If you mean gain as in mixer input channel gain/trim, no auto control that I know of.
In general I’m not sure I would want auto input gain staging on a mixer, with some inputs you would be chasing after the level changes / dynamic range that was intended from an instrument or vocalist. If there was such a thing I would want to be able to turn it off.
In the case of soft spoken speaker something automatically adding a lot gain could lead
to feedback issues, any sound system will feedback is enough gain is applied to it.
As Showtime said compression will help tame the loud talker but that is taking place
after the channel input gain.
And as mentioned a skilled audio engineer with hands on faders and knobs. More than
once I’ve had my hands on the channel gain and fader at the same time during shared mic
speaking events or for the times when the person speaking is all over the place in there
speaking level.
Keep in mind if this is wireless mic you need to find a mid way transmitter gain level
that will work for most people speaking generally based on what the loudest mic input will be. Some new digital wireless mics have a very wide input level range so transmitter gain is less of an issue.
