# Acoustics Midterm

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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)
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
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
• EQ
• levels
• Panning
• Arrangement
• Depth (reverb/delay)

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 Author: tenorsextets ID: 285861 Filename: Acoustics Midterm Updated: 2014-10-15 01:46:34 Tags: hastag Folders: Description: blargh Show Answers:

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