SOUND MANAGEMENT

26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

1
what your ears capture

Sound is a vibration
in
an
elastic
medium such as air,
water,
building
materials and earth.

- Wav...


Interference
there can be two kinds of interference patterns;



Constructive- Two waveforms are added together and cr...


Standing Waves
A standing wave is the result of the wave reflecting off the end of the tube
(whether closed or open) an...


Overtones
Overtones are the other frequencies besides the fundamental that exist in
musical instruments. Instruments of...
Sound has two main characteristics;


Frequency – measured in Hz (Hertz)



Pressure level – measured in dB (decibels)

...
Quality of sound depend on following;
Pitch-

Pitch is roughly equivalent to the frequency of a sound wave.
Frequencies ar...
Amplitude- determines the intensity, or loudness the size of the vibration

26 February 2014

nswickramasinghe@gmail.com/n...
In engineering the argument of the logarithm is
always a ratio of two quantities having the same
dimensions. In mathematic...
Gain

1

0 dB

2

3 dB

3

4 dB

4

6 dB

5

7 dB

200

23 dB

6

7 . 7 dB

100

20 dB

7

8.4 dB

80

19 dB

8

9 dB

40
...
logb(mn) = logb(m) + logb(n)
logb(m/n) = logb(m) – logb(n)
logb(mn) = n · logb(m)
26 February 2014

nswickramasinghe@gmail...
dB can be used to express the absolute level of the physical quantity. The
decibel is also commonly used as a measure of g...
The power P(dBm) in dBm is equal to 10 times the base 10 logarithm of the power
P(mW) in mill watts (mW) divided by 1 mill...
The power P(dBm) in dBm is equal to 10 times the base 10 logarithm of the power
P(mW) in mill watts (mW) divided by 1 mill...
dBm + dB = dBm

dBm – dB = dBm

dBm – dBm = dB
26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

15
3 dBm
1 dBm

+

0 dBm

26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

16
What will happened when this knobs are rotate
0
-3

0 dBm
3

-3 dBm

6

-6

-9

26 February 2014

9

-6 dBm

-9 dBm

nswic...
Take two short audio samples and play them, Human
listeners can detect the difference between two sound
sources that are p...
Convex Surface

Concave Surface

Corners

26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

19
Smooth Surface
θ1

Absorption Surface

P1

P2
P1
P1 = P2 = P3

θ2

θ1

θ2
θ3

P3

P3

P2
θ3 θ4

θ4
P1 > P2 > P3

θ1 = θ2 =...
The purpose of acoustic treatment is to improve the quality
of sound in a room/studio.
Diffusers
Traps
Absorbers

26 Febru...
26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

22


Two long sides and two
short sides from planks of
planed (using 15mm thick,
125mm wide, 2.4m)



then glued and screwe...
Main Isolation Window
2” Regiform Gap

Isolation Wall
Shell Wall

Cable Duct
Dry Wall
2”x2” wooden poles

26 February 2014...
Main Window Arrangement

Wooden poles

26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

25
Dynamic Microphone - A paper cylinder, onto which fine copper wire is
wound, is connected to a membrane which moves under ...
Crystal Microphone - The crystal microphone uses a thin strip of
piezoelectric material attached to a diaphragm. The two s...
Ribbon Microphones The air
movement associated with the sound
moves the metallic ribbon in the
magnetic field, generating ...
Work through each of these characteristics and determine your needs



Frequency Response



Impedance



Handling Noi...
Omni directional

Cardioid

Captures sound equally from all
directions.

Cardioid means "heart-shaped", which is
the type ...
Hypercardioid
This is exaggerated version of the cardioid
pattern. It is very directional and eliminates
most sound from t...
Frequency response refers to the way a microphone responds to different
frequencies. It is a characteristic of all microph...
All microphones have a specification referring to their impedance. This spec may be
written on the mic itself (perhaps alo...
Remember that the diaphragm works by converting vibrations from
sound waves into an electrical signal. Unless the micropho...
One of the most important factors in a
microphone is it's ability to respond
to rapidly changing sound waves. This
is know...
Sensitivity expresses the microphone's ability to convert
acoustic pressure to electric voltage. The sensitivity states wh...
26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

37
XLR Balance Connector

TRS Balance Connector

26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

38
RCA
(Radio Corporation of America)
connector, sometimes called a phono
connector or cinch connector, is a type of
electric...
XLR Balance Cable

26 February 2014

This means that much of the electromagnetic
interference will induce an equal noise v...
26 February 2014

nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com

41
1/4″ on the other hand comes in two styles:
balanced TRS (tip, ring, sleeve) and unbalanced
TS (tip, sleeve).

To be conti...
nswickramasinghe@gmail.com
Electrical and Electronic Engineer

26 February 2014

nswickramasinghe@gmail.com/nswickramasing...
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Sound management by lt ns wickramasinghe b sc e & e

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  • dB SPL (sound pressure level) dBq(quarter wave) dB SWL (sound power level)dBi(isotropic) dB SIL (sound intensity level) dB HL (hearing level) dBd(dipole) dBTP(true peak)
  • Sound management by lt ns wickramasinghe b sc e & e

    1. 1. SOUND MANAGEMENT 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 1
    2. 2. what your ears capture Sound is a vibration in an elastic medium such as air, water, building materials and earth. - Wave Length - Amplitude Rarefaction 26 February 2014 Compression Sound is the physical phenomenon that encourages the sense of hearing. It is generated by vibrated bodies in the form of waves rarefaction of compression and rarefaction in the air. nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 2
    3. 3.  Interference there can be two kinds of interference patterns;  Constructive- Two waveforms are added together and creates a louder sound  Destructive - Occurs when two waves are out of phase and creates a diminished waveform 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 3
    4. 4.  Standing Waves A standing wave is the result of the wave reflecting off the end of the tube (whether closed or open) and interfering with itself and sound is produced in an instrument by blowing it, only the waves that will fit in the tube resonate, while other frequencies are lost. The longest wave that can fit in the tube is the fundamental, other waves that fit are overtones 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 4
    5. 5.  Overtones Overtones are the other frequencies besides the fundamental that exist in musical instruments. Instruments of different shapes and actions produce different overtones 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 5
    6. 6. Sound has two main characteristics;  Frequency – measured in Hz (Hertz)  Pressure level – measured in dB (decibels) 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 6
    7. 7. Quality of sound depend on following; Pitch- Pitch is roughly equivalent to the frequency of a sound wave. Frequencies are measured in vibrations per second, or Hertz (Hz).Higher pitches vibrate more quickly, whereas low pitches vibrate more slowly 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 7
    8. 8. Amplitude- determines the intensity, or loudness the size of the vibration 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 8
    9. 9. In engineering the argument of the logarithm is always a ratio of two quantities having the same dimensions. In mathematics the argument of a logarithm function is simply a number. No dimensions involved. Example 102 = 100 log10(100) = 2 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 9
    10. 10. Gain 1 0 dB 2 3 dB 3 4 dB 4 6 dB 5 7 dB 200 23 dB 6 7 . 7 dB 100 20 dB 7 8.4 dB 80 19 dB 8 9 dB 40 16 dB 9 9 dB 20 13 dB 10 26 February 2014 Level 10 log (x) 10 dB 16 12 dB nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 10
    11. 11. logb(mn) = logb(m) + logb(n) logb(m/n) = logb(m) – logb(n) logb(mn) = n · logb(m) 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 11
    12. 12. dB can be used to express the absolute level of the physical quantity. The decibel is also commonly used as a measure of gain or attenuation, the ratio of input and output powers of a system, or of individual factors that contribute to such ratios. Examples; Voltage Acoustics Audio electronics Antenna measurements dBV(Rms) dB SPL dB(mW) dBi dBmV(Rms) dB SIL dBTP dBd dBμV dB SWL dBq dB HL 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 12
    13. 13. The power P(dBm) in dBm is equal to 10 times the base 10 logarithm of the power P(mW) in mill watts (mW) divided by 1 mill watt (mW): P(dBm) = 10 · log10( P(W) / 1mW) dBmV (decibels relative to one mill volt) is a measure of the signal strength in wires and cables at RF and AF frequencies. This unit is defined in terms of rootmean-square ( rms ) alternating current ( AC ) signal voltages in circuits in which the impedance is a pure resistance of some specified value. P(dBmV) = 20 · log10( P(V) / 1mV) 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 13
    14. 14. The power P(dBm) in dBm is equal to 10 times the base 10 logarithm of the power P(mW) in mill watts (mW) divided by 1 mill watt (mW): P(dBm) = 10 · log10( P(W) / 1mW) dBmV (decibels relative to one mill volt) is a measure of the signal strength in wires and cables at RF and AF frequencies. This unit is defined in terms of rootmean-square ( rms ) alternating current ( AC ) signal voltages in circuits in which the impedance is a pure resistance of some specified value. P(dBmV) = 20 · log10( P(V) / 1mV) 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 14
    15. 15. dBm + dB = dBm dBm – dB = dBm dBm – dBm = dB 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 15
    16. 16. 3 dBm 1 dBm + 0 dBm 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 16
    17. 17. What will happened when this knobs are rotate 0 -3 0 dBm 3 -3 dBm 6 -6 -9 26 February 2014 9 -6 dBm -9 dBm nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 3 dBm 6 dBm 9 dBm 17
    18. 18. Take two short audio samples and play them, Human listeners can detect the difference between two sound sources that are placed as little as three degrees apart, about the width of a person at 10 meters. Or play them 30microseconds apart 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 18
    19. 19. Convex Surface Concave Surface Corners 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 19
    20. 20. Smooth Surface θ1 Absorption Surface P1 P2 P1 P1 = P2 = P3 θ2 θ1 θ2 θ3 P3 P3 P2 θ3 θ4 θ4 P1 > P2 > P3 θ1 = θ2 = θ3 = θ4 θ1 = θ2 = θ3 = θ4 Diffusion Surface P5 P2 P1 26 February 2014 P3 P4 P1 = P2 = P3 = P4 = P5 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 20
    21. 21. The purpose of acoustic treatment is to improve the quality of sound in a room/studio. Diffusers Traps Absorbers 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 21
    22. 22. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 22
    23. 23.  Two long sides and two short sides from planks of planed (using 15mm thick, 125mm wide, 2.4m)  then glued and screwed the corners.  Rockwool and foam fit inside the frame.  To secure the 30 mm Rockwool slab, then fitted 20mm wooden batten around the inside of the frame, set back from the front edge by 35mm It would sit 5mm behind the front of the frame. This meant that when the nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 23 Auralex foam was glued.  26 February 2014
    24. 24. Main Isolation Window 2” Regiform Gap Isolation Wall Shell Wall Cable Duct Dry Wall 2”x2” wooden poles 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 24
    25. 25. Main Window Arrangement Wooden poles 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 25
    26. 26. Dynamic Microphone - A paper cylinder, onto which fine copper wire is wound, is connected to a membrane which moves under the force of sound pressure created by the sound source. This coil is in a narrow gap with a high magnetic field created by a permanent magnet. When the coil moves in this magnetic field, it produces a voltage identical to the sound causing the movement. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 26
    27. 27. Crystal Microphone - The crystal microphone uses a thin strip of piezoelectric material attached to a diaphragm. The two sides of the crystal acquire opposite charges when the crystal is deflected by the diaphragm. The charges are proportional to the amount of deformation and disappear when the stress on the crystal disappears. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 27
    28. 28. Ribbon Microphones The air movement associated with the sound moves the metallic ribbon in the magnetic field, generating an imaging voltage between the ends of the ribbon which is proportional to the velocity of the ribbon - characterized as a "velocity" microphone. Condenser Microphones- Sound pressure changes the spacing between a thin metallic membrane and the stationary back plate. The plates are charged to a total charge 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 28
    29. 29. Work through each of these characteristics and determine your needs   Frequency Response  Impedance  Handling Noise  Transient Time  26 February 2014 Directionality Sensitivity nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 29
    30. 30. Omni directional Cardioid Captures sound equally from all directions. Cardioid means "heart-shaped", which is the type of pick-up pattern these mics use. Sound is picked up mostly from the front, but to a lesser extent the sides as well. Uses Capturing ambient noise; Situations where sound is coming from many directions; Situations where the mic position must remain fixed while the sound source is moving. 26 February 2014 Uses Emphasising sound from the direction the mic is pointed whilst leaving some latitude for mic movement and ambient noise. nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 30
    31. 31. Hypercardioid This is exaggerated version of the cardioid pattern. It is very directional and eliminates most sound from the sides and rear. Due to the long thin design of hypercardioids, they are often referred to as shotgun microphones. Bidirectional Uses a figure-of-eight pattern and picks up sound equally from two opposite directions. Uses As you can imagine, there aren't a lot of situations which require this polar Uses pattern. One possibility would be an Isolating the sound from a subject or direction interview with two people facing each when there is a lot of ambient noise; Picking up other (with the microphone between sound from a subject at a distance. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 31 them).
    32. 32. Frequency response refers to the way a microphone responds to different frequencies. It is a characteristic of all microphones that some frequencies are exaggerated and others are attenuated (reduced) More importantly, it should be noted that a flat frequency response is not always the most desirable option. In many cases a tailored frequency response is more useful. For example, a response pattern designed to emphasise the frequencies in a human voice would be well suited to picking up speech in an environment with lots of low-frequency background noise. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 32
    33. 33. All microphones have a specification referring to their impedance. This spec may be written on the mic itself (perhaps alongside the directional pattern), or you may need to consult the manual or manufacturer's website. You will often find that mics with a hard-wired cable and 1/4" plug are high impedance, and mics with separate balanced audio cable and XLR connector are low impedance.  There are three general classifications for microphone impedance. Different manufacturers use slightly different guidelines but the classifications are roughly:    Low Impedance (less than 600Ω) Medium Impedance (600Ω - 10,000Ω) High Impedance (greater than 10,000Ω) Note that some microphones have the ability to select from different impedance ratings. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 33
    34. 34. Remember that the diaphragm works by converting vibrations from sound waves into an electrical signal. Unless the microphone has some sort of protection system, the diapragm can't tell the difference between a desirable sound wave vibration and any other sort of vibration (such as a person tapping the microphone casing). Any sort of vibration at all will become part of the generated audio signal. If your mic is likely to be subjected to any sort of handling noise or vibration, you will need a mic which will help prevent this noise from being picked up. High quality hand-held mics usually attempt to isolate the diaphragm from vibrations using foam padding, suspension, or some other method. Low quality mics tend to transfer vibrations from the casing right into the diaphragm, resulting in a terrible noise. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 34
    35. 35. One of the most important factors in a microphone is it's ability to respond to rapidly changing sound waves. This is known as "transient response". The acoustic sound wave physically moves the diaphragm. The amount of time it takes for this to happen depends on the weight of the diaphragm material. Of course, the response time is longer for the heavier diaphragm material of the dynamic to react over the lightweight, thinner condenser element. 26 February 2014 Transient time of Condenser Mic, Ribbon Mic and Dynamic Mic nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 35
    36. 36. Sensitivity expresses the microphone's ability to convert acoustic pressure to electric voltage. The sensitivity states what voltage a microphone will produce at a certain sound pressure level. A microphone with high sensitivity will give a high voltage output and will therefore not need as much amplification (gain) as a model with lower sensitivity. In applications with low sound pressure levels, a microphone with a high sensitivity is required in order to keep the amplification noise low. According to the IEC 268-4 norm, the sensitivity is measured in mV per Pascal at 1 kHz (measuring microphones at 250 Hz). 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 36
    37. 37. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 37
    38. 38. XLR Balance Connector TRS Balance Connector 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 38
    39. 39. RCA (Radio Corporation of America) connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals. TS Unbalance Connector 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 39
    40. 40. XLR Balance Cable 26 February 2014 This means that much of the electromagnetic interference will induce an equal noise voltage in each wire. Since the amplifier at the far end measures the difference in voltage between the two signal lines, noise that is identical on both wires is rejected. The wires are also twisted together, to reduce interference from electromagnetic induction. nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 40
    41. 41. 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 41
    42. 42. 1/4″ on the other hand comes in two styles: balanced TRS (tip, ring, sleeve) and unbalanced TS (tip, sleeve). To be continued with Public Address Systems 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 42
    43. 43. nswickramasinghe@gmail.com Electrical and Electronic Engineer 26 February 2014 nswickramasinghe@gmail.com/nswickramasinghe@yahoo.com 43

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