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.
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).