HVAC:| what does it stand for and what are the 3 things it causes?
 Heating, Ventilation, Air conditioning. Noise, flanking(noise brought in from another room through the ac vents), wind.
 definition: Gobo
 Used in the studio to isolate one sound source from another. Only effective at blocking frquencies whose WL’s are smaller than the dimensions of the gobo
 6 foot gobo, what freqs can it block?
 1130/6 = 188
 definition: diffractionWhy does it happen?
 the bending of a sound wave around an obstacle or object. This happens whenever the WL of a signal is greater than the dimensions of the obstacle.
 Lower Frequency means longer or shorter WL?
 Longer
 Mass Law: 2 times the mass equals___db increase in isolation
 6db. Increases isolation
 Mass Law: half the mass equals___db decrease in isolation
 6db. decreases isolation
 What does TL stand for? And what is it?
 Transmission Loss. A specific ratio in db between energy that goes in and goes out. The higher the TL, the better the isolation.
 TL of 500hz 36 db. Sound going in is 100 db. How loud is the sound coming out?
 65 db
 2x freq = ___db change in TL
 +6 db
 1/2 freq = ___ db change in TL
 -6 db
 2x mass = ___db change in tl
 +6 db
 What does STC stand for and what is it?
 Sound Transmission Class. A single number rating covering the TL performance of a construction between 125hz and 4khz.
 Is STC a ratio or a single number?
 Single number
 Frequencies between 125hz and 4khz at a level of 97 db going through a material with a STC of 27 will be how loud coming out?
 70 db
 What does NRC stand for and what is it?
 Noise Reduction Coefficient. An average rating of noise reduction. Average of 250hz,500hz,1khz,2khz. Is a number between 0-1.
 NRC is an average rating through what freqs?
 250hz, 500hz, 1khz, 2khz
 Is NRC specific or broad?
 Is TL specific or broad?
 specific
 Is A.C. specific or broad?
 specific
 Do TL and STC say anything about low frequencies?
 Nope
 What does AC stand for and what is it?
 Absorption Coefficient. A specific rating for each freq. Is a number between 0-1.
 A double wall partition can increase STC to ___db
 60db
 What does a double wall partition do?
 completely physically isolates one side of the wall from the other, making it very difficult for sound wave vibrations to pass through the structure.
 Use of metal studs generally improves isolation by ___db.
 5db
 Isolations principle tool is ____
 Mass
 True or False: Acoustically treating a room helps isolation.
 False, you stupid fucker.
 In a room, what 3 things happen to sound?
 reflection, absorption, diffusion.
 What is diffusion?
 The scattering of sound from a single strong discrete reflection to a broad array of lesser reflections spread in many different directions. Spreads sound evenlly while eliminating audible discrete echoes.
 Frequencies under 300 hz cause what problem in a room, and what are the solutions?
 Standing waves. Fix with Bass traps, membrane absorbers, and helmholtz resonators
 Frequences over 500 hz cause what problem in a room, and what are the solutions?
 Flutter echo. Fix with absorbers and diffusors.
 When were diffusors invented?
 1970’s
 What are the 3 types of absorbers
 Flexoral, frictional, resonant.
 What kind of absorber uses heat and is good around 125hz-500hz
 Friction
 How do you improve friction absorbers?
 Make them thicker or move them 3-6″ from wall. Moving improves them around 3-6″
 Why does moving a friction absorber away from the wall improve it?
 6″ is 1/4 of a 500hz WL.
 In a WL, the highest point(1/4 through the full cycle) is what 3 things?
 Antinode, max compression, max pressure
 In a WL, the midpoint(1/2 through the cycle) is what 2 things?
 Node, max velocity
 What type of absorber is flexoral
 membrane
 What kind of absorber can be tuned?
 Flexoral
 What range of Freq’s are flexorals good at?
 125hz-500hz
 What does a flexoral absorber do to freqs above 500hz?
 Reflects
 How does a helmholtz resonator work?
 The resonant absorber consists of an enclosed volume of air tuned to a low freq, with gaps or openings that allow low freq sound energy in. The air inside acts ke a type of spring on the columns of air entering the slots. The cavity can also be filled with frictional absorbent, with the effect of widening the bandwith of effective absorption to more generally absorb low freqs.
 Are helmholtz resonators broad or narrow band
 narrow
 Who is sabine
 Worked on reverb time, figured out rb60 formula.
 what is rb60
 number of seconds required for the intensity of the sound to drop from the starting level, by an amount of 60 dB
 What is the point of acoustically treating a control room?
 To hear only the sound coming out of the monitors
 What is a flutter echo
 rapidly repeating echoes at high frequencies, which occur in small enclosed spaces between closely spaced parallel walls.
 A0
 27.5hz, lowest note of piano
 C1
 31.5hz, lowest C on piano, 1st band in a graphic EQ
 C4
 261.63, middle c
 C8
 highest C on piano, 4186hz
 Speed of sound
 1130 ft/s, 1 ft/ms
 Fourier analysis
 breaking down sound into individual sine waves
 FFT
 Fast Fourier Transform, analyzing sound with 3d graph showing all the freqs
 What are the 10 bands of an eq?
 C1- 31.6C2- 63C3- 125C4- 250C5- 500C6- 1kC7- 2kC8- 4kC9- 8kC10-16k
 What is the Freq range of a piano?
 27.5hz to 4186hz
 Haas effect
 The brains ability to locate a sound source due to it’s earlier arrival to one ear than the other.
 Peak
 Highest pressure/amplitude
 RMS
 Root Means Squared. Average Amplitude.
 Crest Factor
 The Difference between RMS and Peak
 Transverse waves
 Displacement is perpendicular to motion. String wave. NOT A SOUND WAVE
 Longitudinal waves
 IS a sound wave. displacement is parallel to motion. Areas of compression and rarefaction.
 Phase.
 The phjase of a periodic wave refers to it’s current position with respect to the completetion of a full cycle, measured in degrees. 360 degrees in a cycle.
 Period
 the time it takes for a wavelength to complete once cycle
 JND
 Just noticable difference. Between 0.5 db and 3db
 Inverse square law
 2x distance from sound source= -6db
 Frequency of Alternating current power in USA
 60hz
 Frequency of Alternating current power in EU
 50hz
 10x power = ___db
 +10 db
 2x loud = ___db
 +10db
 2x SPL= ___db
 +6db
 2x distance
 +6db
 2x voltage
 +6db
 2x power = ___db
 +3db
 10 watts 2x loud = ___ watts
 100w
 10 watts 2x power = ___db
 +3db
 90db 2x power = ___db
 93
 90 db 2x loud= ___db
 100 db
 90 db 10x power= ___db
 100 db
 106dbSPL 2xSPL= ___db
 112 dbSPL
 phons
 the line where everything sounds as loud as a 1khz freq
 Parts of Outer ear
 Pinna, Ear Canal, tympanic membrane (eardrum)
 Parts of Middle ear
 Hammer, Anvil, Stirrup
 Parts of Inner Ear
 Cochlea, Round Window, oval window, basilar membrane, stereo cillia(hairs), periymph (fluid)
 What freqs do the base and tip of the cochlea pick up?
 Base: high freq, Tip: low freq
 Critcal bands
 Parts of the ear that determine d
 3 Ways to avoid masking
 EQ (2 guitars, change eq on one guitar), Pan, Arrangement
 below 35ms difference in arrival time to ears
 delay
 above 50ms difference in arrival time to ears
 echo
 between 35-50ms difference in arrival time to ears
 ambience
 5 kinds of stereo miking
 xy, spaced pair, blumlein, NOS, ORTF
 When did bbc begin regular stereo broadcasts
 1958
 3 interaural cues
 phase,spectrum, intensity
 On a SPL meter, use dbA weightings for ___ level sounds
 low
 On a SPL meter, use dbC weightings for ___ level sounds
 High
 Mixing domains
 Level, Frequency, Space
 Dynamic Processing
 Compression, limiting, dither