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Collaboration, Voice & AV · Intermediate

Automatic Mixer (Automixer)

A mixer that automatically turns up active microphones and attenuates inactive ones to reduce noise and feedback.

Definition

Gated automixers open and close channels based on thresholds, while gain-sharing automixers distribute a constant total gain among channels in proportion to their levels. Limiting the number of open microphones (NOM) matters because each doubling of open microphones reduces potential gain before feedback by about 3 dB. Automixers are standard in conferencing DSPs.

Example

With twelve ceiling mics, the gain-sharing automixer keeps total gain constant as different people talk.

Exam tip

NOM attenuation: each doubling of open mics costs about 3 dB of gain before feedback.

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