Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Audio Engineering 201: "How to Sound"

6,773 views

Published on

An introduction to audio engineering. Here we skip over the basics so that we can delve deep into the issues that come up when designing, deploying, powering, tuning, and protecting a medium to large-sized loudspeaker system. We will talk about crossovers, coverage patterns, speaker arrays, delays, limiters, choosing the right amplifier power for the speakers, field repairs, and more.

Original class recordings:
https://www.youtube.com/watch?v=pHRYpP_cSqs
https://www.youtube.com/watch?v=26lZdc9HhtI

Published in: Engineering
  • DOWNLOAD THIS BOOKS INTO AVAILABLE FORMAT (2019 Update) ......................................................................................................................... ......................................................................................................................... Download Full PDF EBOOK here { https://soo.gd/irt2 } ......................................................................................................................... Download Full EPUB Ebook here { https://soo.gd/irt2 } ......................................................................................................................... Download Full doc Ebook here { https://soo.gd/irt2 } ......................................................................................................................... Download PDF EBOOK here { https://soo.gd/irt2 } ......................................................................................................................... Download EPUB Ebook here { https://soo.gd/irt2 } ......................................................................................................................... Download doc Ebook here { https://soo.gd/irt2 } ......................................................................................................................... ......................................................................................................................... ................................................................................................................................... eBook is an electronic version of a traditional print book THIS can be read by using a personal computer or by using an eBook reader. (An eBook reader can be a software application for use on a computer such as Microsoft's free Reader application, or a book-sized computer THIS is used solely as a reading device such as Nuvomedia's Rocket eBook.) Users can purchase an eBook on diskette or CD, but the most popular method of getting an eBook is to purchase a downloadable file of the eBook (or other reading material) from a Web site (such as Barnes and Noble) to be read from the user's computer or reading device. Generally, an eBook can be downloaded in five minutes or less ......................................................................................................................... .............. Browse by Genre Available eBooks .............................................................................................................................. Art, Biography, Business, Chick Lit, Children's, Christian, Classics, Comics, Contemporary, Cookbooks, Manga, Memoir, Music, Mystery, Non Fiction, Paranormal, Philosophy, Poetry, Psychology, Religion, Romance, Science, Science Fiction, Self Help, Suspense, Spirituality, Sports, Thriller, Travel, Young Adult, Crime, Ebooks, Fantasy, Fiction, Graphic Novels, Historical Fiction, History, Horror, Humor And Comedy, ......................................................................................................................... ......................................................................................................................... .....BEST SELLER FOR EBOOK RECOMMEND............................................................. ......................................................................................................................... Blowout: Corrupted Democracy, Rogue State Russia, and the Richest, Most Destructive Industry on Earth,-- The Ride of a Lifetime: Lessons Learned from 15 Years as CEO of the Walt Disney Company,-- Call Sign Chaos: Learning to Lead,-- StrengthsFinder 2.0,-- Stillness Is the Key,-- She Said: Breaking the Sexual Harassment Story THIS Helped Ignite a Movement,-- Atomic Habits: An Easy & Proven Way to Build Good Habits & Break Bad Ones,-- Everything Is Figureoutable,-- What It Takes: Lessons in the Pursuit of Excellence,-- Rich Dad Poor Dad: What the Rich Teach Their Kids About Money THIS the Poor and Middle Class Do Not!,-- The Total Money Makeover: Classic Edition: A Proven Plan for Financial Fitness,-- Shut Up and Listen!: Hard Business Truths THIS Will Help You Succeed, ......................................................................................................................... .........................................................................................................................
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • DOWNLOAD FULL BOOKS, INTO AVAILABLE FORMAT ......................................................................................................................... ......................................................................................................................... 1.DOWNLOAD FULL. PDF EBOOK here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... 1.DOWNLOAD FULL. EPUB Ebook here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... 1.DOWNLOAD FULL. doc Ebook here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... 1.DOWNLOAD FULL. PDF EBOOK here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... 1.DOWNLOAD FULL. EPUB Ebook here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... 1.DOWNLOAD FULL. doc Ebook here { https://tinyurl.com/y3nhqquc } ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .............. Browse by Genre Available eBooks ......................................................................................................................... Art, Biography, Business, Chick Lit, Children's, Christian, Classics, Comics, Contemporary, Cookbooks, Crime, Ebooks, Fantasy, Fiction, Graphic Novels, Historical Fiction, History, Horror, Humor And Comedy, Manga, Memoir, Music, Mystery, Non Fiction, Paranormal, Philosophy, Poetry, Psychology, Religion, Romance, Science, Science Fiction, Self Help, Suspense, Spirituality, Sports, Thriller, Travel, Young Adult,
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here

Audio Engineering 201: "How to Sound"

  1. 1. SOUND 201 Large-scale Sound Reinforcement Langton Labs August 18-19th, 2014 Michael Broxton Contact: broxton@gmail.com
  2. 2. WHAT IS INTHE CLASS? • The physical behavior of sound & the sound field • The human perception of sound Today we will discuss the fundamental nature of sound. Tomorrow we will discuss its reproduction using loudspeakers. • Understanding loudspeaker specifications • Moar volume: loudspeaker arrays • Tuning the system: crossover, gain structure, delays, and EQ • Tips for running live sound
  3. 3. THE SOUND WAVE Sound is our perception of a mechanical wave of pressure or displacement traveling through a medium such as air. Broadly speaking, a sound wave has three properties that carry information that determine its behavior.
  4. 4. THE SOUND WAVE Sound is our perception of a mechanical wave of pressure or displacement traveling through a medium such as air. Broadly speaking, a sound wave has three properties that carry information that determine its behavior.
  5. 5. THE SOUND WAVE Image credit: Daniel Russel. Acoustics andVibration Animations Although sound waves coming from multiple sources sum together in a straight-forward manner…
  6. 6. THE SOUND WAVE Image credit: Daniel Russel. Acoustics andVibration Animations Although sound waves coming from multiple sources sum together in a straight-forward manner…
  7. 7. THE SOUND WAVE Image credit: Daniel Russel. Acoustics andVibration Animations Although sound waves coming from multiple sources sum together in a straight-forward manner… …their summation can lead to complex patterns of constructive and destructive interference.
  8. 8. THE SOUND FIELD Of course, sound waves are not 1-dimensional. They travel through space, and the evolve over time. y x Click on the image to try this demo online using Johannes Singler’s WaveWorkshop
  9. 9. THE SOUND FIELD An ideal point source radiates sound equally in all directions as a spherical wavefront. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop
  10. 10. THE SOUND FIELD When wavefronts from two point sources (e.g. stereo loudspeakers) interact, there is a pattern of interference. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop
  11. 11. THE SOUND FIELD Null zones of destructive interference span areas of constructive interference where sound amplitude is doubled*. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop * - But perceived “loudness” is not doubled! We’ll cover that later…
  12. 12. THE SOUND FIELD The spacing between the point sources effects the interference pattern. As point sources get closer together, the null zones get farther apart, and vice versa. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop When sources are really close together, they form a dipole radiator that acts like a directional point source. Example: mid and high range driver in the same loudspeaker. Example: two adjacent mid-range drivers in the same loudspeaker.
  13. 13. SPEAKER CROSSOVERS This pattern of interference must be considered when designing loudspeakers with multiple drivers.
  14. 14. THE SOUND FIELD The frequency of the sound also changes interference pattern and spacing between the null zones. Low frequencies push the null zones apart, but they also grow larger and more noticeable to the listener. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop High frequencies can push the null zones so close together that they are so small as to not be noticeable at all. Example: stereo subwoofers Example: stereo tweeters
  15. 15. THE SOUND FIELD For mid/high frequencies we begin to perceive a stereo effect when the spacing between the sources is large enough, despite the dense interference pattern. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop
  16. 16. THE SOUND FIELD But sub-woofers are more tricky, though, because the pattern of interference is human-scale. We also do not tend to perceive a stereo image at low frequencies. Click on the image to try this demo online using Johannes Singler’s WaveWorkshop
  17. 17. SUB-WOOFER ARRAYS To address this problem, it is best to place subs near each other so that they appear as a single, coherent source. A rear-delay or end-fire array, used in conjunction the the proper delays, can reduce the amount of sound energy emanating from the back and sides of the stage. There are many clever ways to array sub-woofers to achieve advantageous cancellation effects. Often these are used to achieve a cardioid pattern of sound energy.
  18. 18. OTHER FACTORS There are many other important factors that effect the sound field. • Reflection … off walls, the ground. Plays a particularly important role indoors. • Refraction … around objects, around people. • Absorption … helps to attenuate reflections, or as the sound passes through humid air. • Scattering … diffuses sound energy, spreading it out in a random manner. These are topics that are important to consider in room acoustics. Another class!!
  19. 19. FOR MORE FUN EXAMPLES Try the Ripple Tank app (mac, iPad, or web)
  20. 20. LET’STALK ABOUT REAL SOUNDS They are the (linear) sum of many individual pure waveforms each with their own frequency and phase. Add together Final waveform The real sounds we encounter in the world are complex.
  21. 21. DUAL DOMAINS The Fourier transform is the mathematical tool we use to decompose a time signal into its frequency components, and vice versa. It is quite useful, but no matter how complicated the time waveform, the Fourier transform only gives us information about the average power in each frequency over all time. However we simultaneously perceive sound in terms of both time and frequency.
  22. 22. A MIXED REPRESENTATION Our ear does a neat trick: it decomposes the sound into a mixed time-frequency representation. Time (linear) Frequency (logarithmic) We can do this digitally (albeit imperfectly) using a tool called a spectrogram or a windowed or short-time Fourier transform (STFT). ! Using the spectrogram, we can see both spectral and temporal aspects in the music in a way that is similar to how we hear it.
  23. 23. GETTO KNOW YOUR FREQUENCIES “Subs” “Mids" “Tops”
  24. 24. PERCEPTION OF FREQUENCY: PITCH The human range of hearing is from about 20 Hz to 20KHz Frequency (logarithmic) We perceive pitch logarithmically in relation to frequency. ! Each frequency doubling is perceived as an equal (perceptually linear) increase in pitch: i.e. one “octave.”
  25. 25. PERCEPTION OF SOUND INTENSITY: LOUDNESS Next let’s talk about another perceptual phenomenon: loudness. Unit: dBu (voltage) or dBm (power) Oscilloscope Sound pressure Measurement Device Phenomenon Sound Pressure Meter Electricity Human Perception Voltage, current, or power Acoustic Energy “Loudness” Unit: dB SPL Your Ear Unit: Phon
  26. 26. BRIEF DIGRESSION:THE DECIBEL Our perception of loudness is also logarithmic. What we perceive to be 2x as “loud” is actually 10x the acoustic energy intensity. What we perceive to be 4x as “loud” is actually 100x the acoustic energy intensity. What we perceive to be 8x as “loud” is actually 1000x the acoustic energy intensity. etc. The decibel is a logarithmic measure relative to some reference level.
  27. 27. = = µ ( ) Again, we use this because it is convenient, and matches our perceptual experience. For example: dB sound pressure level or db SPL BRIEF DIGRESSION:THE DECIBEL
  28. 28. BRIEF DIGRESSION:THE DECIBEL Depending on where you are in the signal chain, you may find yourself using a different one of these scales. But they are all compatible, inasmuch as a +10dB in one scale leads to a +10dB increase in the others! It is designed to be simple and intuitive. Electrical Energy = = µ ( ) = = Unit: dBu = = Voltage e.g. Mixers Unit: dBm Power e.g.Amplifiers Acoustic Energy Unit: db SPL Pressure Power Unit: db SWL Loudness A phon is equal to the sound pressure level (in db SPL) of an equivalently “loud” 1-KHz tone. = - = Beware… there are many decibel scales & reference levels!
  29. 29. CONTROLLINGVOLUME OR “GAIN” Unit: dBu (voltage) or dBm (power) Oscilloscope Sound pressure Measurement Device Phenomenon Sound Pressure Meter Electricity Human Perception Voltage, current, or power Acoustic Energy “Loudness” Unit: dB SPL Your Ear Unit: Phon
  30. 30. LEARNINGTOTHINK INTERMS OF DECIBELS +3dB is: 2x the acoustic power but only 1.23x as “loud” +6dB is: 4x the acoustic power but only 1.5x as “loud” +10dB is: 10x the acoustic power and 2x as “loud” Some implications to think about: • A 1-2 dB change in volume is barely perceptible • Doubling amplifier power does not double loudness
  31. 31. SOUND INTENSITY AND ACOUSTIC ATTENUATION Unit: dBu (voltage) or dBm (power) Oscilloscope Sound pressure Measurement Device Phenomenon Sound Pressure Meter Electricity Human Perception Voltage, current, or power Acoustic Energy “Loudness” Unit: dB SPL Your Ear Unit: Phon
  32. 32. SOUND ATTENUATION OVER DISTANCE
  33. 33. SOUND ATTENUATION OVER DISTANCE
  34. 34. PERCEPTION OF SOUND INTENSITY:“LOUDNESS” Unit: dBu (voltage) or dBm (power) Oscilloscope Sound pressure Measurement Device Phenomenon Sound Pressure Meter Electricity Human Perception Voltage, current, or power Acoustic Energy “Loudness” Unit: dB SPL Your Ear Unit: Phon
  35. 35. EQUAL-LOUDNESS CONTOURS The equal loudness curves are psychoacoustic measurements of how humans perceive loudness.
  36. 36. THE RANGE OF HUMAN HEARING They can help us to draw a boundary around the perceptible range of sounds.
  37. 37. THE RANGE OF HUMAN HEARING Or the sounds that represent speech, or music.
  38. 38. As the sound engineer, it is your job to protect your audience from hearing damage. • Use limiters to prevent transients from damaging hearing. MEASURING NOISE EXPOSURE Measures you should take: • Measure the average noise “exposure” over the scale of minutes or hours. Rough guidelines for dance music: • 90-100 dB SPL (average) is a good, relatively safe volume early or late in the night. • 100-110 dB SPL (average) is a good sustained level at the peak. • Beyond this, you risk damaging ears and speakers.
  39. 39. PROTECTYOUR HEARING! More info: https://www.etymotic.com/pdf/er_noise_exposure_whitepaper.pdf Occupational Safety and Health Administration (OSHA) & National Institute for Occupational Safety and Health (NIOSH)
  40. 40. PROTECTYOUR HEARING! Passive Protection Active $300$10 $150
  41. 41. PART II • The physical behavior of sound & the sound field • The human perception of sound • Understanding loudspeaker specifications Yesterday we discussed the fundamental nature of sound. Today we will discuss its reproduction using loudspeakers. • Moar volume: loudspeaker arrays • Tuning the system: crossover, gain structure, delays, and EQ • Tips for running live sound
  42. 42. THE IDEALSVS. REALITY The ideal loudspeaker would: ! … radiate sound like an ideal point or line source … ! … play music with a flat frequency response over all audible frequencies … ! … and get arbitrarily loud. This is not physically possible!
  43. 43. THE IDEALSVS. REALITY For starters, different frequencies of sound have different properties. Low frequencies: • Diffract more, reflect less • Require a driver that can move a lot of air! • Are highly omnidirectional High frequencies: • Diffract less, reflect more • Requires a driver that can move very fast! • Are highly directional
  44. 44. LOUDSPEAKER DIRECTIVITY (at least down to the low frequencies) A good loudspeaker has been optimized to produce roughly equal acoustic power over a limited arc of angles. Managing the pattern of sound dispersion is called pattern control and it is the key to understanding how multiple loudspeakers interact.
  45. 45. LOUDSPEAKER DIRECTIVITY The first consequence of this is that you should put people’s ears where the speaker is producing the best possible sound.
  46. 46. LOUDSPEAKER DIRECTIVITY As an aside: this has implications for where you place stereo loudspeakers, and the directions you point them.
  47. 47. ANATOMY OF A LOUDSPEAKER Bass-reflex vent Bass-reflex vents Direct Radiating Woofer Horn-loaded mid Horn-loaded HF compression driver
  48. 48. THE IMPORTANCE OFTHE ENCLOSURE
  49. 49. DIRECT RADIATING LOUDSPEAKERS Direct Radiator Reflex Enclosure
  50. 50. HORN LOUDSPEAKERS
  51. 51. FOLDED HORN
  52. 52. OUR NEW SOUND SYSTEM LA400 LA460 LA215 LF Subsystem: 1x 15-in, vented HF Subsystem: 1x 2-in exit/3-in voice coil compression driver on Wave Guid Plate. LF Subsystem: 1x 15-in, vented HF Subsystem: 1x 1.4-in exit/ 1.75-in voice coil compression driver on constant directivity horn. MF Subsystem: 1x 8-in cone, horn-loaded LF Subsystem: 12-in woofer, bent bass horn LF Subsystem: 2x 18-in, vented LF Subsystem: 2x 18-in, vented LA128 LA128z Coverage angle (+/- 6dB): 180° Coverage angle (+/- 6dB): 360° Coverage angle (+/- 6dB): 360° Coverage angle (+/- 6dB): 90° Conical Coverage angle: 60° x 45°
  53. 53. OUR NEW SOUND SYSTEM LA400 Power handling: 500W @ 8 Ω Freq response: 45-250 Hz Sensitivity: 107 dB SPL/W @ 1m LA215 Power handling: 600W @ 8 Ω Freq response: 69 Hz - 18 KHz Sensitivity: 97 dB SPL/W @ 1m LA460 Power handling: full range: 500W @ 8 Ω bi-amp (LF/MF): 500W @ 8 Ω bi-amp (HF): 150W @ 8 Ω Freq response: 62 Hz - 20 KHz Sensitivity: full range: 97 dB SPL bi-amp (LF/MF): 97 dB SPL bi-amp (HF): 108 dB SPL LA128 Power handling: 1600W @ 4Ω Freq response: 31-200 Hz Sensitivity: 98 dB SPL/W @ 1m LA128z Power handling: 2000W @ 4Ω Freq response: 31-200 Hz Sensitivity: 98 dB SPL/W @ 1m
  54. 54. LOUDSPEAKER ARRAYS Line Source ArrayPoint Source Array In order to create high sound pressure levels over a large areas, you need to array many loudspeakers together.
  55. 55. LOUDSPEAKER ARRAYS Image credits: McCarthey, Bob. Meyer Design Reference for Sound Reproduction. 1998
  56. 56. LOUDSPEAKER ARRAYS Image credits: McCarthey, Bob. Meyer Design Reference for Sound Reproduction. 1998
  57. 57. ANOTHER FUN LOUDSPEAKER SYSTEM 20 x 12" Mid-bass drivers in 10 cabinets (2500 Watts / cabinet) 18 x 21" drivers w/ 6” voice coil 15mm excursion, & neodymium magnets (4000W / 2 drivers) 12” and 2” horn-loaded drivers,“cat’s eyes” horn flare
  58. 58. SYSTEM PROCESSOR
  59. 59. SYSTEM PROCESSOR 1. Configure crossover frequencies 2.Add driver alignment delays, polarity, and EQ 3. Calibrate the gain structure & set the limiters 4. Rough balancing of frequency response 5. Careful system EQ
  60. 60. CONFIGURE CROSSOVER FREQUENCIES
  61. 61. SYSTEM PROCESSOR 1. Configure crossover frequencies 2. Add driver alignment delays, polarity, and EQ 3. Calibrate the gain structure & set the limiters 4. Rough balancing of frequency response 5. Careful system EQ
  62. 62. DRIVER ALIGNMENT DELAYS, POLARITY AND EQ Bi-amplified loudspeaker Speaker system with flown tops Sub Top 2m 5m 5.4m Delay the subs by: 0.4m (1.2ms)
  63. 63. SYSTEM PROCESSOR 1. Configure crossover frequencies 2.Add driver alignment delays, polarity, and EQ 3. Calibrate the gain structure & set the limiters 4. Rough balancing of frequency response 5. Careful system EQ
  64. 64. CALIBRATE GAIN STRUCTURE & SET LIMITERS As a general rule, use an amplifier delivering 1.5x - 2x the speaker's average ("RMS") power rating. Note: amplifiers are a fixed-gain device. the knob of the front of the amplifier attenuates the input, rather than “turning up” the output.
  65. 65. CALIBRATE GAIN STRUCTURE & SET LIMITERS Setting gain structure involves two steps: 1. adjust levels so that all parts of the signal chain clip at the same time. 2. use limiters to prevent the amplifiers from clipping
  66. 66. SYSTEM PROCESSOR 1. Configure crossover frequencies 2.Add driver alignment delays, polarity, and EQ 3. Calibrate the gain structure & set the limiters 4. Rough balancing of frequency response 5. Careful system EQ
  67. 67. SYSTEM PROCESSOR 1. Configure crossover frequencies 2.Add driver alignment delays, polarity, and EQ 3. Calibrate the gain structure & set the limiters 4. Rough balancing of frequency response 5. Careful system EQ
  68. 68. POWERINGTHE SOUND SYSTEM There are a few things to consider here: • Power to the mixer, stage monitors, laptops, etc. should be a single independent power circuit. • Each amplifier will take somewhere between 5-15A on a normal 120V AC line. AC circuits are typically 20-30A. Plan accordingly! • Make sure your extension cables are rated for the power you are delivering. • Avoid power strips. Plug amps directly into the line, using splitters if necessary.
  69. 69. TROUBLESHOOTING Blown fuse / tripped breaker Unexpected resonance in a speaker Clipping A dead speaker or amp If this happens: Do this: Generator runs out of gas Hang your head in shame. :) Reset breakers. Replace fuse. Adjust crossover LPF Turn down the mixer Depends on the situation… Late DJ Have laptop or DJ iPod at the ready Mic feedback during live act Reduce gain, twiddle EQ
  70. 70. THANKS! Michael Broxton Contact: broxton@gmail.com

×