Microphone Techniques

Question 1

Spaced pair

Answer 1

two identical mics of any kind, often omnidirectional, placed generally somewhere between 3 ft. and 10 ft. apart, aimed directly toward the source

Question 2

Boundary layer

Answer 2

one or more small omnidirectional or cardioid condenser mic capsule(s) positioned near or flush with a boundary (surface) such as a floor, table, or wall

Question 3

Barrier miking

Answer 3

method of placing a microphone parallel and very close to a reflective surface to ensure that the direct sound and reflected sound reach the microphone at the same time; prevents phase cancellation issues that can occur when the direct sound arrives before the reflected sound

Question 4

Baffled stereo

Answer 4

generic term for a lot of different stereo techniques using an acoustic baffle to enhance the channel separation of the stereo signals; shadow effect from the baffle has a positive influence on the attenuation of off-axis sound sources, enhancing the channel separation

Question 5

Blumlein

Answer 5

two coincident bidirectional (figure of eight) mics placed at a 90° included angle from each other, and 45° off-axis from the source; each mic is sent to its own track or channel and panned hard left and right respectively

Question 6

Close mic

Answer 6

placing a microphone near the source (a few inches) to get the characteristic of that source with minimal bleed from off-axis sources

Question 7

Distant mic

Answer 7

placing a microphone away from the source to capture the whole source in an environment, usually by way of a room microphone

Question 8

Coincident pair

Answer 8

pair of microphones place on the same axis very close to each other, making sounds arrive at virtually the same time; uses the intensity differences of sound arriving at two mics to recreate the stereo field

Question 9

Near-coincident pair

Answer 9

introduce timing cues by spacing the mics slightly apart,
typically about the width of a human head (about 6.5” or 17 cm), with each mic essentially taking the place of one ear

Question 10

Decca Tree

Answer 10

involves three omnis, with the center microphone spaced slightly forward of the outer mics

Question 11

Modified Decca tree

Answer 11

Decca tree arrangement augmented with another wide spaced pair of omnis, one on either side of the tree to extend the width of the stereo capture, especially with larger ensembles

Question 12

DIN stereo

Answer 12

stereo recording technique where two cardioid microphones are spaced 20 cm and angled 90 degrees creating the stereo image; very similar to ORTF

Question 13

Drum overheads

Answer 13

microphones placed above the drum kit to capture the sound of the whole kit; usually in an XY or spaced pair configuration

Question 14

Dummy head

Answer 14

models of human heads with pressure microphones
in the ears that can be used for originating binaural signals suitable for measurement or reproduction

Question 15

HRTF

Answer 15

head-related transfer function; specific filtering because of
the presence of outer ears (pinnae), head, and shoulders, as well as interaural time differences and interaural amplitude differences for a given sound source location

Question 16

Gain before feedback

Answer 16

practical measure of how much a microphone can be amplified in a sound reinforcement system before causing audio feedback

Question 17

Jecklin disc

Answer 17

sound-absorbing disk placed between two microphones to create an acoustic “shadow” from one microphone to the other

Question 18

Kick drum tunnel

Answer 18

makeshift device occasionally used by recording studios to capture a more ambient kick drum sound; building a cavern or tunnel that extends from the front of a kick drum several feet out into the room

Question 19

Leakage (bleed)

Answer 19

spillover of sound from one source into another source’s microphone, usually due to the microphones being placed too close together or in a direction off-axis from the desired source

Question 20

Matched pair

Answer 20

two microphones that sound the same

Question 21

M-S

Answer 21

mid side; one mic (typically cardioid), signal A, is
pointed directly at the sound source, and its signal is routed to one track, panned center; second bidirectional mic (B) is positioned coincidently with mic A but at
a 90° angle from the source and first mic; two mic signals are combined (A+B) and routed to second track, panned hard left, corresponding to Mic B’s leftfacing on-axis pickup; mic signal (B) is split, its polarity is reversed (–180°), and it is again combined with the first mic (now A–B) to a third track, panned right

Question 22

NOM

Answer 22

number of open mics; each doubling of the number of open mics (NOM) cuts the gain by 3dB; as more mics are opened up the mic mixer reduces overall gain. If not, as mics open and close, the reverberation and ambient noise fluctuates unacceptably

Question 23

NOS

Answer 23

Nederlandse Omroep Stichting, the Dutch Broadcasting Foundation; nearcoincident stereo pair, which calls for two cardioid mics spaced 30 cm (12 inches) apart, at an included angle of 90°

Question 24

On axis

Answer 24

in the direction of maximum sensitivity of a microphone; 0°

Question 25

Off axis

Answer 25

not directly in front of a microphone or a loudspeaker

Question 26

Off axis coloration

Answer 26

dull or colored effect on sound sources that are not
placed within the acceptance angle of the microphone

Question 27

Open microphone

Answer 27

microphone that is connected to a broadcast or
recording system

Question 28

ORTF

Answer 28

Office de Radiodiffusion Télévision Française, named after the French broadcasting organization that developed it; consists of two cardioid mics with capsules spaced 17 cm (6.69 inches) apart and a 110° included angle between
them

Question 29

Parabolic reflector

Answer 29

dish with a diameter of .5-1 meter, used to ‘focus’ the
incoming sound wavefront at the microphone position, thus making it highly directional

Question 30

Quiescent noise

Answer 30

residual noise produced by an audio device at its output terminals when no signal is present

Question 31

Re-amp

Answer 31

process of running an already recorded signal back through an amplifier (and possibly speakers) of some sort to apply additional effects

Question 32

Resonance

Answer 32

tendency of a mechanical or electrical system to vibrate at a certain frequency when excited by an external force, and to keep vibrating after the excitation is removed

Question 33

Resonate

Answer 33

to produce electrical or mechanical resonance

Question 34

Room mic

Answer 34

microphone set up at some distance from a sound source in order to capture the natural ambience of the room

Question 35

Rumble

Answer 35

undesirable low-frequency noise, caused by microphone stand noise, external noise, etc.

Question 36

Spaced omni

Answer 36

method of stereo recording where two omnidirectional microphones are placed several feet apart in front of the sound source

Question 37

Sphere stereo

Answer 37

stereo miking technique based on simulating the acoustic field around the human head; 8-inch solid sphere separates two omnidirectional microphones, which are placed diagonally with their diaphragms flush with the surface of the sphere

Question 38

Spot mic

Answer 38

microphone purposely aimed toward a certain subject,
like a spotlight; usually the spot mic augments a stereo microphone array such as when recording an orchestra

Question 39

3:1 rule

Answer 39

when individually miking proximate sources, principle is based on the fact that the increased distance from each
source to the more distant mics will mean reduced leakage of the non-principal sources into each mic

Question 40

X-Y

Answer 40

the signals in the two channels are in phase because the two microphones used are “coincident” or very nearly so; two microphones with capsules placed on the same axis, 90 degrees apart