the Physics of High Fidelity.

Technical Illustrations for college textbook on the Physics of High Fidelity.

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  • 1. Contents 1 Introduction to Hi-Fi 1 2 Waves 14 3 Decibels 63 4 Loudspeakers 67 5 Electricity 112 6 Ampli
  • 2. ers 138 7 Electromagnetism 153 8 Electromagnetic Waves and Tuners 173 9 Analog Recording and Playback 202 10 Digital Optical Recording & Playback 226 11 Digital Magnetic Recording & Playback 247 12 Heat 260 13 Mechanics 273 i
  • 3. List of Figures 1.1 Stereo process in recording and playback. : : : : : : : : : : : 2 1.2 Surround sound reproduction of audio information. : : : : : : 3 1.3 Storage or transmission of sound in stereo. : : : : : : : : : : : 3 1.4 Playback process in stereo. : : : : : : : : : : : : : : : : : : : 4 1.5 Elements of a receiver. : : : : : : : : : : : : : : : : : : : : : : 4 1.6 Example of basic connections to a receiver. : : : : : : : : : : 5 1.7 Elements of an integrated ampli
  • 4. er. : : : : : : : : : : : : : : 5 1.8 Connections to an integrated ampli
  • 5. er. : : : : : : : : : : : : : 6 1.9 All separate approach. : : : : : : : : : : : : : : : : : : : : : : 6 1.10 Connections in all-separate approach. : : : : : : : : : : : : : 7 1.11 Basic A/V System. : : : : : : : : : : : : : : : : : : : : : : : : 8 1.12 A/V receiver driving a surround-sound system. : : : : : : : : 9 1.13 Details of the tape monitor switch when listening to a sound source with available tape recording. : : : : : : : : : : : : : : 10 1.14 Listening to a tape; tape switch in. : : : : : : : : : : : : : : : 11 1.15 A/V receiver with Dolby Pro Logic processor. : : : : : : : : : 12 1.16 Various wave forms. : : : : : : : : : : : : : : : : : : : : : : : 13 2.1 Phono record and an enlarged groove showing engraved wave representing sound. : : : : : : : : : : : : : : : : : : : : : : : : 15 2.2 Simpli
  • 6. ed picture of a water wave; displaced water as a func- tion of position. : : : : : : : : : : : : : : : : : : : : : : : : : : 15 2.3 Details of one wave as a function of position. : : : : : : : : : 16 2.4 Large and small amplitude waves. : : : : : : : : : : : : : : : : 16 2.5 Time dependence of displacement of a point on a water wave. 17 2.6 Displacement as a function of time; time required to complete one wave. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 17 2.7 Transverse wave on a string. : : : : : : : : : : : : : : : : : : : 18 2.8 Longitudinal waves along a solid bar. : : : : : : : : : : : : : : 18 ii
  • 7. 2.9 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 18 2.10 Sound requires a medium in which to propagate; in a vacuum there is no sound propagation. : : : : : : : : : : : : : : : : : 19 2.11 Direct radiator speaker can move air like a drumhead. : : : : 19 2.12 Generation of sound by loudspeaker. : : : : : : : : : : : : : : 20 2.13 Disturbances created by loudspeaker; pressure changes cause sound. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 21 2.14 Representation of sound created by a loudspeaker. : : : : : : 21 2.15 Wave Y has 4 times the power of wave X, but their ampli- tudes di er only by a factor of 2. : : : : : : : : : : : : : : : : 22 2.16 Re ection of a wave by an obstacle or a di erent medium. : : 22 2.17 Speaker producing a pulse of sound in a hall. : : : : : : : : : 23 2.18 Paths of direct and re ected sound in a hall. : : : : : : : : : : 24 2.19 Direct and reverberant sound in a hall. : : : : : : : : : : : : : 25 2.20 Direct and reverberant sound contributions to sound in a hall. 26 2.21 Sound radiated by a speaker; as one moves away the intensity decreases. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 27 2.22 Sound intensity through surface 2 is di erent from that of 1. : 28 2.23 Observer and source at rest and in relative motion. : : : : : : 29 2.24 Doppler E ect produced by speaker producing simultane- ously 100 Hz and 1,000 Hz sound waves. : : : : : : : : : : : : 30 2.25 Sound wave in cold air entering hot air. : : : : : : : : : : : : 31 2.26 Refraction of a sound wave. : : : : : : : : : : : : : : : : : : : 31 2.27 Above a critical angle of incidence there is only re ection. : : 32 2.28 Sound travels in a curved hollow plastic tube by multiple re ections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 33 2.29 Sound wave produced by a musical group; a complex wave. : 34 2.30 Simple sine waveform. : : : : : : : : : : : : : : : : : : : : : : 34 2.31 Comparison between one full wave and one rotation of a circle. 35 2.32 Addition of two waves. : : : : : : : : : : : : : : : : : : : : : : 35 2.33 Addition of two waves out of phase by 180 degrees. : : : : : : 35 2.34 Constructive interference. : : : : : : : : : : : : : : : : : : : : 36 2.35 Destructive interference. : : : : : : : : : : : : : : : : : : : : : 37 2.36 Obstacle with aperture receiving high frequency waves. : : : : 38 2.37 Low frequency behavior of obstacle and aperture. : : : : : : : 39 2.38 Comparison of di raction behavior of a room with opening and a loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : : 40 2.39 Dispersion characteristics of a speaker. : : : : : : : : : : : : : 41 2.40 Standing wave produced by incident and re ected waves. : : : 41 iii
  • 8. 2.41 Simplest possible standing wave on a string. : : : : : : : : : : 42 2.42 Simplest standing wave on a string during one cycle. : : : : : 43 2.43 Second harmonic on a string showing position of nodes and antinodes. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 43 2.44 Third harmonic on a string clamped at both ends. : : : : : : 43 2.45 Setting up a standing wave in a tube. : : : : : : : : : : : : : 44 2.46 Simplest standing wave in a tube open at both ends. : : : : : 45 2.47 Second harmonic in tube open at both ends. : : : : : : : : : : 45 2.48 Fundamental in a tube. : : : : : : : : : : : : : : : : : : : : : 45 2.49 Tube open at one end excited by a tuning fork. : : : : : : : : 46 2.50 Fundamental in tube open at one end. : : : : : : : : : : : : : 46 2.51 Next more complicated standing wave; the third harmonic. : 47 2.52 Fifth harmonic. : : : : : : : : : : : : : : : : : : : : : : : : : : 47 2.53 Standing wave in a tube 1 meter long; fundamental. : : : : : 47 2.54 Tube closed at both ends. : : : : : : : : : : : : : : : : : : : : 48 2.55 Fundamental of a tube closed at both ends. : : : : : : : : : : 48 2.56 Room where independent standing waves can be set up in the x, y, and z directions. : : : : : : : : : : : : : : : : : : : : : : 49 2.57 A drumhead
  • 9. xed at its edges and its fundamental mode of vibration. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 50 2.58 Overtone on a drumhead. : : : : : : : : : : : : : : : : : : : : 51 2.59 Standing wave pattern on a Chladni plate. : : : : : : : : : : : 51 2.60 Complex wave created by the superposition of a 100 Hz fun- damental and its fourth harmonic. : : : : : : : : : : : : : : : 52 2.61 Violin string plucked by a
  • 10. nger and producing all sorts of harmonics. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 53 2.62 Complex wave generated by plucking string. : : : : : : : : : : 54 2.63 Square wave; it is made up of many harmonics. : : : : : : : : 55 2.64 Spectrum of a square wave. : : : : : : : : : : : : : : : : : : : 56 2.65 Sawtooth wave and its harmonic content. : : : : : : : : : : : 57 2.66 Spectrum of a sawtooth wave. : : : : : : : : : : : : : : : : : : 58 2.67 A string bowed at its middle and harmonics which are excited. 59 2.68 String on a piano struck by hammer at a distance 1/10 the string length from one end. : : : : : : : : : : : : : : : : : : : 60 2.69 Vibrations of an object at di erent excitation frequencies. : : 60 2.70 Oscillations of a mass on a spring, undamped and damped when submersed in oil. : : : : : : : : : : : : : : : : : : : : : : 61 2.71 Resonance of wine glass excited by sound. : : : : : : : : : : : 61 iv
  • 11. 2.72 Beats caused by the combination of two waves with slightly di erent frequencies. : : : : : : : : : : : : : : : : : : : : : : : 62 3.1 Decibel meter. : : : : : : : : : : : : : : : : : : : : : : : : : : 64 3.2 Receiver with volume control marked in dB. : : : : : : : : : : 64 3.3 Response of human ears at the threshold of hearing. : : : : : 64 3.4 Response of human ears for various sound levels: Fletcher- Munson curves. : : : : : : : : : : : : : : : : : : : : : : : : : : 65 3.5 Outer ear approximated by a tube closed at one end. : : : : : 65 3.6 Measuring the frequency response of a speaker. : : : : : : : : 66 3.7 Frequency response of a speaker. : : : : : : : : : : : : : : : : 66 4.1 Role of loudspeaker. : : : : : : : : : : : : : : : : : : : : : : : 68 4.2 Distortion of spectrum of original waveform by non- at fre- quency response of speaker. : : : : : : : : : : : : : : : : : : : 69 4.3 Dispersion properties of speakers. : : : : : : : : : : : : : : : : 70 4.4 Two low frequency waves from speaker arriving at O. : : : : : 71 4.5 Two high frequency waves from speaker arriving at O. : : : : 72 4.6 Details of waves 2 and 1 at high frequencies. : : : : : : : : : : 73 4.7 Sound dispersion of a driver as the frequency is increased. : : 74 4.8 Division of audio spectrum for a three-way loudspeaker. : : : 75 4.9 Net e ect of subdividing the whole audio range into three sections. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 76 4.10 Subdivision of audio spectrum in a two-way system. : : : : : 76 4.11 Amount of sound produced depends on volume displacement. A is louder than B. : : : : : : : : : : : : : : : : : : : : : : : : 77 4.12 To produce same amount of sound by both drivers at the same frequency, the small one has to move through a larger distance than the big one. : : : : : : : : : : : : : : : : : : : : 78 4.13 Volume of air moved by loudspeaker as a function of frequency to produce same loudness of sound. : : : : : : : : : : : : : : : 79 4.14 Low frequency and high frequency simple pendulums doing di erent amounts of work per second for same amplitude of displacement. : : : : : : : : : : : : : : : : : : : : : : : : : : : 80 4.15 Balance between electrical power going to driver and the pro- duction of sound power and heat dissipation by driver. : : : : 80 4.16 Example of a loudspeaker whose eciency is less than 100%. 81 4.17 Basic cone speaker. : : : : : : : : : : : : : : : : : : : : : : : : 82 v
  • 12. 4.18 Comparison of cone-shape over at shape for mechanical strength when thin material is used. : : : : : : : : : : : : : : : : : : : 83 4.19 Modeling of diaphragm action by mass-spring oscillating sys- tem. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 84 4.20 Standing wave on diaphragm of driver. : : : : : : : : : : : : : 85 4.21 Standing wave around rim of diaphragm. : : : : : : : : : : : 85 4.22 Typical frequency response of a cone speaker. : : : : : : : : : 86 4.23 Bae problem in cone driver. : : : : : : : : : : : : : : : : : : 86 4.24 Front and rear of cone speakers are 180  out of phase. : : : : 87 4.25 Bae action. : : : : : : : : : : : : : : : : : : : : : : : : : : : 88 4.26 Two possible approaches for trapping rear sound in a speaker by means of an enclosure. : : : : : : : : : : : : : : : : : : : : 88 4.27 E ect of enclosure on frequency response of speaker. : : : : : 89 4.28 Reducing standing waves inside speaker enclosure. : : : : : : 90 4.29 Basic bass-re ex enclosure. : : : : : : : : : : : : : : : : : : : 91 4.30 Oscillating components of bass-re ex speaker. : : : : : : : : : 92 4.31 Splitting of original resonance into two new resonances in bass-re ex system. : : : : : : : : : : : : : : : : : : : : : : : : 93 4.32 Resonant behavior, in-phase and out-of-phase, motion of strongly coupled components of bass-re ex system. : : : : : : : : : : : 94 4.33 Coupled components of a bass-re ex speaker. : : : : : : : : : 95 4.34 Bass-re ex speaker using a passive radiator over the port. : : 96 4.35 Helmholtz resonator behaves like mass-spring system. : : : : 97 4.36 Bass-re ex speaker using a port or a duct. : : : : : : : : : : : 98 4.37 Acoustic labyrinth enclosure. : : : : : : : : : : : : : : : : : : 99 4.38 Change of frequency response of speaker when a small enclo- sure is used. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 100 4.39 E ect of small enclosure on frequency response of driver. : : : 101 4.40 Transfer of energy from a bob to one of equal mass, and to one of di erent mass. : : : : : : : : : : : : : : : : : : : : : : : 102 4.41 A horn for matching vibrations of a light diaphragm to a large volume of air. : : : : : : : : : : : : : : : : : : : : : : : : : : : 103 4.42 Low frequency response of a horn. : : : : : : : : : : : : : : : 103 4.43 Some common horn shapes. : : : : : : : : : : : : : : : : : : : 104 4.44 Folded horn. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 105 4.45 Two-way horn loudspeaker with bass-re ex enclosure. : : : : 106 4.46 Standing wave set up in a room with maxima and minima in sound pressure. : : : : : : : : : : : : : : : : : : : : : : : : : : 107 vi
  • 13. 4.47 Re ected waves by a wall appear to come from behind the wall since it acts like a mirror. : : : : : : : : : : : : : : : : : 107 4.48 Stereo coverage in a room. : : : : : : : : : : : : : : : : : : : : 108 4.49 Speaker phasing: speakers are in phase. : : : : : : : : : : : : 108 4.50 Speaker phasing: speakers are out of phase. : : : : : : : : : : 109 4.51 Geometry of a Bose 901 speaker. : : : : : : : : : : : : : : : : 109 4.52 E ect of equalizer on frequency response of Bose speakers. : : 110 4.53 Bass horn in Klipsch horn speaker. : : : : : : : : : : : : : : : 111 4.54 Graphic equalizer. : : : : : : : : : : : : : : : : : : : : : : : : 111 5.1 Example of an atom: a Helium atom. : : : : : : : : : : : : : 113 5.2 Forces between charged objects; like charges repel and unlike charges attract. : : : : : : : : : : : : : : : : : : : : : : : : : : 114 5.3 Charged ping-pong balls repelling each other. : : : : : : : : : 115 5.4 Electric
  • 14. eld produced by a charged object. : : : : : : : : : : 115 5.5 Electric
  • 15. eld between two charged plates. : : : : : : : : : : : 116 5.6 Examples of voltage sources: a battery, the output of a receiver.116 5.7 Electrostatic speaker: basic principle and actual speaker. : : : 117 5.8 Simpli
  • 16. ed version of an electrostatic speaker at equilibrium. : 117 5.9 Push-pull action by two plates on charged sheet. : : : : : : : 118 5.10 An electrostatic speaker. : : : : : : : : : : : : : : : : : : : : : 118 5.11 Some crystals under pressure produce positive and negative charges on surface. : : : : : : : : : : : : : : : : : : : : : : : : 119 5.12 Dimensional changes of a piezoelectric ceramic when a voltage is applied. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 119 5.13 Bending action of a double piezoelectric driver. : : : : : : : : 120 5.14 Pumping action of cone caused by bending of bimorph. : : : 120 5.15 Typical piezo horn. : : : : : : : : : : : : : : : : : : : : : : : : 121 5.16 Wire connected between two charged objects allows charges to be transferred. : : : : : : : : : : : : : : : : : : : : : : : : : 121 5.17 Flow of electric current from ampli
  • 17. er to speaker. : : : : : : : 122 5.18 Solid with atoms where electrons are tightly bound and which does not conduct electricity under normal circumstances. : : 122 5.19 Motion of one electron in a conductor in the presence of an electric
  • 18. eld. Changes of direction are due to scattering. : : : 123 5.20 Temperature dependence of the electrical resistance in a con- ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 124 5.21 Superconductivity at Tc below which the resistance is zero. : 124 vii
  • 19. 5.22 The resistance to current or to water ow increases as the length of a conductor or pipe increases. Resistance of 2 is double that of 1. : : : : : : : : : : : : : : : : : : : : : : : : : 125 5.23 By increasing the cross-sectional area of a conductor, resis- tance to current or water ow decreases. : : : : : : : : : : : : 125 5.24 Resistor with colored bands to specify its resistance value. : : 126 5.25 Pure silicon, silicon doped with arsenic, and silicon doped with gallium. : : : : : : : : : : : : : : : : : : : : : : : : : : : 126 5.26 Example of simple circuit. : : : : : : : : : : : : : : : : : : : : 126 5.27 Model using water for electric circuit. : : : : : : : : : : : : : 127 5.28 Comparison between DC and AC current. : : : : : : : : : : : 128 5.29 Representation of a sound wave by an AC electrical signal. : 128 5.30 Variable resistance between X and Y. : : : : : : : : : : : : : 129 5.31 Fuse to protect speaker. : : : : : : : : : : : : : : : : : : : : : 129 5.32 Two speakers connected in series to one channel of ampli
  • 20. er. 129 5.33 Model of series circuit. : : : : : : : : : : : : : : : : : : : : : : 130 5.34 Parallel connection of two speakers to an ampli
  • 21. er. : : : : : : 130 5.35 Model of parallel connections. : : : : : : : : : : : : : : : : : : 131 5.36 Parallel connections of hi-
  • 22. components to house electrical outlet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 131 5.37 Response of cone speaker to a force. : : : : : : : : : : : : : : 132 5.38 Coil used to produce a magnetic
  • 23. eld when a current ows through it. It has inductance. : : : : : : : : : : : : : : : : : : 133 5.39 Frequency dependence of impedance associated with induc- tance. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 134 5.40 Charging of a capacitor. : : : : : : : : : : : : : : : : : : : : : 134 5.41 Charging of a capacitor when polarity of voltage source is reversed. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 135 5.42 Frequency dependence of impedance due to capacitance. : : : 135 5.43 Inductance in series with woofer prevents high frequencies from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 136 5.44 Capacitance in series with tweeter. It prevents low frequencies from reaching it. : : : : : : : : : : : : : : : : : : : : : : : : : 136 5.45 Capacitance and inductance in series with mid-range speaker to prevent the high and low frequencies from reaching it. : : : 137 5.46 Impedance curve of driver. : : : : : : : : : : : : : : : : : : : : 137 6.1 Importance of ampli
  • 24. er in hi-
  • 25. system. : : : : : : : : : : : : : 139 6.2 Basic ampli
  • 26. er. : : : : : : : : : : : : : : : : : : : : : : : : : : 139 viii
  • 27. 6.3 Ampli
  • 28. er command for more current. : : : : : : : : : : : : : 140 6.4 Ampli
  • 29. er command for less current. : : : : : : : : : : : : : : 140 6.5 Semiconductor junction. : : : : : : : : : : : : : : : : : : : : : 141 6.6 Reverse-biased semiconductor junction. : : : : : : : : : : : : 141 6.7 Forward-biased semiconductor junction. : : : : : : : : : : : : 142 6.8 Symbol for diodes and its characteristics. : : : : : : : : : : : 142 6.9 Recti
  • 30. er action of a diode when an AC voltage is applied. : : 142 6.10 Diagram of transistor and its circuit symbol for two possibilities.143 6.11 Ampli
  • 31. er action of transistor in a circuit compared to control of water ow. : : : : : : : : : : : : : : : : : : : : : : : : : : : 143 6.12 Function of an ampli
  • 32. er. : : : : : : : : : : : : : : : : : : : : : 144 6.13 Ampli
  • 33. er integrated on a chip. : : : : : : : : : : : : : : : : : 144 6.14 Operational ampli
  • 34. er with negative feedback. : : : : : : : : : 144 6.15 Negative feedback corrects uctuations in gain. : : : : : : : : 145 6.16 Positive feedback in large hall with a mike and a loudspeaker system driven by mike. : : : : : : : : : : : : : : : : : : : : : : 145 6.17 Volume control. : : : : : : : : : : : : : : : : : : : : : : : : : : 146 6.18 Comparison of potentiometer action with energy of a ball on a ladder. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 146 6.19 Bass and Treble controls. : : : : : : : : : : : : : : : : : : : : 147 6.20 E ect on signal spectrum of Bass and Treble controls. : : : : 148 6.21 Action of LOW and HIGH
  • 35. lters with 6 dB/octave attenua- tion, and also with 18 db/octave attenuation. : : : : : : : : : 148 6.22 Harmonic distortion by ampli
  • 36. er. : : : : : : : : : : : : : : : : 149 6.23 Non-linear gain of ampli
  • 37. er. : : : : : : : : : : : : : : : : : : : 149 6.24 IM distortion in ampli
  • 38. er. : : : : : : : : : : : : : : : : : : : : 150 6.25 Distortion increases sharply about power rating of ampli
  • 39. er. : 150 6.26 Clipping of waveform by ampli
  • 40. er at high output levels be- yond the rated value. : : : : : : : : : : : : : : : : : : : : : : : 151 6.27 E ect of noise from ampli
  • 41. er. : : : : : : : : : : : : : : : : : : 151 6.28 Comparing 2 ampli
  • 42. ers with the same specs. Even though their specs are the same, the ampli
  • 43. ers will sound di erent. : 152 6.29 A-weighted method of measuring noise. : : : : : : : : : : : : 152 7.1 E ect of current in a wire on compasses around it. : : : : : : 154 7.2 Bar magnet has a north pole and a south pole. : : : : : : : : 154 7.3 Cutting a bar magnet produces shorter magnets each with its own respective north and south poles. : : : : : : : : : : : : : 154 7.4 Magnetic dipole is the basic unit of magnetism. : : : : : : : : 155 ix
  • 44. 7.5 Unmagnetized piece of iron. : : : : : : : : : : : : : : : : : : : 155 7.6 Alignment of domains in a piece of iron by a bar magnet. Iron becomes magnetized. : : : : : : : : : : : : : : : : : : : : : : : 156 7.7 Magnetic
  • 45. eld around a bar magnet and a wire carrying a current. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 156 7.8 Increasing the magnetic
  • 46. eld produced by a current in a wire: by forming a loop, and by using many loops. : : : : : : : : : 157 7.9 An electromagnet. : : : : : : : : : : : : : : : : : : : : : : : : 157 7.10 Determination of direction of magnetic
  • 47. eld using
  • 48. rst left- hand rule. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 158 7.11 Rule for determining direction of magnetic
  • 49. eld in an electro- magnet. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 158 7.12 First left-hand rule and how a cone speaker works. : : : : : : 159 7.13 Force on wire carrying a current in a magnetic
  • 50. eld. : : : : : 159 7.14 The second left-hand rule showing direction of force on wire carrying a current in a magnetic
  • 51. eld. : : : : : : : : : : : : : 160 7.15 Direction of force depends on orientation of current with re- spect to magnetic
  • 52. eld. : : : : : : : : : : : : : : : : : : : : : 161 7.16 A Heil Speaker. : : : : : : : : : : : : : : : : : : : : : : : : : : 162 7.17 One set of folds in Heil speaker. : : : : : : : : : : : : : : : : : 163 7.18 Magnetic Planar Speaker. : : : : : : : : : : : : : : : : : : : : 164 7.19 Forces on diaphragm when current direction is as indicated. : 165 7.20 A bar magnet moving into a coil induces an electric current in that coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 165 7.21 Induced current in coil by moving magnet. : : : : : : : : : : : 166 7.22 Signi
  • 53. cance of relative motion between magnet and coil. : : : 167 7.23 Direction of induced current (wrong). : : : : : : : : : : : : : 167 7.24 Direction of induced current (correct). : : : : : : : : : : : : : 168 7.25 Schematic of a transformer and its circuit symbol. : : : : : : 169 7.26 Step-up transformer. : : : : : : : : : : : : : : : : : : : : : : : 170 7.27 Step-down transformer. : : : : : : : : : : : : : : : : : : : : : 170 7.28 Schematic of microphone based on Faraday's law of induction. 171 7.29 Exercise 7.14. : : : : : : : : : : : : : : : : : : : : : : : : : : : 171 7.30 Exercise 7.15. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172 7.31 Exercise 7.18. : : : : : : : : : : : : : : : : : : : : : : : : : : : 172 8.1 Electric Field around charged ping-pong ball. : : : : : : : : : 174 8.2 Oscillating charged ball. : : : : : : : : : : : : : : : : : : : : : 174 x
  • 54. 8.3 Generation of electromagnetic waves at two di erent frequen- cies. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 175 8.4 Spectrum of electromagnetic waves. : : : : : : : : : : : : : : : 175 8.5 Electromagnetic waves are transverse waves with oscillating electric and magnetic
  • 55. elds. : : : : : : : : : : : : : : : : : : : 176 8.6 Production of electromagnetic waves by oscillating electrons in antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 176 8.7 Generation of electric and magnetic
  • 56. elds by antenna. : : : : 177 8.8 Production of electromagnetic waves by antenna. : : : : : : : 177 8.9 Some examples of modulation. : : : : : : : : : : : : : : : : : 178 8.10 Amplitude modulation. : : : : : : : : : : : : : : : : : : : : : 178 8.11 Carrier and audio signals broadcast by two stations. : : : : : 179 8.12 Spectrum of an AM carrier at frequency f when modulated by audio signal. : : : : : : : : : : : : : : : : : : : : : : : : : : 179 8.13 Audio frequencies modulating carrier. : : : : : : : : : : : : : 180 8.14 Spectrum of frequencies on carrier for audio frequencies up to 5 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 180 8.15 Spectrum of frequencies due to modulation of carrier. : : : : 181 8.16 Frequency modulation (FM). : : : : : : : : : : : : : : : : : : 181 8.17 A low frequency and a high frequency audio signal frequency modulating a carrier. : : : : : : : : : : : : : : : : : : : : : : : 182 8.18 A loud and a quiet audio signal frequency modulating a carrier.183 8.19 Action of limiter in FM. : : : : : : : : : : : : : : : : : : : : : 184 8.20 Pre-emphasis in FM broadcasting. : : : : : : : : : : : : : : : 184 8.21 Information brought to tuner on carrier. : : : : : : : : : : : : 185 8.22 De-emphasis of audio information to reduce high frequency noise. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 185 8.23 Elements of radio communications. : : : : : : : : : : : : : : : 186 8.24 Superheterodyne receiver. : : : : : : : : : : : : : : : : : : : : 186 8.25 Processing part of AM signal with a simple diode and
  • 57. lters. 186 8.26 Audio information which will modulate carrier in stereo broad- casting. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 187 8.27 Alternating current in antenna produces electromagnetic wave.188 8.28 Electric
  • 58. eld around charged antenna wires is similar to that between charged capacitor plates. : : : : : : : : : : : : : : : : 189 8.29 Magnetic
  • 59. elds around a wire and antenna with current. : : : 189 8.30 Development of a standing wave on antenna. : : : : : : : : : 190 8.31 Comparison of standing wave on antenna to that of a string. 191 xi
  • 60. 8.32 Radiation pattern of electric
  • 61. eld around half-wave dipole antenna. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 192 8.33 Polar graph representation of radiation pattern around half- wave dipolar antenna. : : : : : : : : : : : : : : : : : : : : : : 192 8.34 Basic elements of a grounded vertical antenna. : : : : : : : : 193 8.35 Quarter-wave antenna. : : : : : : : : : : : : : : : : : : : : : : 193 8.36 Total antenna length is made shorter by inserting a coil in series. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 194 8.37 When the electric
  • 62. eld of radio wave is vertical, the receiving antenna should also be vertical. : : : : : : : : : : : : : : : : : 195 8.38 Loop antenna detects the magnetic
  • 63. eld part of radio wave. : 195 8.39 Two common loop antennas. : : : : : : : : : : : : : : : : : : 196 8.40 Vertically polarized radio wave. : : : : : : : : : : : : : : : : : 196 8.41 Horizontally polarized radio wave. : : : : : : : : : : : : : : : 197 8.42 Broadcasting with circular polarization. : : : : : : : : : : : : 197 8.43 Low frequency ground wave follows curvature of earth. : : : : 198 8.44 Direct (line-of-sight) mode of propagation. : : : : : : : : : : : 198 8.45 Earth's ionosphere layers. : : : : : : : : : : : : : : : : : : : : 199 8.46 Sky wave world communications. : : : : : : : : : : : : : : : : 199 8.47 Two-hop transmission of radio wave using ionosphere. : : : : 200 8.48 Communication using a satellite. : : : : : : : : : : : : : : : : 200 8.49 Selectivity relates to how well alternate channels are rejected. 201 8.50 Direct and re ected waves from a broadcasting station. : : : 201 8.51 Capture ratio in tuner. : : : : : : : : : : : : : : : : : : : : : : 201 9.1 Record with grooves representing mechanically engraved waves.203 9.2 Phono playback systems. : : : : : : : : : : : : : : : : : : : : : 204 9.3 Stereo with only one stylus. : : : : : : : : : : : : : : : : : : : 205 9.4 A stereo moving magnet phono cartridge. : : : : : : : : : : : 206 9.5 Unmagnetized and magnetized magnetic material. : : : : : : 206 9.6 Magnetic
  • 64. eld produced by a coil when current ows through it. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 207 9.7 Alignment of domains in a magnetic material. : : : : : : : : : 208 9.8 Behavior of magnetic material in a coil whose current is in- creased and decreased to zero. : : : : : : : : : : : : : : : : : : 209 9.9 Memory is destroyed by reversed current in coil. : : : : : : : 210 9.10 Hysteresis curve of magnetic material. : : : : : : : : : : : : : 211 9.11 Groups of magnetic materials. : : : : : : : : : : : : : : : : : : 212 9.12 Side and top views of magnetic tape. : : : : : : : : : : : : : : 213 xii
  • 65. 9.13 Magnetic particle of gamma { Iron (III) Oxide as used on tapes.213 9.14 Recording head aligning magnetic domains on tape. : : : : : 214 9.15 Analog recording on a magnetic tape. : : : : : : : : : : : : : 215 9.16 Recorded information on magnetic tape. : : : : : : : : : : : : 216 9.17 Playback head for reading information on a tape. : : : : : : : 216 9.18 Playback head reading signals. : : : : : : : : : : : : : : : : : 216 9.19 Order of heads on a tape deck. : : : : : : : : : : : : : : : : : 217 9.20 Recording on material with magnetic hysteresis. : : : : : : : 217 9.21 Recording a signal on a tape. : : : : : : : : : : : : : : : : : : 218 9.22 Ideal magnetic characteristics for tape | linear behavior. : : 219 9.23 Useful region on hysteresis curve for magnetic recording. : : : 220 9.24 Recording on magnetic tape with bias. : : : : : : : : : : : : : 221 9.25 Details of heads for magnetic recording. : : : : : : : : : : : : 222 9.26 Frequency dependence of output from playback head. : : : : 222 9.27 Output from playback head as a function of frequency for various gap sizes and tape speeds. : : : : : : : : : : : : : : : 223 9.28 Equalization in playback. : : : : : : : : : : : : : : : : : : : : 223 9.29 Equalization in recording. : : : : : : : : : : : : : : : : : : : : 224 9.30 Typical musical spectrum. : : : : : : : : : : : : : : : : : : : : 224 9.31 Frequency response at di erent recording levels. : : : : : : : : 225 9.32 Exercise 9.4. : : : : : : : : : : : : : : : : : : : : : : : : : : : : 225 10.1 Sound wave and its analog representation as a voltage. : : : : 227 10.2 Grooves on a record representing analog signals. : : : : : : : 228 10.3 Distortion of analog signal by dirt stuck between playback head and tape. : : : : : : : : : : : : : : : : : : : : : : : : : : 229 10.4 Original number 2 and worn out number 2; basic information is not lost when number is worn out. : : : : : : : : : : : : : : 229 10.5 (a) Analog signal, decimal scale (b) Analog signal, binary scale.230 10.6 20 Hz wave will get more samples per wave than a 200 Hz wave.230 10.7 Aliasing due to inadequate sampling rate. : : : : : : : : : : : 231 10.8 Audio spectrum and sideband frequencies due to sampling. : 232 10.9 Sample and hold of a signal for digitizing. : : : : : : : : : : : 233 10.10 Multiplexing of left and right channels. : : : : : : : : : : : : 233 10.11 Digitizing a signal. : : : : : : : : : : : : : : : : : : : : : : : : 234 10.12 Output of D-A converter. : : : : : : : : : : : : : : : : : : : : 234 10.13 Output of low-pass
  • 66. lter. : : : : : : : : : : : : : : : : : : : : 235 10.14 Main features of playback of digital signal. : : : : : : : : : : 235 10.15 Details of information on a CD. : : : : : : : : : : : : : : : : 236 xiii
  • 67. 10.16 Interference between light beam re ected from pit and from at. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 237 10.17 Focusing action of a laser beam by lens. : : : : : : : : : : : : 237 10.18 Reduced e ect of surface defect on CD. : : : : : : : : : : : : 238 10.19 Laser spot focused on disc data. : : : : : : : : : : : : : : : : 239 10.20 Three-beam detection; one for read-out and two beams for tracking. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 240 10.21 Randomly polarized beam and plane-polarized beam. : : : : 241 10.22 Path of laser beam and role of its polarization. : : : : : : : : 242 10.23 Coherent and incoherent beams of light. : : : : : : : : : : : : 243 10.24 Semiconductor laser. : : : : : : : : : : : : : : : : : : : : : : : 244 10.25 E ect of 2-times and 4-times oversampling. : : : : : : : : : : 245 10.26 Shock-proof memory in mini-disc. : : : : : : : : : : : : : : : 246 11.1 Magnetic digital signals recorded vertically on a mini disc. : : 248 11.2 Recording digital signals on a mini disc. : : : : : : : : : : : : 248 11.3 Kerr e ect: plane of polarization of light beam rotates upon re ection from a magnetized surface. : : : : : : : : : : : : : : 249 11.4 Read-out of digital information using Kerr e ect. Magnetic
  • 68. eld direction a ects plane of polarization of re ected laser beam. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 249 11.5 Di erence in read-out between pre-recorded and recordable mini-discs. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 250 11.6 Section of a recordable mini disc. : : : : : : : : : : : : : : : : 251 11.7 Layered structure of recordable mini disc. : : : : : : : : : : : 251 11.8 Track pattern in DCC tape. : : : : : : : : : : : : : : : : : : : 252 11.9 The playback head reads only a portion of the recorded track. 252 11.10 Threshold of hearing curve. : : : : : : : : : : : : : : : : : : : 252 11.11 Sounds which will be recorded by PASC and masking of quiet passages. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 253 11.12 Representation of digital signal on magnetic tape. : : : : : : 253 11.13 Helical recording with rotating heads. : : : : : : : : : : : : : 254 11.14 Tape contact to rotating head. : : : : : : : : : : : : : : : : : 255 11.15 Time compression to reduce wrap angle. : : : : : : : : : : : 256 11.16 Guard band between tracks on analog tape reduces cross-talk.257 11.17 Azimuthal recording. : : : : : : : : : : : : : : : : : : : : : : 257 11.18 Digital information on magnetic tape recorded longitudinally. 258 11.19 Arrangement of signals on a tape. : : : : : : : : : : : : : : : 259 11.20 Exercise 11.7. : : : : : : : : : : : : : : : : : : : : : : : : : : 259 xiv
  • 69. 12.1 Sources of heating in hi-
  • 70. due to mechanical friction and elec- trical friction". : : : : : : : : : : : : : : : : : : : : : : : : : : 261 12.2 Electrical friction" causes heating in ampli
  • 71. er components and voice coil. : : : : : : : : : : : : : : : : : : : : : : : : : : : 262 12.3 Two types of thermometers: alcohol expansion thermometer and gas thermometer. : : : : : : : : : : : : : : : : : : : : : : 263 12.4 Temperature dependence of electric resistance of a semicon- ductor. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 264 12.5 Basic circuit for resistance thermometer. : : : : : : : : : : : : 264 12.6 Heating of spot on mini-disc for recording. : : : : : : : : : : : 265 12.7 Heat conduction along a bar between a hot body and a cold one. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 265 12.8 Thermal resistance depends on length of heat conductor. : : : 266 12.9 Thermal resistance depends inversely on cross-sectional area of heat conductor. : : : : : : : : : : : : : : : : : : : : : : : : 267 12.10 Transfer of heat in air by convection. : : : : : : : : : : : : : 268 12.11 Object at temperature T emits electromagnetic waves. : : : 268 12.12 Thermal expansion of an object when heated. : : : : : : : : 269 12.13 Bimetallic strip and its behavior when heated or cooled. : : : 269 12.14 Mounting of transistor and diode on heat sink to transfer heat away from devices by heat conduction. : : : : : : : : : : 270 12.15 Heat removal by convection and radiation. : : : : : : : : : : 271 12.16 Action of circuit-breaker when too hot. : : : : : : : : : : : : 271 12.17 Thermo-magnetic recording on mini-Disc. : : : : : : : : : : : 272 13.1 Speed of tape past recording head. : : : : : : : : : : : : : : : 274 13.2 Time for a radio wave to go around the Earth at the equator. 274 13.3 Speed of a recorded signal is the same at X and at Y; their velocities are di erent. : : : : : : : : : : : : : : : : : : : : : : 275 13.4 Force on voice coil giving it a push or a pull depending on direction of current in voice coil. : : : : : : : : : : : : : : : : 276 13.5 Force on tape by capstan-pinch roller. : : : : : : : : : : : : : 277 13.6 Static friction-force pulling on tape. : : : : : : : : : : : : : : 277 13.7 Releasing a CD from its case by applying a pressure on the clips with a
  • 72. nger. : : : : : : : : : : : : : : : : : : : : : : : : 278 13.8 Inertia of a tweeter is less than that of a woofer. : : : : : : : 279 13.9 Outer ear; ear drum's inertia limits response at frequencies above 20 kHz. : : : : : : : : : : : : : : : : : : : : : : : : : : : 280 xv
  • 73. 13.10 Adjusted weight in cartridge for helping the stylus to track the groove in phono record. : : : : : : : : : : : : : : : : : : : 280 13.11 Force of clamped magnet on a voice coil accelerates diaphragm in loudspeaker. Force of clamped magnet on focus coil accel- erates focus lens in CD player. : : : : : : : : : : : : : : : : : 281 13.12 Re ection of a pulse on a string clamped at wall and its inversion. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 282 13.13 Force on voice coil and force on magnet. : : : : : : : : : : : 283 13.14 Waves recorded on a phono record and a CD. : : : : : : : : : 284 13.15 Distances covered along outer track and inner track on a phono record. : : : : : : : : : : : : : : : : : : : : : : : : : : : 285 13.16 Frequency of rotation of a CD is made higher near the inner edge and lower near the outer edge to maintain constant linear speed on a tracks. : : : : : : : : : : : : : : : : : : : : : : : : 286 13.17 Rotation of drum head relative to magnetic tape in DAT. : : 286 13.18 When same force is applied to the CD case lid, it is easier to open the lid near the edge because torque is larger there. : : 287 13.19 For the same force exerted on lid, the torque is larger in B than in A. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 288 13.20 Moment of inertia of a CD is larger than that of a mini-Disc. 288 xvi
  • 74. Chapter 1 Introduction to Hi-Fi 1
  • 75. CHAPTER 1. INTRODUCTION TO HI-FI 2 Microphone R Record L R Microphone Playback Speakers L Figure 1.1: Stereo process in recording and playback.
  • 76. CHAPTER 1. INTRODUCTION TO HI-FI 3 Stereo Right Surround Right Center Speaker Surround Left Stereo Left Figure 1.2: Surround sound reproduction of audio information. Left Left Sources Store (Record) of Stereo or Stereo Sound Transmit Right Right Figure 1.3: Storage or transmission of sound in stereo.
  • 77. CHAPTER 1. INTRODUCTION TO HI-FI 4 Right Right Sources of Playback Sound Left Left Figure 1.4: Playback process in stereo. Tuner + Pre-Amplifier = Receiver + Power Amplifier Figure 1.5: Elements of a receiver.
  • 78. CHAPTER 1. INTRODUCTION TO HI-FI 5 Antenna Phono Tape Deck Receiver CD DAT Figure 1.6: Example of basic connections to a receiver. Pre-Amplifier + = Integrated Amplifier Power Amplifier Figure 1.7: Elements of an integrated ampli
  • 79. er.
  • 80. CHAPTER 1. INTRODUCTION TO HI-FI 6 Antenna Tuner CD Integrated Phono Amplifier Tape Deck DAT Figure 1.8: Connections to an integrated ampli
  • 81. er. Pre-Amp + Power Amplifier Separate components Figure 1.9: All separate approach.
  • 82. CHAPTER 1. INTRODUCTION TO HI-FI 7 Antenna Tuner CD Power Pre-Amp Phono Amplifier Tape Deck DAT Figure 1.10: Connections in all-separate approach.
  • 83. CHAPTER 1. INTRODUCTION TO HI-FI 8 Audio Input Audio Video A/V Receiver VCR VCR Output Stereo Speaker L R Output Video Monitor Figure 1.11: Basic A/V System.
  • 84. CHAPTER 1. INTRODUCTION TO HI-FI 9 L R Surround Speaker Output Audio Input A/V Receiver Audio VCR Video Output VCR Stereo Speaker L R Output Video Monitor Figure 1.12: A/V receiver driving a surround-sound system.
  • 85. CHAPTER 1. INTRODUCTION TO HI-FI 10 Tape Deck In Out Out for In from Recording Tape Deck Inputs In Out Out Selector Switch Tape Tone Controls Monitor Switch Figure 1.13: Details of the tape monitor switch when listening to a sound source with available tape recording.
  • 86. CHAPTER 1. INTRODUCTION TO HI-FI 11 Tape Deck In Out Out for In from Recording Tape Deck Inputs In Out Out Selector Switch Tape Tone Controls Monitor Switch Figure 1.14: Listening to a tape; tape switch in.
  • 87. CHAPTER 1. INTRODUCTION TO HI-FI 12 Center Channel Speaker R Left TV Right Front Front Speaker Speaker Video A/V Receiver Video Audio VCR Left Right Surround Surround Speaker Speaker Figure 1.15: A/V receiver with Dolby Pro Logic processor.
  • 88. CHAPTER 1. INTRODUCTION TO HI-FI 13 A B C Amplitude of Signal Time Time Time D E F Amplitude of Signal Time Time Time G Amplitude of Signal Time Figure 1.16: Various wave forms.
  • 89. Chapter 2 Waves 14
  • 90. CHAPTER 2. WAVES 15 Figure 2.1: Phono record and an enlarged groove showing engraved wave representing sound. Displacement up Equilibrium Position Distance No Waves Waves Displacement down Figure 2.2: Simpli
  • 91. ed picture of a water wave; displaced water as a function of position.
  • 92. CHAPTER 2. WAVES 16 Displacement up Distance 1 Wave Displacement down Figure 2.3: Details of one wave as a function of position. Displacement Distance Large Amplitude Small Amplitude Figure 2.4: Large and small amplitude waves.
  • 93. CHAPTER 2. WAVES 17 + Displacement from Time Equilibrium - Figure 2.5: Time dependence of displacement of a point on a water wave. + Displacement Time 1 Period - Figure 2.6: Displacement as a function of time; time required to complete one wave.
  • 94. CHAPTER 2. WAVES 18 String Clamp Clamp Figure 2.7: Transverse wave on a string. Figure 2.8: Longitudinal waves along a solid bar. Wave 1 Wave 2 Result Position + Position = Position Figure 2.9: Addition of two waves.
  • 95. CHAPTER 2. WAVES 19 Sound No Sound Air Vacuum Bell Jar Figure 2.10: Sound requires a medium in which to propagate; in a vacuum there is no sound propagation. Diaphragm Diaphragm Direct Radiator Speaker Drum Figure 2.11: Direct radiator speaker can move air like a drumhead.
  • 96. CHAPTER 2. WAVES 20 Air at Atmospheric Pressure Speaker ≈ 14.7 lbs./sq.in. Increase in Pressure = Condensation Speaker Motion Figure 2.12: Generation of sound by loudspeaker.
  • 97. CHAPTER 2. WAVES 21 Rarefaction Condensation Motion Speaker Motion Pressure Change Equilibrium Pressure at ≈ 14.7 lbs./sq.in. 1 Wave Figure 2.13: Disturbances created by loudspeaker; pressure changes cause sound. Air Pressure Increase Equilibrium Air Pressure Distance Vibrating Speaker Air Pressure Louder Decrease Sound Figure 2.14: Representation of sound created by a loudspeaker.
  • 98. CHAPTER 2. WAVES 22 Amplitude Amplitude Wave Y Wave X 2 2 1 1 0 0 -1 Distance -1 Distance -2 -2 Figure 2.15: Wave Y has 4 times the power of wave X, but their amplitudes di er only by a factor of 2. al orm N Obstacle Incoming Wave Angle of Incidence Reflected Wave Angle of Reflection Figure 2.16: Re ection of a wave by an obstacle or a di erent medium.
  • 99. CHAPTER 2. WAVES 23 Sound Produced Sound Power Time 0 Speaker produces a Pulse of Sound Figure 2.17: Speaker producing a pulse of sound in a hall.
  • 100. CHAPTER 2. WAVES 24 Reflected Direct Sound Produced Amount Direct of Sound Reflected Time 0 Reverberant Sound Figure 2.18: Paths of direct and re ected sound in a hall.
  • 101. CHAPTER 2. WAVES 25 Reflected Sound (Reverberant) Direct Sound Figure 2.19: Direct and reverberant sound in a hall.
  • 102. CHAPTER 2. WAVES 26 Amount of Sound Reverberant Direct Distance from Source Source About 6 meters from Stage Figure 2.20: Direct and reverberant sound contributions to sound in a hall.
  • 103. CHAPTER 2. WAVES 27 1 2 3 4 Figure 2.21: Sound radiated by a speaker; as one moves away the intensity decreases.
  • 104. CHAPTER 2. WAVES 28 1 2 Figure 2.22: Sound intensity through surface 2 is di erent from that of 1.
  • 105. CHAPTER 2. WAVES 29 At Rest Relative Motion Figure 2.23: Observer and source at rest and in relative motion.
  • 106. CHAPTER 2. WAVES 30 Speaker moving Speaker moving toward Listener away from Listener 100 Hz Signal 1000 Hz Signal Increase in Decrease in Frequency heard by Frequency heard by Listener Listener Figure 2.24: Doppler E ect produced by speaker producing simultaneously 100 Hz and 1,000 Hz sound waves.
  • 107. CHAPTER 2. WAVES 31 Hot Air Incoming Sound Wave Cold Air Figure 2.25: Sound wave in cold air entering hot air. Hot Air Normal Cold Air Figure 2.26: Refraction of a sound wave.
  • 108. CHAPTER 2. WAVES 32 Hot Air Normal Critical Angle Cold Air Figure 2.27: Above a critical angle of incidence there is only re ection.
  • 109. CHAPTER 2. WAVES 33 Plastic Sound Air Waves Figure 2.28: Sound travels in a curved hollow plastic tube by multiple re- ections.
  • 110. CHAPTER 2. WAVES 34 Displacement Time Figure 2.29: Sound wave produced by a musical group; a complex wave. Displacement 0 Time Figure 2.30: Simple sine waveform.
  • 111. CHAPTER 2. WAVES 35 90˚ 90˚ 360˚ Time or 180˚ 360˚ 180˚ Position 270˚ 270˚ Figure 2.31: Comparison between one full wave and one rotation of a circle. Disturbance Disturbance Disturbance 0 Time + 0 Time = 0 Time or or or Position Position Position Figure 2.32: Addition of two waves. Displacement Displacement Displacement 0 Position + 0 Position = 0 Position Figure 2.33: Addition of two waves out of phase by 180 degrees.
  • 112. CHAPTER 2. WAVES 36 In Phase Figure 2.34: Constructive interference.
  • 113. CHAPTER 2. WAVES 37 Out of Phase Figure 2.35: Destructive interference.
  • 114. CHAPTER 2. WAVES 38 Figure 2.36: Obstacle with aperture receiving high frequency waves.
  • 115. CHAPTER 2. WAVES 39 Figure 2.37: Low frequency behavior of obstacle and aperture.
  • 116. CHAPTER 2. WAVES 40 Figure 2.38: Comparison of di raction behavior of a room with opening and a loudspeaker.
  • 117. CHAPTER 2. WAVES 41 High Frequencies Low Frequencies Figure 2.39: Dispersion characteristics of a speaker. Incident Wave Reflected Wave Result Figure 2.40: Standing wave produced by incident and re ected waves.
  • 118. CHAPTER 2. WAVES 42 Figure 2.41: Simplest possible standing wave on a string.
  • 119. CHAPTER 2. WAVES 43 1/2 Wave Figure 2.42: Simplest standing wave on a string during one cycle. Displacement: Node Antinode Node Antinode Node Figure 2.43: Second harmonic on a string showing position of nodes and antinodes. Third Harmonic Figure 2.44: Third harmonic on a string clamped at both ends.
  • 120. CHAPTER 2. WAVES 44 Or Figure 2.45: Setting up a standing wave in a tube.
  • 121. CHAPTER 2. WAVES 45 1/2 Wave Displacement Node Displacement Antinode Antinode Figure 2.46: Simplest standing wave in a tube open at both ends. Second Harmonic Figure 2.47: Second harmonic in tube open at both ends. 1/2 Wave 1 Meter Figure 2.48: Fundamental in a tube.
  • 122. CHAPTER 2. WAVES 46 Figure 2.49: Tube open at one end excited by a tuning fork. 1/4 Wave Displacement Displacement Antinode Node Figure 2.50: Fundamental in tube open at one end.
  • 123. CHAPTER 2. WAVES 47 3/4 Wave 1/4 Wave 1/4 Wave 1/4 Wave Figure 2.51: Next more complicated standing wave; the third harmonic. Fifth Harmonic Figure 2.52: Fifth harmonic. 1/4 Wave 1 Meter Figure 2.53: Standing wave in a tube 1 meter long; fundamental.
  • 124. CHAPTER 2. WAVES 48 Figure 2.54: Tube closed at both ends. 1/2 Wave Displacement Antinode Displacement Node Node Figure 2.55: Fundamental of a tube closed at both ends.
  • 125. CHAPTER 2. WAVES 49 z e av 2 W 1/ 1/2 Wave y 1/2 Wave x Figure 2.56: Room where independent standing waves can be set up in the x, y, and z directions.
  • 126. CHAPTER 2. WAVES 50 Figure 2.57: A drumhead
  • 127. xed at its edges and its fundamental mode of vibration.
  • 128. CHAPTER 2. WAVES 51 Figure 2.58: Overtone on a drumhead. Figure 2.59: Standing wave pattern on a Chladni plate.
  • 129. CHAPTER 2. WAVES 52 Complex Wave + = 100 Hz 400 Hz Figure 2.60: Complex wave created by the superposition of a 100 Hz funda- mental and its fourth harmonic.
  • 130. CHAPTER 2. WAVES 53 Figure 2.61: Violin string plucked by a
  • 131. nger and producing all sorts of harmonics.
  • 132. CHAPTER 2. WAVES 54 Displacement Time Figure 2.62: Complex wave generated by plucking string.
  • 133. CHAPTER 2. WAVES 55 Amplitude Time Frequency Relative Amplitude f 1 3f 1/3 5f 1/5 ... ... ... nf 1/n n = odd integer Figure 2.63: Square wave; it is made up of many harmonics.
  • 134. CHAPTER 2. WAVES 56 1.0 Relative Amplitude 0.5 0 Harmonics 1 2 3 4 5 6 7 Figure 2.64: Spectrum of a square wave.
  • 135. CHAPTER 2. WAVES 57 Amplitude Time Frequency Relative Amplitude f 1 2f 1/2 3f 1/3 4f 1/4 5f 1/5 ... ... ... nf 1/n n = integer Figure 2.65: Sawtooth wave and its harmonic content.
  • 136. CHAPTER 2. WAVES 58 1.0 Relative Amplitude 0.5 0 Harmonics 1 2 3 4 5 6 7 8 Figure 2.66: Spectrum of a sawtooth wave.
  • 137. CHAPTER 2. WAVES 59 Figure 2.67: A string bowed at its middle and harmonics which are excited.
  • 138. CHAPTER 2. WAVES 60 Hammer Figure 2.68: String on a piano struck by hammer at a distance 1/10 the string length from one end. Amplitude Frequency Natural Frequency Figure 2.69: Vibrations of an object at di erent excitation frequencies.
  • 139. CHAPTER 2. WAVES 61 Oil Undamped Damped Figure 2.70: Oscillations of a mass on a spring, undamped and damped when submersed in oil. Ping Pong Ball Figure 2.71: Resonance of wine glass excited by sound.
  • 140. CHAPTER 2. WAVES 62 F1 Time F2 Time Time Resultant Figure 2.72: Beats caused by the combination of two waves with slightly di erent frequencies.
  • 141. Chapter 3 Decibels 63
  • 142. CHAPTER 3. DECIBELS 64 dB Figure 3.1: Decibel meter. 0 dB -70 dB Volume Receiver Figure 3.2: Receiver with volume control marked in dB. Sound Pressure Level (dB) 140 Threshold of Pain 120 100 80 Range of 60 Human 40 Hearing 20 Threshold of Hearing 0 20 100 1,000 10,000 Frequency (Hz) Figure 3.3: Response of human ears at the threshold of hearing.
  • 143. CHAPTER 3. DECIBELS 65 Sound Pressure Level (dB) 140 130 dB 120 120 dB 110 dB 100 100 dB 90 dB 80 80 dB 60 70 dB 60 dB 40 50 dB 40 dB 20 30 dB 20 dB 10 dB 0 Threshold of Hearing 20 31.5 63 125 250 500 1000 2000 4000 8000 16000 20000 Frequency (Hz) Figure 3.4: Response of human ears for various sound levels: Fletcher- Munson curves. Outer Ear Tube closed at one End Figure 3.5: Outer ear approximated by a tube closed at one end.
  • 144. CHAPTER 3. DECIBELS 66 Aux Audio dB Signal Receiver Generator Sound Level Speaker Meter (dB Meter) Figure 3.6: Measuring the frequency response of a speaker. Sound Level (dB) 90 Ideal 70 Real Frequency 20 Hz 1,000 Hz 20,000 Hz Figure 3.7: Frequency response of a speaker.
  • 145. Chapter 4 Loudspeakers 67
  • 146. CHAPTER 4. LOUDSPEAKERS 68 Electrical Signal Sound Input Output Loudspeaker Figure 4.1: Role of loudspeaker.
  • 147. CHAPTER 4. LOUDSPEAKERS 69 Amplitude Spectrum of an Input Tone Frequency + 1 2 3 4 5 6 7 Harmonics Frequency Response of Speaker Amplitude Frequency Resultant Sound from Speaker Amplitude Frequency 1 2 3 4 5 6 7 Harmonics Figure 4.2: Distortion of spectrum of original waveform by non- at fre- quency response of speaker.
  • 148. CHAPTER 4. LOUDSPEAKERS 70 High Frequencies Low Frequencies Figure 4.3: Dispersion properties of speakers.
  • 149. CHAPTER 4. LOUDSPEAKERS 71 2 O 1 Figure 4.4: Two low frequency waves from speaker arriving at O.
  • 150. CHAPTER 4. LOUDSPEAKERS 72 2 O 1 Figure 4.5: Two high frequency waves from speaker arriving at O.
  • 151. CHAPTER 4. LOUDSPEAKERS 73 2 1/2 W aves 2 O 1 Figure 4.6: Details of waves 2 and 1 at high frequencies.
  • 152. CHAPTER 4. LOUDSPEAKERS 74 "On Axis" All Frequencies are heard. Highs Speaker Middles Lows "Off Axis" High Frequencies are almost not heard. Figure 4.7: Sound dispersion of a driver as the frequency is increased.
  • 153. CHAPTER 4. LOUDSPEAKERS 75 Total Sound Output Woofer Frequency Total Sound Output Midrange Frequency Total Sound Output Tweeter Frequency Cross-over Frequencies Figure 4.8: Division of audio spectrum for a three-way loudspeaker.
  • 154. CHAPTER 4. LOUDSPEAKERS 76 3-Way Speaker Woofer Midrange Tweeter Total Sound Output 500 Hz 5000 Hz Frequency Figure 4.9: Net e ect of subdividing the whole audio range into three sec- tions. Woofer Tweeter Sound Output Frequency Cross-over Frequency Figure 4.10: Subdivision of audio spectrum in a two-way system.
  • 155. CHAPTER 4. LOUDSPEAKERS 77 Displacement Displacement A B Figure 4.11: Amount of sound produced depends on volume displacement. A is louder than B.
  • 156. CHAPTER 4. LOUDSPEAKERS 78 Displacement Displacement Figure 4.12: To produce same amount of sound by both drivers at the same frequency, the small one has to move through a larger distance than the big one.
  • 157. CHAPTER 4. LOUDSPEAKERS 79 Volume of Air moved (cm 3) 500 0.5 0.0005 Frequency 20 200 2000 20,000 Figure 4.13: Volume of air moved by loudspeaker as a function of frequency to produce same loudness of sound.
  • 158. CHAPTER 4. LOUDSPEAKERS 80 High Frequency Low Frequency Figure 4.14: Low frequency and high frequency simple pendulums doing di erent amounts of work per second for same amplitude of displacement. Sound Electrical Power and Power Heat In Dissipation IN OUT Figure 4.15: Balance between electrical power going to driver and the pro- duction of sound power and heat dissipation by driver.
  • 159. CHAPTER 4. LOUDSPEAKERS 81 Electrical Power Sound Input from Output Receiver (2 Watts) (80 Watts) Loudspeaker Figure 4.16: Example of a loudspeaker whose eciency is less than 100%.
  • 160. CHAPTER 4. LOUDSPEAKERS 82 Basket Suspension Spider Magnet Cone Voice Coil Figure 4.17: Basic cone speaker.
  • 161. CHAPTER 4. LOUDSPEAKERS 83 Cone-shaped Diaphragm Flat Diaphragm Figure 4.18: Comparison of cone-shape over at shape for mechanical strength when thin material is used.
  • 162. CHAPTER 4. LOUDSPEAKERS 84 Flexible Edge Diaphragm Figure 4.19: Modeling of diaphragm action by mass-spring oscillating sys- tem.
  • 163. CHAPTER 4. LOUDSPEAKERS 85 1 1 2 2 3 3 Side View Front View Figure 4.20: Standing wave on diaphragm of driver. N N A A A A Up Down Down Up N N N N Down Up Up Down A A A A N N = Node N A = Antinode Figure 4.21: Standing wave around rim of diaphragm.
  • 164. CHAPTER 4. LOUDSPEAKERS 86 Main Resonance Standing Wave Resonances Sound Pressure (dB) Frequency Figure 4.22: Typical frequency response of a cone speaker. Rear Sound (Out of Phase) Front Sound (In Phase) Rear Sound (Out of Phase) Figure 4.23: Bae problem in cone driver.
  • 165. CHAPTER 4. LOUDSPEAKERS 87 Figure 4.24: Front and rear of cone speakers are 180  out of phase.
  • 166. CHAPTER 4. LOUDSPEAKERS 88 Path = 1/2 Wave Baffle Figure 4.25: Bae action. Figure 4.26: Two possible approaches for trapping rear sound in a speaker by means of an enclosure.
  • 167. CHAPTER 4. LOUDSPEAKERS 89 Without Enclosure With Enclosure Amplitude Frequency Resonant Frequency of Driver + Enclosure Resonant Frequency of Driver OR Without Enclosure With Enclosure Amplitude Frequency Resonant Frequency of Driver + Enclosure Resonant Frequency of Driver Figure 4.27: E ect of enclosure on frequency response of speaker.
  • 168. CHAPTER 4. LOUDSPEAKERS 90 Cotton Wool Figure 4.28: Reducing standing waves inside speaker enclosure.
  • 169. CHAPTER 4. LOUDSPEAKERS 91 Driver Port Figure 4.29: Basic bass-re ex enclosure.
  • 170. CHAPTER 4. LOUDSPEAKERS 92 Figure 4.30: Oscillating components of bass-re ex speaker.
  • 171. CHAPTER 4. LOUDSPEAKERS 93 Amplitude Driver + Frequency Amplitude Enclosure Frequency Result Resultant Amplitude Frequency Figure 4.31: Splitting of original resonance into two new resonances in bass- re ex system.
  • 172. CHAPTER 4. LOUDSPEAKERS 94 Air in Enclosure Driver Air in Enclosure In-Phase Motion Air in Enclosure Air in Enclosure Out-of-Phase Motion Air in Enclosure Figure 4.32: Resonant behavior, in-phase and out-of-phase, motion of strongly coupled components of bass-re ex system.
  • 173. CHAPTER 4. LOUDSPEAKERS 95 Driver Air in Port Enclosure Figure 4.33: Coupled components of a bass-re ex speaker.
  • 174. CHAPTER 4. LOUDSPEAKERS 96 Driver Passive Radiator Figure 4.34: Bass-re ex speaker using a passive radiator over the port.
  • 175. CHAPTER 4. LOUDSPEAKERS 97 Mass Spring Figure 4.35: Helmholtz resonator behaves like mass-spring system.
  • 176. CHAPTER 4. LOUDSPEAKERS 98 Port Duct Figure 4.36: Bass-re ex speaker using a port or a duct.
  • 177. CHAPTER 4. LOUDSPEAKERS 99 Figure 4.37: Acoustic labyrinth enclosure.
  • 178. CHAPTER 4. LOUDSPEAKERS 100 Driver alone Driver + Small Enclosure Amplitude Frequency Very Low Resonant Frequency Figure 4.38: Change of frequency response of speaker when a small enclosure is used.
  • 179. CHAPTER 4. LOUDSPEAKERS 101 Amplitude Driver alone Frequency 15 Hz Large Compliance + = Small Enlosure Driver + Small Enclosure Amplitude Frequency 30 Hz Figure 4.39: E ect of small enclosure on frequency response of driver.
  • 180. CHAPTER 4. LOUDSPEAKERS 102 Figure 4.40: Transfer of energy from a bob to one of equal mass, and to one of di erent mass.
  • 181. CHAPTER 4. LOUDSPEAKERS 103 Diaphragm Air Mouth Chamber Throat Figure 4.41: A horn for matching vibrations of a light diaphragm to a large volume of air. Amplitude Frequency Cut-off Frequency Figure 4.42: Low frequency response of a horn.
  • 182. CHAPTER 4. LOUDSPEAKERS 104 Conical Parabolic Exponential Hyperbolic Figure 4.43: Some common horn shapes.
  • 183. CHAPTER 4. LOUDSPEAKERS 105 Diaphragm Figure 4.44: Folded horn.
  • 184. CHAPTER 4. LOUDSPEAKERS 106 Figure 4.45: Two-way horn loudspeaker with bass-re ex enclosure.
  • 185. CHAPTER 4. LOUDSPEAKERS 107 1/2 Wavelength Loudspeaker Figure 4.46: Standing wave set up in a room with maxima and minima in sound pressure. Loudspeaker Direct Figure 4.47: Re ected waves by a wall appear to come from behind the wall since it acts like a mirror.
  • 186. CHAPTER 4. LOUDSPEAKERS 108 Lows Middles Middles Highs Highs Lows Lows Figure 4.48: Stereo coverage in a room. + + _ L _ + R _ + _ Figure 4.49: Speaker phasing: speakers are in phase.
  • 187. CHAPTER 4. LOUDSPEAKERS 109 + + _ L _ + R _ _ + Figure 4.50: Speaker phasing: speakers are out of phase. Wall Reflected Reflected Direct Figure 4.51: Geometry of a Bose 901 speaker.
  • 188. CHAPTER 4. LOUDSPEAKERS 110 Speaker Amplitude Frequency Amplitude Equalizer Frequency Speaker Resultant Amplitude Frequency Figure 4.52: E ect of equalizer on frequency response of Bose speakers.
  • 189. CHAPTER 4. LOUDSPEAKERS 111 Wall Figure 4.53: Bass horn in Klipsch horn speaker. Left Channel +12 dB 0 dB -12 dB 62Hz 250Hz 1kHz 4kHz 8kHz Figure 4.54: Graphic equalizer.
  • 190. Chapter 5 Electricity 112
  • 191. CHAPTER 5. ELECTRICITY 113 Electron N Proton N Neutron Electron Figure 5.1: Example of an atom: a Helium atom.
  • 192. CHAPTER 5. ELECTRICITY 114 Figure 5.2: Forces between charged objects; like charges repel and unlike charges attract.
  • 193. CHAPTER 5. ELECTRICITY 115 Figure 5.3: Charged ping-pong balls repelling each other. Figure 5.4: Electric
  • 194. eld produced by a charged object.
  • 195. CHAPTER 5. ELECTRICITY 116 Figure 5.5: Electric
  • 196. eld between two charged plates. Output Left Right Battery Receiver Figure 5.6: Examples of voltage sources: a battery, the output of a receiver.
  • 197. CHAPTER 5. ELECTRICITY 117 Plates Sheet Figure 5.7: Electrostatic speaker: basic principle and actual speaker. Plates Sheet Figure 5.8: Simpli
  • 198. ed version of an electrostatic speaker at equilibrium.
  • 199. CHAPTER 5. ELECTRICITY 118 Figure 5.9: Push-pull action by two plates on charged sheet. Spacers Diaphragm (Vibrating Sheet) Plates Figure 5.10: An electrostatic speaker.
  • 200. CHAPTER 5. ELECTRICITY 119 Stress Si Ion O2 Ion Quartz Stress Figure 5.11: Some crystals under pressure produce positive and negative charges on surface. V=0 V V Figure 5.12: Dimensional changes of a piezoelectric ceramic when a voltage is applied.
  • 201. CHAPTER 5. ELECTRICITY 120 V V Figure 5.13: Bending action of a double piezoelectric driver. Bimorph Cone Figure 5.14: Pumping action of cone caused by bending of bimorph.
  • 202. CHAPTER 5. ELECTRICITY 121 Diaphragm Figure 5.15: Typical piezo horn. Wire Figure 5.16: Wire connected between two charged objects allows charges to be transferred.
  • 203. CHAPTER 5. ELECTRICITY 122 + L _ + R _ Figure 5.17: Flow of electric current from ampli
  • 204. er to speaker. Atom Bound Electrons Figure 5.18: Solid with atoms where electrons are tightly bound and which does not conduct electricity under normal circumstances.
  • 205. CHAPTER 5. ELECTRICITY 123 Electron Figure 5.19: Motion of one electron in a conductor in the presence of an electric
  • 206. eld. Changes of direction are due to scattering.
  • 207. CHAPTER 5. ELECTRICITY 124 Metal Electrical Resistance Temperature (˚K) 0 100 200 300 Figure 5.20: Temperature dependence of the electrical resistance in a con- ductor. Superconductor Electrical Resistance Temperature (˚K) 0 100 200 300 Tc Figure 5.21: Superconductivity at Tc below which the resistance is zero.
  • 208. CHAPTER 5. ELECTRICITY 125 1 Wire of Conductor 2 1 Water flowing in Pipe 2 Figure 5.22: The resistance to current or to water ow increases as the length of a conductor or pipe increases. Resistance of 2 is double that of 1. Wire of Conductor Water flowing in Pipe Figure 5.23: By increasing the cross-sectional area of a conductor, resistance to current or water ow decreases.
  • 209. CHAPTER 5. ELECTRICITY 126 Figure 5.24: Resistor with colored bands to specify its resistance value. Extra Missing Bonding Electron Electron = Hole Si Si Si Si Si Si Si Si Si Si Si Si Si As Si Si Ga Si Si Si Si Si Si Si Si Si Si Figure 5.25: Pure silicon, silicon doped with arsenic, and silicon doped with gallium. + Voltage Resistance Amplifier Source _ Simple Model Figure 5.26: Example of simple circuit.
  • 210. CHAPTER 5. ELECTRICITY 127 Water Flow Pump Resistance to Water Flow Figure 5.27: Model using water for electric circuit.
  • 211. CHAPTER 5. ELECTRICITY 128 DC Current Time AC Current Time Figure 5.28: Comparison between DC and AC current. Pressure Sound Voltage AC Signal Time Time Figure 5.29: Representation of a sound wave by an AC electrical signal.
  • 212. CHAPTER 5. ELECTRICITY 129 Y X Z Figure 5.30: Variable resistance between X and Y. Fine Wire Voltage Fuse Source Figure 5.31: Fuse to protect speaker. Speaker 1 Speaker 2 + L _ + R _ Figure 5.32: Two speakers connected in series to one channel of ampli
  • 213. er.
  • 214. CHAPTER 5. ELECTRICITY 130 Speaker 1 Speaker 2 Voltage Effective Resistor Source Figure 5.33: Model of series circuit. + L _ + R _ Figure 5.34: Parallel connection of two speakers to an ampli
  • 215. er.
  • 216. CHAPTER 5. ELECTRICITY 131 Speaker 1 Speaker 2 Voltage Effective Resistor Source Figure 5.35: Model of parallel connections. House Outlet CD Etc. Receiver Equalizer 120 V Player 60 Hz Figure 5.36: Parallel connections of hi-
  • 217. components to house electrical outlet.
  • 218. CHAPTER 5. ELECTRICITY 132 Mass • Mass of Cone • Compliance of Suspension • Friction Suspension Figure 5.37: Response of cone speaker to a force.
  • 219. CHAPTER 5. ELECTRICITY 133 Figure 5.38: Coil used to produce a magnetic
  • 220. eld when a current ows through it. It has inductance.
  • 221. CHAPTER 5. ELECTRICITY 134 Impedance due to Inductance Frequency 20 Hz 20,000 Hz Figure 5.39: Frequency dependence of impedance associated with induc- tance. Voltage Voltage Source Source Figure 5.40: Charging of a capacitor.
  • 222. CHAPTER 5. ELECTRICITY 135 Voltage Voltage Source Source Figure 5.41: Charging of a capacitor when polarity of voltage source is reversed. Impedance due to Capacitance Frequency 20 Hz 20,000 Hz Figure 5.42: Frequency dependence of impedance due to capacitance.
  • 223. CHAPTER 5. ELECTRICITY 136 Inductance Sound Output In from Amplifier Woofer Woofer Frequency Figure 5.43: Inductance in series with woofer prevents high frequencies from reaching it. Capacitance Sound Output In from Amplifier Tweeter Tweeter Frequency Figure 5.44: Capacitance in series with tweeter. It prevents low frequencies from reaching it.
  • 224. CHAPTER 5. ELECTRICITY 137 In from Amplifier Mid-range Sound Output Mid-range Frequency Figure 5.45: Capacitance and inductance in series with mid-range speaker to prevent the high and low frequencies from reaching it. Impedance Frequency Resonant Frequency Figure 5.46: Impedance curve of driver.
  • 225. Chapter 6 Ampli
  • 226. ers 138
  • 227. CHAPTER 6. AMPLIFIERS 139 Sources of Audio Signals Amplifier (CD, Tape, etc.) Weak Large Signals Signals Figure 6.1: Importance of ampli
  • 228. er in hi-
  • 229. system. Source Command from Audio Signals Sound Output Power Supply Figure 6.2: Basic ampli
  • 230. er.
  • 231. CHAPTER 6. AMPLIFIERS 140 Source Command: More Current Sound Output Power Supply Figure 6.3: Ampli
  • 232. er command for more current. Source Command: Less Current Sound Output Power Supply Figure 6.4: Ampli
  • 233. er command for less current.
  • 234. CHAPTER 6. AMPLIFIERS 141 Holes Electrons p-Type n-Type Figure 6.5: Semiconductor junction. No Current flow p-type n-type p-type n-type Battery Battery Figure 6.6: Reverse-biased semiconductor junction.
  • 235. CHAPTER 6. AMPLIFIERS 142 Current flows p-type n-type p-type n-type Battery Battery Figure 6.7: Forward-biased semiconductor junction. Current -Voltage +Voltage Figure 6.8: Symbol for diodes and its characteristics. Diode Input Voltage Voltage across Resistor Figure 6.9: Recti
  • 236. er action of a diode when an AC voltage is applied.
  • 237. CHAPTER 6. AMPLIFIERS 143 n p n p n p Emitter Collector Emitter Collector Base Base Figure 6.10: Diagram of transistor and its circuit symbol for two possibilities. Water Tank Current Flow Command goes in as Current Control (Control) Power Supply Water Flow Figure 6.11: Ampli
  • 238. er action of transistor in a circuit compared to control of water ow.
  • 239. CHAPTER 6. AMPLIFIERS 144 Signal Out Signal In Amplifier Figure 6.12: Function of an ampli
  • 240. er. + Battery Inverting Input Amplifier Output Non-Inverting Input - Battery Ground Figure 6.13: Ampli
  • 241. er integrated on a chip. Rf Input Amplifier Output R input Figure 6.14: Operational ampli
  • 242. er with negative feedback.
  • 243. CHAPTER 6. AMPLIFIERS 145 Rf Input Amplifier Output R input Figure 6.15: Negative feedback corrects uctuations in gain. Microphone Speaker Amplifier Figure 6.16: Positive feedback in large hall with a mike and a loudspeaker system driven by mike.
  • 244. CHAPTER 6. AMPLIFIERS 146 Input Output Ground Figure 6.17: Volume control. Input Output is Ball at Maximum Voltage Maximum Energy due to its Position Ground Input Ball at Minimum Energy Output is due to its Minimum Voltage Position Ground Figure 6.18: Comparison of potentiometer action with energy of a ball on a ladder.
  • 245. CHAPTER 6. AMPLIFIERS 147 Bass Treble Min Max Min Max Figure 6.19: Bass and Treble controls.
  • 246. CHAPTER 6. AMPLIFIERS 148 Max. bass Max. Treble + 13 Middle Position Relative Output Frequency (dB) 20 Hz 20,000 Hz 1000 Hz -13 Min. Bass Min. Treble Figure 6.20: E ect on signal spectrum of Bass and Treble controls. Low, 6 dB/Octave High, 6 dB/Octave Relative Ideal Case Amplitude with no Filter (dB) Low, 18 dB/Octave High, 18 dB/Octave Frequency 20 Hz 20,000 Hz Figure 6.21: Action of LOW and HIGH
  • 247. lters with 6 dB/octave attenuation, and also with 18 db/octave attenuation.
  • 248. CHAPTER 6. AMPLIFIERS 149 Signal Out Signal In Amplifier f Extra Harmonics + + + ... = 2f 3f f Signal Out Figure 6.22: Harmonic distortion by ampli
  • 249. er. Non-linear Output Linear Input Figure 6.23: Non-linear gain of ampli
  • 250. er.
  • 251. CHAPTER 6. AMPLIFIERS 150 Signal Out Signal In f1 Frequency f1 f2 Frequency f2 Amplifier f1- f2 f1+ f2 Figure 6.24: IM distortion in ampli
  • 252. er. IM Distortion THD (%) Power Output Power Rating of Amplifier Figure 6.25: Distortion increases sharply about power rating of ampli
  • 253. er.
  • 254. CHAPTER 6. AMPLIFIERS 151 Signal Out Signal In Amplifier Large THD due to Clipping Figure 6.26: Clipping of waveform by ampli
  • 255. er at high output levels beyond the rated value. Signal Out Signal In Amplifier Noise Figure 6.27: E ect of noise from ampli
  • 256. er.
  • 257. CHAPTER 6. AMPLIFIERS 152 A Relative Output (dB) Frequency 20 Hz 20,000 Hz B Relative Output (dB) Frequency 20 Hz 20,000 Hz Figure 6.28: Comparing 2 ampli
  • 258. ers with the same specs. Even though their specs are the same, the ampli
  • 259. ers will sound di erent. 0 dB Noise Level A - weighted Measured Noise Level Frequency 20 Hz 20,000 Hz Figure 6.29: A-weighted method of measuring noise.
  • 260. Chapter 7 Electromagnetism 153
  • 261. CHAPTER 7. ELECTROMAGNETISM 154 Current Figure 7.1: E ect of current in a wire on compasses around it. North South Figure 7.2: Bar magnet has a north pole and a south pole. North South N S N S Figure 7.3: Cutting a bar magnet produces shorter magnets each with its own respective north and south poles.
  • 262. CHAPTER 7. ELECTROMAGNETISM 155 Current N S N S Magnetic Field Magnetic Field Figure 7.4: Magnetic dipole is the basic unit of magnetism. Magnetic Domain Iron Atom Figure 7.5: Unmagnetized piece of iron.
  • 263. CHAPTER 7. ELECTROMAGNETISM 156 North South N S Magnet Magnetized Iron Figure 7.6: Alignment of domains in a piece of iron by a bar magnet. Iron becomes magnetized. Current North South Figure 7.7: Magnetic
  • 264. eld around a bar magnet and a wire carrying a cur- rent.
  • 265. CHAPTER 7. ELECTROMAGNETISM 157 Battery Many Loops = Coil Single Loop Figure 7.8: Increasing the magnetic
  • 266. eld produced by a current in a wire: by forming a loop, and by using many loops. S N - + Power Supply Figure 7.9: An electromagnet.
  • 267. CHAPTER 7. ELECTROMAGNETISM 158 S N - + Power Supply Figure 7.10: Determination of direction of magnetic
  • 268. eld using
  • 269. rst left-hand rule. Current S N North Pole - + Left Hand Figure 7.11: Rule for determining direction of magnetic
  • 270. eld in an electro- magnet.
  • 271. CHAPTER 7. ELECTROMAGNETISM 159 Direction of Motion Fixed Magnet N S N S Amplifier Figure 7.12: First left-hand rule and how a cone speaker works. Force Current N S Figure 7.13: Force on wire carrying a current in a magnetic
  • 272. eld.
  • 273. CHAPTER 7. ELECTROMAGNETISM 160 Force Current (Negative to Positive) Magnetic Field (North to South) Left Hand Figure 7.14: The second left-hand rule showing direction of force on wire carrying a current in a magnetic
  • 274. eld.
  • 275. CHAPTER 7. ELECTROMAGNETISM 161 Current Magnetic Field Magnetic Field Current Zero Force Maximum Force Figure 7.15: Direction of force depends on orientation of current with respect to magnetic
  • 276. eld.
  • 277. CHAPTER 7. ELECTROMAGNETISM 162 Magnet Poles S S S + N N N Magnet Poles Figure 7.16: A Heil Speaker.
  • 278. CHAPTER 7. ELECTROMAGNETISM 163 Magnet Pole S Force Force Wire with Current N Magnet Pole Figure 7.17: One set of folds in Heil speaker.
  • 279. CHAPTER 7. ELECTROMAGNETISM 164 Wire Sheet S N S N Magnet N S + N S N S Figure 7.18: Magnetic Planar Speaker.
  • 280. CHAPTER 7. ELECTROMAGNETISM 165 S N S N Wire S N S N Figure 7.19: Forces on diaphragm when current direction is as indicated. N S Figure 7.20: A bar magnet moving into a coil induces an electric current in that coil.
  • 281. CHAPTER 7. ELECTROMAGNETISM 166 N S N S N S Figure 7.21: Induced current in coil by moving magnet.
  • 282. CHAPTER 7. ELECTROMAGNETISM 167 N S N S Figure 7.22: Signi
  • 283. cance of relative motion between magnet and coil. WRONG!! N S Figure 7.23: Direction of induced current (wrong).
  • 284. CHAPTER 7. ELECTROMAGNETISM 168 CORRECT!! N S Figure 7.24: Direction of induced current (correct).
  • 285. CHAPTER 7. ELECTROMAGNETISM 169 Primary Coil Secondary Coil Core Figure 7.25: Schematic of a transformer and its circuit symbol.
  • 286. CHAPTER 7. ELECTROMAGNETISM 170 Primary Coil Secondary Coil Figure 7.26: Step-up transformer. Primary Coil Secondary Coil Figure 7.27: Step-down transformer.
  • 287. CHAPTER 7. ELECTROMAGNETISM 171 N S Figure 7.28: Schematic of microphone based on Faraday's law of induction. S N Figure 7.29: Exercise 7.14.
  • 288. CHAPTER 7. ELECTROMAGNETISM 172 S N Stationary + Figure 7.30: Exercise 7.15. N S Figure 7.31: Exercise 7.18.
  • 289. Chapter 8 Electromagnetic Waves and Tuners 173
  • 290. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 174 Figure 8.1: Electric Field around charged ping-pong ball. Figure 8.2: Oscillating charged ball.
  • 291. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 175 High-frequency Oscillating Charged Comb Oscillating Electron Figure 8.3: Generation of electromagnetic waves at two di erent frequencies. Radio Microwave Infrared Light Ultra-violet X-rays Gamma-rays 6 10 Hz 10 8 Hz 10 12 Hz 10 14 Hz 10 15 Hz 10 16 Hz 10 18 Hz Figure 8.4: Spectrum of electromagnetic waves.
  • 292. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 176 Electric Field Magnetic Field Direction of Travel Figure 8.5: Electromagnetic waves are transverse waves with oscillating elec- tric and magnetic
  • 293. elds. e- e- Waveform Waveform e- e- Voltage Voltage Source Source Antenna Antenna Figure 8.6: Production of electromagnetic waves by oscillating electrons in antenna.
  • 294. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 177 Electric Magnetic Field Field Figure 8.7: Generation of electric and magnetic
  • 295. elds by antenna. Antenna Broadcasted Wave Figure 8.8: Production of electromagnetic waves by antenna.
  • 296. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 178 Modulation: Pressure Increase Ambient Pressure Test Writing Pressure Decrease Painting a Picture Sound Figure 8.9: Some examples of modulation. Audio Signal Amplitude Modulated Carrier Carrier Wave Figure 8.10: Amplitude modulation.
  • 297. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 179 Station 1,000 kHz Modulated Carrier Wave Carrier Audio Signal Station 1,400 kHz Modulated Carrier Wave Carrier Audio Signal Figure 8.11: Carrier and audio signals broadcast by two stations. Amplitude Carrier Frequency f - Audio f f + Audio Frequency Frequency Figure 8.12: Spectrum of an AM carrier at frequency f when modulated by audio signal.
  • 298. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 180 AM Waves Amplitude Carrier f Frequency Figure 8.13: Audio frequencies modulating carrier. Sideband Frequencies Relative Carrier Amplitude Frequency f - 5 kHz f f + 5 kHz Figure 8.14: Spectrum of frequencies on carrier for audio frequencies up to 5 kHz.
  • 299. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 181 1 Station Next Station Relative Amplitude Carrier 1 Carrier 2 995 kHz 1000 kHz 1005 kHz Frequency Figure 8.15: Spectrum of frequencies due to modulation of carrier. Carrier Signal Audio Signal Amplitude does not change Frequency changes Frequency Modulated Carrier Wave Figure 8.16: Frequency modulation (FM).
  • 300. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 182 Low Frequency Audio High Frequency Audio Carrier Carrier Figure 8.17: A low frequency and a high frequency audio signal frequency modulating a carrier.
  • 301. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 183 Quiet Audio Carrier Loud Audio Carrier Figure 8.18: A loud and a quiet audio signal frequency modulating a carrier.
  • 302. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 184 Spikes Limiter Figure 8.19: Action of limiter in FM. Audio Information 17 Relative Amplitude (dB) 0 Frequency 20 Hz 1 kHz 15 kHz Figure 8.20: Pre-emphasis in FM broadcasting.
  • 303. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 185 Audio Information 17 Relative Amplitude Noise picked up (dB) in Atmosphere 0 Frequency 20 Hz 1 kHz 15 kHz Figure 8.21: Information brought to tuner on carrier. Audio Information 0 Relative Amplitude (dB) Noise -17 Frequency 20 Hz 1 kHz 15 kHz Figure 8.22: De-emphasis of audio information to reduce high frequency noise.
  • 304. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 186 Antenna Antenna Transmitter Tuner Amp In Out Figure 8.23: Elements of radio communications. rf IF Rectifier Mixer and Amplifier Amplifier Filter Out Local Oscillator Figure 8.24: Superheterodyne receiver. I-F Signal A-F Signal Rectifier Filter Figure 8.25: Processing part of AM signal with a simple diode and
  • 305. lters.
  • 306. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 187 Amplitude Pilot Frequency L+R L-R L-R Frequency 50 15,000 19,000 23,000 38,000 53,000 Hz Figure 8.26: Audio information which will modulate carrier in stereo broad- casting.
  • 307. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 188 Antenna Electric Field At the same time ... Magnetic Field Figure 8.27: Alternating current in antenna produces electromagnetic wave.
  • 308. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 189 Electric Field Electric Field Capacitor Plates Antenna Wires Figure 8.28: Electric
  • 309. eld around charged antenna wires is similar to that between charged capacitor plates. Current Current Magnetic Field Wire with Current Current Antenna with Current Figure 8.29: Magnetic
  • 310. elds around a wire and antenna with current.
  • 311. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 190 Incident Current Wave Reflected Current Wave Resultant Wave Current Figure 8.30: Development of a standing wave on antenna.
  • 312. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 191 Current Standing Wave on an Antenna Displacement Standing Wave on a String Figure 8.31: Comparison of standing wave on antenna to that of a string.
  • 313. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 192 Antenna Axis Figure 8.32: Radiation pattern of electric
  • 314. eld around half-wave dipole an- tenna. 270˚ 0˚ 180˚ Antenna Radiation Lobe 90˚ Figure 8.33: Polar graph representation of radiation pattern around half- wave dipolar antenna.
  • 315. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 193 Antenna 1/4 Wave 1/4 Wave Current Co-axial Cable to Electronics 1/4 Wave Reflection Earth Electric Earth Conductor Figure 8.34: Basic elements of a grounded vertical antenna. 1/4 Wave Ground Plane Figure 8.35: Quarter-wave antenna.
  • 316. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 194 Reflected Part Earth Figure 8.36: Total antenna length is made shorter by inserting a coil in series.
  • 317. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 195 Electric Field of Radio Wave Receiving Antenna Figure 8.37: When the electric
  • 318. eld of radio wave is vertical, the receiving antenna should also be vertical. Loop Antenna Magnetic Field of Radio Wave Tuner Figure 8.38: Loop antenna detects the magnetic
  • 319. eld part of radio wave.
  • 320. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 196 Magnetic Core (Ferrite) Loop Antenna Loop Antenna with many turns with many turns and Ferrite Core Figure 8.39: Two common loop antennas. Broadcast Vertical Polarization Antenna Electric Field Earth Receiving Antenna Figure 8.40: Vertically polarized radio wave.
  • 321. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 197 Broadcast Antenna Horizontal Polarization Earth Receiving Electric Field Antenna Figure 8.41: Horizontally polarized radio wave. 2 Mutually Perpendicular Antennas Circularly Polarized Wave Figure 8.42: Broadcasting with circular polarization.
  • 322. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 198 Broadcast Antenna Ground Wave Earth Figure 8.43: Low frequency ground wave follows curvature of earth. Broadcast Antenna Straight Line Path Earth Figure 8.44: Direct (line-of-sight) mode of propagation.
  • 323. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 199 F1 F2 150 Miles 300 Miles Ionosphere 70 miles D 30 Miles 50 Miles Earth Figure 8.45: Earth's ionosphere layers. Ionosphere Reflected Broadcast Sky Antenna Wave Earth Figure 8.46: Sky wave world communications.
  • 324. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 200 Ionosphere Broadcast Antenna Earth Figure 8.47: Two-hop transmission of radio wave using ionosphere. Earth Geostationary Satellite Figure 8.48: Communication using a satellite.
  • 325. CHAPTER 8. ELECTROMAGNETIC WAVES AND TUNERS 201 99.6 100 100.4 MHz Dial on Tuner 99.8 100.2 Figure 8.49: Selectivity relates to how well alternate channels are rejected. Reflected Broadcast Antenna Receiver Direct Figure 8.50: Direct and re ected waves from a broadcasting station. 100 Mhz 100 Mhz Receiver Should be suppressed Figure 8.51: Capture ratio in tuner.
  • 326. Chapter 9 Analog Recording and Playback 202
  • 327. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 203 Top View Left Right Channel Channel Side View Figure 9.1: Record with grooves representing mechanically engraved waves.
  • 328. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 204 Output Piezoelectric Element Piezoelectric Pick-up Magnet SN Moving Magnet Pick-up Figure 9.2: Phono playback systems.
  • 329. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 205 Left Right 90˚ Figure 9.3: Stereo with only one stylus.
  • 330. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 206 SN Figure 9.4: A stereo moving magnet phono cartridge. Magnetic Domain Unmagnetized Magnetic Material Magnetized Magnetic Material Magnetization is Zero Magnetization is Non-Zero Figure 9.5: Unmagnetized and magnetized magnetic material.
  • 331. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 207 Magnetic Field Current Magnetic Field in Coil Current in Coil Figure 9.6: Magnetic
  • 332. eld produced by a coil when current ows through it.
  • 333. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 208 Total Magnetization Saturation Current in Coil Figure 9.7: Alignment of domains in a magnetic material.
  • 334. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 209 Total Magnetization Saturation Rententivity Current in Coil Figure 9.8: Behavior of magnetic material in a coil whose current is increased and decreased to zero.
  • 335. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 210 Magnetization Current in Coil Coercivity Current in Coil Figure 9.9: Memory is destroyed by reversed current in coil.
  • 336. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 211 Magnetization Magnetic Field of Coil Magnetic Field of Coil Magnetization Figure 9.10: Hysteresis curve of magnetic material.
  • 337. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 212 Hard Soft Figure 9.11: Groups of magnetic materials.
  • 338. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 213 Side View Magnetic Particles Polyester Film Stereo L1 1 R1 2 L2 3 Heads R2 4 Top View Figure 9.12: Side and top views of magnetic tape. Figure 9.13: Magnetic particle of gamma { Iron (III) Oxide as used on tapes.
  • 339. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 214 Audio Input N S S N N S Tape Motion Figure 9.14: Recording head aligning magnetic domains on tape.
  • 340. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 215 Audio Signal: Top View of Tape Domain Domain Alignment Alignment N S S N 1 Wave Audio Signal: Top View of Tape 1 Wave Figure 9.15: Analog recording on a magnetic tape.
  • 341. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 216 N S S N N S S N 1 Wave 1 Wave High Frequency Low Frequency Figure 9.16: Recorded information on magnetic tape. Output S N N S Tape Motion Gap (Exaggerated) Figure 9.17: Playback head for reading information on a tape. Output S N N S 1 Wave Tape Motion Figure 9.18: Playback head reading signals.
  • 342. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 217 Erase Record Playback Tape Figure 9.19: Order of heads on a tape deck. Magnetization Recording Recording Current Current in Coil in Coil Magnetization Figure 9.20: Recording on material with magnetic hysteresis.
  • 343. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 218 Magnetization Recorded Information Recording Current in Coil Input Current to Coil Figure 9.21: Recording a signal on a tape.
  • 344. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 219 Magnetization Recorded Information Current in Input Coil Input Information Linear Characteristic of Tape Figure 9.22: Ideal magnetic characteristics for tape | linear behavior.
  • 345. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 220 Magnetization Region to be avoided Current in Coil Almost Linear Regions Figure 9.23: Useful region on hysteresis curve for magnetic recording.
  • 346. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 221 Audio Output 0 Audio + Bias on Tape + A-C Bias Input Audio Input Audio + Bias Input Figure 9.24: Recording on magnetic tape with bias.
  • 347. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 222 Audio Signal Recording Amplifier Bias Playback Oscillator Amplifier Erase Record Playback Figure 9.25: Details of heads for magnetic recording. Output from Playback Head Frequency 20 Hz 20,000 Hz Figure 9.26: Frequency dependence of output from playback head.
  • 348. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 223 Output from 1 µm Gap Playback Head 2 µm Gap 4 µm Gap Frequency 20 Hz 10 kHz 20 kHz Output from 15 i.p.s. Playback Head 71/2 i.p.s. 1 7/8 i.p.s. Frequency 20 Hz 10 kHz 20 kHz Figure 9.27: Output from playback head as a function of frequency for various gap sizes and tape speeds. Output 70 µ sec Equalization (dB) 120 µ sec Equalization Frequency 20 Hz 100 Hz 1000 Hz 10 kHz 20 kHz Figure 9.28: Equalization in playback.
  • 349. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 224 Output (dB) Frequency 20 Hz 5000 Hz 20 kHz Figure 9.29: Equalization in recording. Transients Amplitude Average Sound Levels Time Figure 9.30: Typical musical spectrum.
  • 350. CHAPTER 9. ANALOG RECORDING AND PLAYBACK 225 Recording Level (dB) 0 -10 -20 Frequency 10 Hz 1 kHz 10 kHz 20 kHz Figure 9.31: Frequency response at di erent recording levels. X Y Figure 9.32: Exercise 9.4.
  • 351. Chapter 10 Digital Optical Recording & Playback 226
  • 352. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 227 Pressure Voltage Time Time Continuous Representation Figure 10.1: Sound wave and its analog representation as a voltage.
  • 353. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 228 High Frequency Signal Scratch Groove Very Large Amplitude Signal Figure 10.2: Grooves on a record representing analog signals.
  • 354. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 229 Playback Tape Dirt Tape Motion Recorded Signal Played Back Signal Figure 10.3: Distortion of analog signal by dirt stuck between playback head and tape. 2 Original Number 2 Worn out Number 2 Figure 10.4: Original number 2 and worn out number 2; basic information is not lost when number is worn out.
  • 355. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 230 Amplitude Amplitude (Decimal) (Binary) 8 1000 4 0100 2 0010 0 0000 Time Time Figure 10.5: (a) Analog signal, decimal scale (b) Analog signal, binary scale. 20 Hz Time 200 Hz Time Figure 10.6: 20 Hz wave will get more samples per wave than a 200 Hz wave.
  • 356. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 231 Aliased Signal Signal Samples (not enough!) Signal No Aliasing Samples (good!) Figure 10.7: Aliasing due to inadequate sampling rate.
  • 357. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 232 Sampling Frequency Good, No Aliasing, F=F /2 S Maximum Signal Signal Frequency F = FS / 2 Frequency FS F+F /2 S S Poor, Aliasing, Maximum Signal Alias Zone Frequency F > FS / 2 Frequency FS F+F /2 S S F>F /2 S Figure 10.8: Audio spectrum and sideband frequencies due to sampling.
  • 358. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 233 Sample and Hold of Analog Signal Amplitude Holds Time Sampling Points Figure 10.9: Sample and hold of a signal for digitizing. In Left Out Multiplexer In Right 2 Channels 1 Channel Figure 10.10: Multiplexing of left and right channels.
  • 359. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 234 1000 0110 0111 0100 0101 0011 0011 0010 0010 0001 0001 Analog Signal Sampled Analog Signal Digital Signal Left Channel Low-Pass Sample & A/D Filter Converter Hold First Multiplexer Right Channel Low-Pass Sample A/D Filter & Converter Hold Figure 10.11: Digitizing a signal. Output from D/A Converter Figure 10.12: Output of D-A converter.
  • 360. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 235 Smoothing by Low-pass Filter Output from D/A Converter Figure 10.13: Output of low-pass
  • 361. lter. Left Channel Left Channel In Analog Out Low-Pass D/A Converter Filter Digital 0100 1000 1101 1001 Figure 10.14: Main features of playback of digital signal.
  • 362. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 236 Disc Travels Slower To keep constant Laser Beam to Disc Speed Disc Travels Faster Pits and Lands Figure 10.15: Details of information on a CD.
  • 363. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 237 Land 1/4 Wave Pit Laser Beam Out of Phase by 1/2 Wave Figure 10.16: Interference between light beam re ected from pit and from at. Pits Label Protective Layer Metal Film Layer Compact Disc Transparent Substrate Lens In Out Laser Beam Figure 10.17: Focusing action of a laser beam by lens.
  • 364. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 238 Dirt out of Focus Compact Disc Dirt Lens Laser Beam Figure 10.18: Reduced e ect of surface defect on CD.
  • 365. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 239 Land Length Pit Length Land Pit Track Pitch 1.6 µm Track Width 0.5 µm Laser Beam 0.8 µ m Figure 10.19: Laser spot focused on disc data.
  • 366. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 240 Laser Beam to Track Disc Direction Laser Beam to Read Laser Beam to Track Pit Figure 10.20: Three-beam detection; one for read-out and two beams for tracking.
  • 367. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 241 Wave Wave Randomly Polarized Plane Polarized Figure 10.21: Randomly polarized beam and plane-polarized beam.
  • 368. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 242 Compact Disc Objective Lens Circularly Polarized Light 1/4 Wave Plate Vertically Polarized Light To Detector Beam Splitter Out Cylindrical Lens Converging Lens Horizontally Polarized Light In from Laser Figure 10.22: Path of laser beam and role of its polarization.
  • 369. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 243 Coherent Beam of Light Incoherent Beam of Light Figure 10.23: Coherent and incoherent beams of light.
  • 370. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 244 Current Front Mirror Rear Mirror pn Junction Laser Beam Current Figure 10.24: Semiconductor laser.
  • 371. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 245 Sampled Signal 2 × Oversampled 4 × Oversampled Figure 10.25: E ect of 2-times and 4-times oversampling.
  • 372. CHAPTER 10. DIGITAL OPTICAL RECORDING & PLAYBACK 246 Mini Disc Optical Readout In: 1.4 MBit / Second Memory Out: 0.3 MBit / Second Figure 10.26: Shock-proof memory in mini-disc.
  • 373. Chapter 11 Digital Magnetic Recording & Playback 247
  • 374. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK248 Track Magnetic Domains Figure 11.1: Magnetic digital signals recorded vertically on a mini disc. Signal In Recording Protective Layer Magnetic Head Magnetic Recording Layer Mini Disc Substrate Lens Laser Beam Figure 11.2: Recording digital signals on a mini disc.
  • 375. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK249 S Magnet N Polarization Rotation of Polarization Plane Laser Beam In Reflected Figure 11.3: Kerr e ect: plane of polarization of light beam rotates upon re ection from a magnetized surface. Record Record Head Head In Out Lens Lens Polarization Plane Figure 11.4: Read-out of digital information using Kerr e ect. Magnetic
  • 376. eld direction a ects plane of polarization of re ected laser beam.
  • 377. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK250 Prerecorded Disc In Out Lens Lens Change in Intensity Interference Bright Less Bright Effect Recordable Disc In Out Lens Lens Change in Kerr Effect Polarization Plane Figure 11.5: Di erence in read-out between pre-recorded and recordable mini-discs.
  • 378. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK251 Pre-grooved for Tracking Laser Spot Pre-groove SiN SiN Reflective Layer Magneto-optic Layer Figure 11.6: Section of a recordable mini disc. Program Area Lead-in Area Lead-out Area Figure 11.7: Layered structure of recordable mini disc.
  • 379. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK252 Upper Sector Lower Sector Figure 11.8: Track pattern in DCC tape. DCC Head Record Read Record Playback 0 0 1 1 2 2 Upper 3 4 3 4 Sector 5 6 5 6 7 Digital 7 8 8 Right Analog Playback Left Only Figure 11.9: The playback head reads only a portion of the recorded track. SPL-dB Treshold of Hearing Frequency .02 .05 .1 .2 .5 1 2 5 10 20 kHz Figure 11.10: Threshold of hearing curve.
  • 380. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK253 SPL-dB Record New Treshold Ignore Frequency .02 .05 .1 .2 .5 1 2 5 10 20 kHz Figure 11.11: Sounds which will be recorded by PASC and masking of quiet passages. 1 1 0 Audio Signal: Tape Figure 11.12: Representation of digital signal on magnetic tape.
  • 381. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK254 Head Drum Tape Audio Tracks Slanted Tape Path Record / Play Head Figure 11.13: Helical recording with rotating heads.
  • 382. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK255 Record / Play Head A 90˚ Tape Record / Play Head B Figure 11.14: Tape contact to rotating head.
  • 383. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK256 Head A Head B 90˚ Wrap Angle 1/4 Revolution Head A Signal Head B Signal One Revolution Figure 11.15: Time compression to reduce wrap angle.
  • 384. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK257 Analog Cassette Track Pattern Right Side B Left Left Side A Guard Band Right Figure 11.16: Guard band between tracks on analog tape reduces cross-talk. Guard Band not necessary Tape Head A Head B Figure 11.17: Azimuthal recording.
  • 385. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK258 B A Tape - 20˚ Azimuth + 20˚ Azimuth Figure 11.18: Digital information on magnetic tape recorded longitudinally.
  • 386. CHAPTER 11. DIGITAL MAGNETIC RECORDING & PLAYBACK259 B A Tape Subcode Au ATF d io ATF Subcode Figure 11.19: Arrangement of signals on a tape. + X Y Figure 11.20: Exercise 11.7.
  • 387. Chapter 12 Heat 260
  • 388. CHAPTER 12. HEAT 261 Mechanical Friction Friction causes Friction causes Heating Heating Stylus Groove Friction Motion Friction causes causes Heating Heating Metallic Wire Electrical "Resistance" due + Vibrating Ions + + to Collisions of Electrons and Vibrating Ions + + + Moving Electrons Figure 12.1: Sources of heating in hi-
  • 389. due to mechanical friction and elec- trical friction".
  • 390. CHAPTER 12. HEAT 262 Heat Heat Current Current Diode Resistor Heat Heat Voice Coil Current Current Speaker Transistor Figure 12.2: Electrical friction" causes heating in ampli
  • 391. er components and voice coil.
  • 392. CHAPTER 12. HEAT 263 100 °C Pressure 0 °C Gas Alcohol Figure 12.3: Two types of thermometers: alcohol expansion thermometer and gas thermometer.
  • 393. CHAPTER 12. HEAT 264 Electrical Resistance in arbitrary units Temperature -50 °C 0 °C 50 °C 100 °C Cold Hot Figure 12.4: Temperature dependence of electric resistance of a semiconduc- tor. Battery Current Meter Resistance Thermometer Element Figure 12.5: Basic circuit for resistance thermometer.
  • 394. CHAPTER 12. HEAT 265 T at Room Temperature Laser Beam TbFeCo ≈ 1000 Å Aluminum T above Curie Section of Mini-Disc Section of Mini-Disc Temperature To Record Figure 12.6: Heating of spot on mini-disc for recording. Heat Flow Hot Cold Large Small Amplitude Amplitude Figure 12.7: Heat conduction along a bar between a hot body and a cold one.
  • 395. CHAPTER 12. HEAT 266 Hot Heat Cold Smaller Thermal Resistance Hot Heat Cold Larger Thermal Resistance Figure 12.8: Thermal resistance depends on length of heat conductor.
  • 396. CHAPTER 12. HEAT 267 Heat Smaller Thermal Hot Cold Resistance Cross-sectional Area Larger Thermal Hot Cold Resistance Heat Figure 12.9: Thermal resistance depends inversely on cross-sectional area of heat conductor.
  • 397. CHAPTER 12. HEAT 268 Warm Air Cold Air Source of Heat Figure 12.10: Transfer of heat in air by convection. Object Temperature = T Electromagnetic Vibrating Wave Charges + + Figure 12.11: Object at temperature T emits electromagnetic waves.
  • 398. CHAPTER 12. HEAT 269 Vibration At some Temperature of Atoms Vibration When Temperature has Increased of Atoms Figure 12.12: Thermal expansion of an object when heated. Brass Hot Steel Cool Flame Ice Figure 12.13: Bimetallic strip and its behavior when heated or cooled.
  • 399. CHAPTER 12. HEAT 270 Unmounted Diode Transistor Mounted Heat Sink with Heat Sink with Large Area Large Area Figure 12.14: Mounting of transistor and diode on heat sink to transfer heat away from devices by heat conduction.
  • 400. CHAPTER 12. HEAT 271 Hot Air Radiation Convection Holes Cold Air Holes Figure 12.15: Heat removal by convection and radiation. Materials with different Reset Button Expansion Amounts Too Hot Current In Open Circuit Current Out Figure 12.16: Action of circuit-breaker when too hot.
  • 401. CHAPTER 12. HEAT 272 Signal In Signal In Write Head Write Head Magnetic Film Motion Laser Off Spot Heated above Curie Temperature Spot Cools in Field of Write Head Heat to Record Recorded Figure 12.17: Thermo-magnetic recording on mini-Disc.
  • 402. Chapter 13 Mechanics 273
  • 403. CHAPTER 13. MECHANICS 274 Recording Head Tape Direction of Travel Distance travelled in Elapsed Time Figure 13.1: Speed of tape past recording head. Earth Figure 13.2: Time for a radio wave to go around the Earth at the equator.
  • 404. CHAPTER 13. MECHANICS 275 Rotation X Velocity is 0.4 m/sec, down Y Velocity is 0.4 m/sec, left Phono Record Figure 13.3: Speed of a recorded signal is the same at X and at Y; their velocities are di erent.
  • 405. CHAPTER 13. MECHANICS 276 Fixed Magnet S N Force + Fixed Magnet S N Force + Figure 13.4: Force on voice coil giving it a push or a pull depending on direction of current in voice coil.
  • 406. CHAPTER 13. MECHANICS 277 Pinch-Roller Tape Capstan Tape Direction Force Figure 13.5: Force on tape by capstan-pinch roller. Pinch-Roller Tape Force of Static Friction Tape Direction Capstan No Motion between Tape and Pinch-Roller and Capstan Figure 13.6: Static friction-force pulling on tape.
  • 407. CHAPTER 13. MECHANICS 278 CD Clips Figure 13.7: Releasing a CD from its case by applying a pressure on the clips with a
  • 408. nger.
  • 409. CHAPTER 13. MECHANICS 279 Tweeter has Small Inertia Woofer has Large Inertia Figure 13.8: Inertia of a tweeter is less than that of a woofer.
  • 410. CHAPTER 13. MECHANICS 280 Outer Ear Eardrum Sound Figure 13.9: Outer ear; ear drum's inertia limits response at frequencies above 20 kHz. Tone Arm Cartridge Stylus Weight of Cartridge for Tracking Groove in Phono Record Figure 13.10: Adjusted weight in cartridge for helping the stylus to track the groove in phono record.
  • 411. CHAPTER 13. MECHANICS 281 Speaker Mechanism Fixed Magnet N S Current (Audio) Information Tracks on CD Focus Coil Lens Moving Coil to Focus S N N S Laser Beam for CD Figure 13.11: Force of clamped magnet on a voice coil accelerates diaphragm in loudspeaker. Force of clamped magnet on focus coil accelerates focus lens in CD player.
  • 412. CHAPTER 13. MECHANICS 282 Wall Pulse on String Pulls on Wall Wall Pulls on String causing Pulse Wall Figure 13.12: Re ection of a pulse on a string clamped at wall and its inversion.
  • 413. CHAPTER 13. MECHANICS 283 Force on Voice Coil Bar Magnet N S Force on Bar Magnet Current Because of this, Magnet must be clamped Figure 13.13: Force on voice coil and force on magnet.
  • 414. CHAPTER 13. MECHANICS 284 Phono Record Constant Frequency of Rotation Both at same Frequency CD Variable Frequency of Rotation Both at same Frequency Figure 13.14: Waves recorded on a phono record and a CD.
  • 415. CHAPTER 13. MECHANICS 285 Phono Record r inner router Circumference at r inner 2 π r inner Circumference at router 2 π router Figure 13.15: Distances covered along outer track and inner track on a phono record.
  • 416. CHAPTER 13. MECHANICS 286 CD Rotation Rate increased to 500 rpm Rotation Rate at 200 rpm Figure 13.16: Frequency of rotation of a CD is made higher near the inner edge and lower near the outer edge to maintain constant linear speed on a tracks. 2000 rpm Record / Play Heads Drum Tape Guide Tape Figure 13.17: Rotation of drum head relative to magnetic tape in DAT.
  • 417. CHAPTER 13. MECHANICS 287 CD CD Ca se Li d A. Harder to Open CD CD Ca se Li d B. Easier to Open Figure 13.18: When same force is applied to the CD case lid, it is easier to open the lid near the edge because torque is larger there.
  • 418. CHAPTER 13. MECHANICS 288 Large Torque Small Torque Force Force Distance Distance Lid Lid Hinge Point Hinge Point A B Figure 13.19: For the same force exerted on lid, the torque is larger in B than in A. CD MD Figure 13.20: Moment of inertia of a CD is larger than that of a mini-Disc.