275b

absorbtion coeffecient

• Ia = sound level that is absorbed in dB
• Ir = sound level that is reflected in dB

if A is a small number not much absorbtion

Dense porous materials
Cloth, fiberglass, carpeting

harder to aborb

usually in corners of room

reverbation time in seconds

RT60 = 0.049 V / SA

the persistence of sound in a particular space after the original sound is removed

Sound wave that is
reflected off parallel
surfaces and travels
back on its self.

Stops standing waves and flutter echo.
• Acoustic boundaries that reflect the
sound in a number of directions.

acoustic
interference at the listening position.

will angle reflections
back into the control room.

solid state and tube

solid state requires phantom power

surface.....floor...wall...glass

most colored or erratic

smooth....especially older ones have less highs

flattest and most exteneded

condensor

ribbon

condensor

1. Ported
2. Electrically combining patterns

is how fast a sound wave
reaches its peak level

condensor

dynamic

1. Large diaphragm condensers
2. Small diaphragm condensers
3. New Ribbon mics
4. Dynamic mics
5. Old Ribbon mics

condensor good for clarinet

large diaphram

good for kick drum

good for bass and cello

large diaphram condensor

smooth and natural

condensor good for violin

roll-off

smooth

dynamic, bright, clean, less backround noise....versatile to most instruments, good for live sound

used between toms

dynamic

bass roll off

drums

Start with mics 1 – 3 and add others as
needed.
More realistic drum sound. Room sound is
important.

To get a fuller more ambient drum sound which can be blended with the close mics on
the drums. Only as good as the room sound the drums are in.
• Spaced mic pair 10 to 20 feet away.
• Coincident stereo mics 10 – 20 feet away

pressure zone mic

condensor mic

realistic accurate localization

head best in headphones

increase amplitude without changing harmonic content by applying more engery to the signal

same amp. at all freqs

3db/octive low pass filtered white noise, more like music

random movement of electrons

60hz part of noise floor

if the input signal goes above hte maximum level a circuit can reproduce the gain is passed and the output CLIPS

changes the frequency spectrum of the audio which causes distortion

the total range a system can handle

noise floor to the point of clipping

resistance that changes with frequency

indicates how much current is required for the device to work

some mics will loose some of the high freq signal over a longer cable

signal on a balanced cable is equal in amplitude but opposite in polarity between 2 wires, common mode rejection

because the dual noise in the two twisted wires cancel eachother out

controls grain of input signal

lowers the level of if the input to amp by a set amount. 10 or 20 db

INVERTS THE INPUT SIGNAL

48VDC

DIRECT INPUT- USED TO MATCH IMPEDANCE AND LEVELS

Ported mics use slots along the side of
the mic to create phase cancellation.

Omni
– Bidirectional

right to the listener

bounces off something and onto the listener

coming at the listener from all around him

constant speed
constant tension
tape position

From supply to take up

end of tape is on the outside, tape is stored on tape up reel

start of tape is on the outside.
Tape is stored on supply reel

control tape tension across the heads by controlling speed of supply and take up reels

keep tape positioned so tracks line up

move tape away from head when fast forwarding

rotates and works with the
pinch roller to pull tape across the
heads at a constant speed.

pinches tape against
capstan roller.

erase head
record head (sync head)
play head (repro head)