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Automixer Using Audition CC 2014?

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Peter Jay GouldAutomixer Using Audition CC 2014?
by on Jan 5, 2015 at 6:01:50 pm

For those not familiar with a hardware automixer - it takes multiple microphone inputs and then mutes whatever microphones are not being spoken into. Very useful for panel discussions where everyone is wearing a lav and there isn't a live audio engineer to do a live mix. A decent automixer can differentiate easily between audio from a mic being worn by the person speaking, and spill coming from the mic worn by someone seated next to him/her. If multiple people speak simultaneously, an automixer can be preset to give certain mics precedence and mute the others or allow it to be a free-for-all (but reducing the overall mix to avoid overmodulating the final output).

I shoot panel discussions that are posted in Premiere, with anywhere from two to six participants, all mic'd and recorded ISO. The mix is done in post. So my question is: what (if any) tools are available either within Audition or as a plugin to approximate the same result as an automixer? We don't need any mics to have priority; just want to mute the mics whose wearers aren't talking and then bring them up when they say something without having to individually sculpt each track by hand (a two-hour panel discussion with six people takes quite a long time to do manually and I'm thinking there must be automation we can take advantage of).

Thanks in advance!

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Rob NeidigRe: Automixer Using Audition CC 2014?
by on Jan 6, 2015 at 3:59:55 pm

The function you are looking for in Audition is a Noise Gate. You set a threshold level. Any sound below that threshold and the gate stays closed, in other words the track is muted. Any sound above the threshold and the gate opens, allowing the sound to come through. You can also adjust how smoothly the gate opens and closes. It takes some tweaking to get it right without a "chattering" sound if the sound level is right at the threshold causing the gate to open and close rapidly back and forth. Like most things with audio, though, it's hard to just pick a "set and forget" level and expect to not have to tweak it in post.

have fun!


Rob Neidig
R&R Media Productions
Eugene, Oregon

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Peter Jay GouldRe: Automixer Using Audition CC 2014?
by on Jan 9, 2015 at 1:40:43 pm

Hi Rob,

An auto mixer is much more sophisticated than a noise gate in three important respects:
1) If no one is talking a noise gate would shut off all tracks, cutting out room tone. An auto mixer is smart enough to leave one channel on so there is continuous room tone and you don't hear the ambience cut in and out. Most common is "last mic on," i.e. the most recent active mic remains active until another one triggers.

2) If someone talks loudly enough to overcome the gate threshold on the mic worn by the person sitting next to them, intelligence in the auto mixer can differentiate between the higher quality sound reaching the speaker's mic and the more attenuated sound reaching the neighbor's mic, and keep the neighbor's mic muted while activating the speaker's. This is especially critical when someone with a naturally loud voice sits next to someone with a naturally much quieter voice, where normally they would constantly trip the gate on the neighbor's channel as well as their own.

3) If multiple people speak at once a good auto mixer will reduce the overall gain by a fixed amount depending on how many channels are open so the final output level does not clip. This is different from a compressor/limiter since it is not a continuous processing of audio throughout, but is based on reducing gain by a specific number of additional db for each additional channel open. Some auto mixers also allow one or more channels to be selected as a priority so in a free for all they will have more gain than the others so their audio remains intelligible in preference to the other multiple speaking voices.
So: an auto mixer plugin would reference multiple tracks simultaneously, since its intelligence depends on the interactivity between those tracks, while a noise gate operates independently on each channel without regard to what is going on in the other channels. Hopefully that makes sense.


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