Mac OSX microphone input volume level auto-adjusts - can it be disabled?

I've found this issue and various discussions online about this, but no obvious "just do this", so I'm wandering over here from ServerFault to ask this.

Is there a way to disable or hard-set the input level on a mic? In the Sound preferences on the Input tab if I click on the device and set a level and then start talking it picks up the sound and then start to auto-adjust the mic input level.

This causes issues when talking with someone on Lync/Skype/etc because one minute the sound is fine and then if you raise your voice for a second and then lower it back down (or shift around in your chair) the auto-adjust causes the other party to think your whispering or yelling.

I'd like to be able to disable the auto-adjust if possible. Yes/No?

NOTE: The issue is similar this one: iMac OSX 10.8.4 Volume adjusts by itself but rather on the input side and not the output side for me.

You can set it via the command line:

osascript -e "set volume input volume 100"

I have found that OSX Polycom RealPresence Desktop has a similar annoying "feature" that adjusts the mic input volume down, but never back up. My workaround is to have this line in my crontab:

# Check every minute for mic input < 100%; if it is, dial it up elegantly
* * * * * while (( `osascript -e "input volume of (get volume settings)"` < 100 )); do osascript -e "set volume input volume (input volume of (get volume settings) + 3)"; sleep 0.1; done;

The loops just makes the slider "slide" up over a second or so, rather then a hard volume jump.

Turns out that the auto-adjusting mic level was not MacOS, but rather Skype (Version 6.6.0.467). There is a check box in Skype Preferences to enable/disable it, and once I turned it off the level stays where I set it.

The problem is that, apparently, Skype's notion of auto adjusting the mic volume is simply to crank it up to max, no matter what -- even when no call is active. At around 90% the mic starts picking up background noise, probably the Mac disk or fan, and by 100% that background noise is overwhelming.

I found that on my MacBook Pro (c. 2008) the mic level at about 75% was good, and I also found it helpful to check the "Use ambient noise reduction" check box (just below the mic level slider in the System Preferences/Audio).

I think I've found the work-around for macOS. You can create an “Aggregate Device”, which works with a single mic (but won’t help with multiple input sources) The Aggregate Device doesn't have its own volume setting, so GoTo can't mess with it.

Open “Audio MIDI Setup”. You can quickly find this by hitting Command+Space, then type in MIDI. Add “Aggregate Device”. In the left column at the bottom, hit the + sign and "Create Aggregate Device" Click on the new Aggregate Device in the left column, and check 'Use' for your microphone in the right-hand panel.

Now the Aggregate Device should be avialable as an input in GoTo. You can still set the sensitivity of the microphone within the Aggregate Device as you normally do, and GoTo can't affect it anymore because it is hidden in the Aggregate Device.

This won't work with multiple Mics in GoTo; GoTo only uses the first channel, so the additional channels are ignored. Rogue Amoeba Loopback can get around this by creating an aggregate device that only has a single channel, regardless of the number of inputs. It is really slick, and easier to use than Audio MIDI Setup, but costs $99.