Acoustics Midterm

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tenorsextets
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285861
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Acoustics Midterm
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2014-10-14 21:46:34
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  1. acoustic isolation:
    minimize bleed between rooms
  2. acoustic separation:
    minimize bleed between mulitple mics within the same room
  3. transmission loss:
    how much sound is lost when it passes through something
  4. what will make a wall have more transmission loss?
    if it's thicker (it vibrates less)
  5. rigid fiberglass:
    it doesn't vibrate well, so it's good for absorbing sound in walls
  6. staggered studs:
    stagger the studs in the walls so they hold the wall in place but they don't vibrate on each other
  7. Types of acoustic treatment:
    • absorber (decrease reverb time)
    • diffusers
  8. Longitudinal waveform:
    air molecules compressing and expanding (like when you pluck a guitar string)
  9. Transverse waveform:
    the waveform you see drawn in pro tools
  10. Amplitude:
    height of the wave, relates to loudness
  11. RMS amplitude:
    mean of amplitude, about 70% of peak-to-peak amplitude
  12. λ wavelength:
    determines pitch of note
  13. Frequency formula:
    1130ft./sec. ÷ λ (wavelength)
  14. Frequency:
    # of cycles per second
  15. Timbre:
    sonic characteristic of the sound
  16. envelope:
    how amplitude changes over time (ADSR)
  17. Harmonics:
    layers of tones on the fundamental note
  18. Propagation:
    how sound travels from point A to B
  19. How does sound travel? (direction)
    360°
  20. When the day is drier, how does this affect sound?  Humid?
    Dry means it slows down, humid means it speeds up (more molecules to move)
  21. How to calculate distance:
    • Rate * Time = Distance (also for time delay)
    • Rate is always 1130ft./sec.
  22. Reflection:
    sound bouncing off something
  23. Absorption:
    sound NOT bouncing off something, friction causes sound to turn into heat
  24. Diffusion:
    scattering of sound
  25. diffraction:
    sound bending through an opening or around an object (causes acoustic shadow)
  26. Transmission:
    sound going through something (low freq. transmit better)
  27. Radiation Pattern:
    how sound propagates in 360°
  28. Phase:
    a point in time of a sound's wavelength
  29. interference:
    • Constructive: waves combine when they are in phase and add loudness
    • Destructive: wave out of phase and cancel each other out
  30. Flange:
    time delay of doubled sound (also comb filter)
  31. Chorus:
    pitch shift of doubled sound
  32. Beats:
    difference between 2 close frequencies and they begin to beat at that frequency
  33. binaural beat:
    2 different signals coming from either side that are beating
  34. What does a spaced pair rely on for stereo image?
    phase differences
  35. what does x/y pair rely on for stereo image?
    time delay (no phase, but not very wide)
  36. Sound pressure level:
    amount of air molecule displacement
  37. Dyne/cm2
    amount of molecules moving in 1 cm2
  38. formula to compare two distances
    20log(x/y)
  39. what is a decibel?
    a ration between 2 levels (at source and perceived)
  40. what is the lowest volume we can hear at?
    .0002 dyne/cm2
  41. dB SPL
    dB V
    dB m
    • air traveling through air
    • volts
    • watts (power; what is used mostly in the studio)
  42. what happens when you add or cut 3dB?
    boost/cut level by double/half, only sounds a little louder/softer to us
  43. when you add/cut 1dB?
    hardly noticeable
  44. Formula for adding/subtracting 2 decibel levels:
    10log(10x/10 ± 10y/10)
  45. Outer ear:
    • pinna (helps us tell up and down)
    • ear canal (takes sound to eardrum)
  46. Middle ear:
    • eardrum
    • ossicles (hammer, anvil, stirrup; connect eardrum to cochlea and help protect inner ear from damage when fatigued)
  47. Inner ear:
    • cochlea (filled w/ fluid, stereocilia transmit fluid vibration to auditory nerve)
    • auditory nerve (carry signal to brain)
  48. Doppler effect:
    when pitch changes as distance changes
  49. Combination tones:
    if 2 frequencies are greater than 50Hz apart, you will hear sum and difference of the 2 freq.
  50. What do the Fletcher-Munson curves tell us?
    hearing gets flatter as it gets louder, need to turn up bass when it's quiet
  51. measurement of perception of loudness is measured in:
    phons
  52. Ways to avoid masking:
    • EQ
    • levels
    • Panning
    • Arrangement
    • Depth (reverb/delay)

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