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In live sound mixing, GBF is dependent on a wide variety of conditions: the pickup pattern (polar pattern) of the microphone, the frequency response of the microphone and of the rest of the sound system, the number of active microphones and loudspeakers, the acoustic conditions of the environment
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and hypercardioid pickup patterns are designed with reduced sensitivity to the rear (cardioid) or to an angle between the side and the rear (hypercardioid). Such microphones are aimed such that their pickup pattern is weakest in the direction of the loudspeakers. This is especially useful in the
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is a factor, with larger and heavier designs capable of delivering greater GBF. Hearing aid designs deliver gain in increasing steps depending on the severity of the patient's hearing loss; the range spans from 10 to 65 dB of gain. To prevent feedback with the highest amounts of gain, such
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including reverberation and echo, and the relative positions of the microphones, the loudspeakers, the sound sources and the audience. Each doubling of the number of open microphones (NOM) reduces the PAG by 3 dB.
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A hearing aid incorporates a miniature microphone and a very small speaker driver, and various conditions may increase or decrease the amount of gain that can be applied to the microphone
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to change the frequency response of a microphone or loudspeakers system to increase GBF. The frequency which first begins ringing or feeding back is identified by the operator, and a
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The distance from the sound source to the microphone is a critical element of GBF. Greater GBF is obtained with the performer closer to the microphone; an instance of the
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is engaged to reduce the overall level of that frequency. This process is repeated several times to identify and reduce the level of further feedback frequencies. A
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Every time the number of microphones doubles, the
Potential Acoustic Gain of the sound system decreases by 3 dB.
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automate and speed the process of identifying and reducing feedback frequencies. A small amount of
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designs require the tightest-fitting earmolds with no venting, and the deepest penetration of the
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before feedback. A well-fitted hearing aid has more GBF than one that is loose. The shape of the
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Directional microphones are used in live sound to maximize GBF. Directional microphones with
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applied to the signal can increase GBF, as can the addition of a few milliseconds of
318:. Recording and Audio Technology (2 ed.). Hal Leonard Corporation. p. 52.
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103:(stage wedges). Directional loudspeaker systems may also be used to increase GBF.
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can be used for the same purpose but with somewhat less precision. Automatic
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re-enters the microphone and the system begins to ring or feed back.
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How much a microphone can be amplified before causing audio feedback
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341:"Lose The Feedback: Improving Gain Before Feedback in Worship"
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to place the speaker driver as close as practical to the
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at or just below the point at which the sound from the
437:. Dr. Carl R. "Rod" Nave, Georgia State University.
371:"Understanding Acoustic Feedback & Suppressors"
407:Hearing aids: standards, options, and limitations
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201:"Microphone Techniques: Live Sound Reinforcement"
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214:. December 2007. p. 36. Archived from
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62:performance. In both fields the amount of
410:(2 ed.). Thieme. pp. 242–243.
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42:) is a practical measure of how much a
435:HyperPhysics: Potential Acoustic Gain
241:"How-to: Miking Acoustic Instruments"
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284:"Increasing Potential Acoustic Gain"
312:Gary D. Davis; Ralph Jones (1989).
339:Hargraves, Kent (April 28, 2011).
113:The sound system operator can use
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245:Shure Notes for Houses of Worship
315:The sound reinforcement handbook
176:Control Theory § Stability
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369:Troxel, Dana (October 2005).
208:Shure Educational Publication
456:Sound production technology
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48:sound reinforcement system
404:Valente, Michael (2002).
292:Georgia State University
76:Potential acoustic gain
18:Potential acoustic gain
58:, GBF is a measure of
46:can be amplified in a
282:Nave, Carl R. "Rod".
131:feedback suppressors
36:gain before feedback
461:Tone, EQ and filter
108:inverse-square law
451:Audio engineering
127:graphic equalizer
123:parametric filter
101:foldback monitors
32:live sound mixing
16:(Redirected from
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115:equalization
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99:presence of
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145:Hearing aid
135:pitch shift
60:hearing aid
445:Categories
182:References
86:Live sound
44:microphone
345:StudyHall
160:ear canal
56:audiology
375:RaneNote
170:See also
96:cardioid
68:decibels
164:eardrum
155:earmold
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389:May 2,
351:May 2,
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297:May 2,
259:May 2,
225:May 2,
151:signal
249:Shure
219:(PDF)
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119:notch
54:. In
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64:gain
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80:PAG
40:GBF
30:In
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