Automixer

An automixer, or automatic microphone mixer, is a live sound mixing device that automatically reduces the strength of a microphone's audio signal when it is not being used. Automixers lower the hiss, rumble, reverberation and other extraneous noise that occur when several microphones operate simultaneously. They may also be used to mix sound from non-microphone signals such as playback devices.

Automixers are typically used to mix panel discussions on television talk shows and at conferences and seminars. They can also be used to mix actors' wireless microphones in theater productions and musicals. Automixers are frequently employed in settings where it is expected that a live sound operator will be not present, such as courtrooms and city council chambers.

Automixer hardware or software uses a variety of methods that allow increased gain before feedback for live sound reinforcement as well as reducing comb filtering between multiple microphones for recorded and broadcast applications.

Automixers balance multiple sound sources based on each source's level, quickly and dramatically adjusting the various signal levels automatically. Automixers are used in live sound reinforcement to maintain a steady limit on the overall signal level of the microphones; if a public address system is set up so that one microphone will not feed back, then, in general, multiple microphones will not feed back if they are automixed. The equivalent number of open mics (NOM) present at the output of the automixer is kept low, regardless of the actual number of open mics.

While a skilled audio mix operator can greatly enhance the performance of a sound reinforcement system he cannot anticipate with perfect accuracy which participant will speak next in a spontaneous discussion. Sudden interjections by panelists may be lost completely, or the beginning of a word may be absent (or upcut) because the operator does not respond quickly enough to "fade up" an audio signal. A properly adjusted automixer can prevent losing words or phrases due to upcut mistakes or lapses of attention.

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