Microphone Techniques Flashcards
Spaced pair
two identical mics of any kind, often omnidirectional, placed generally somewhere between 3 ft. and 10 ft. apart, aimed directly toward the source
Boundary layer
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
Barrier miking
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
Baffled stereo
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
Blumlein
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
Close mic
placing a microphone near the source (a few inches) to get the characteristic of that source with minimal bleed from off-axis sources
Distant mic
placing a microphone away from the source to capture the whole source in an environment, usually by way of a room microphone
Coincident pair
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
Near-coincident pair
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
Decca Tree
involves three omnis, with the center microphone spaced slightly forward of the outer mics
Modified Decca tree
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
DIN stereo
stereo recording technique where two cardioid microphones are spaced 20 cm and angled 90 degrees creating the stereo image; very similar to ORTF
Drum overheads
microphones placed above the drum kit to capture the sound of the whole kit; usually in an XY or spaced pair configuration
Dummy head
models of human heads with pressure microphones
in the ears that can be used for originating binaural signals suitable for measurement or reproduction
HRTF
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
Gain before feedback
practical measure of how much a microphone can be amplified in a sound reinforcement system before causing audio feedback
Jecklin disc
sound-absorbing disk placed between two microphones to create an acoustic “shadow” from one microphone to the other
Kick drum tunnel
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
Leakage (bleed)
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
Matched pair
two microphones that sound the same
M-S
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
NOM
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
NOS
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°
On axis
in the direction of maximum sensitivity of a microphone; 0°
Off axis
not directly in front of a microphone or a loudspeaker
Off axis coloration
dull or colored effect on sound sources that are not
placed within the acceptance angle of the microphone
Open microphone
microphone that is connected to a broadcast or
recording system
ORTF
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
Parabolic reflector
dish with a diameter of .5-1 meter, used to ‘focus’ the
incoming sound wavefront at the microphone position, thus making it highly directional
Quiescent noise
residual noise produced by an audio device at its output terminals when no signal is present
Re-amp
process of running an already recorded signal back through an amplifier (and possibly speakers) of some sort to apply additional effects
Resonance
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
Resonate
to produce electrical or mechanical resonance
Room mic
microphone set up at some distance from a sound source in order to capture the natural ambience of the room
Rumble
undesirable low-frequency noise, caused by microphone stand noise, external noise, etc.
Spaced omni
method of stereo recording where two omnidirectional microphones are placed several feet apart in front of the sound source
Sphere stereo
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
Spot mic
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
3:1 rule
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
X-Y
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
