idleSound
Automatically mute your Mac when it becomes idle or your screen locks. Idle time as well as the screen-lock/screen-saver are individually adjustable.
Download
You can download the app here, or get the source from GitHub and build it yourself.
Screenshot
Features and Settings
You can set the idle time after which the Mac should be muted further you can chose whether the Mac should be muted when the screens turn off or the screen-saver starts. Both settings can be disabled through the menu bar. More information can be found in the “about” dialog box which is accessible through the menu-bar.
Known “issues”
Doesn’t work well together with Caffeine this is because Caffeine fakes user activity instead of doing it the right way and setting hooks in the system. A tool that sets system hooks instead of faking user activity are Amphetamine (iTunes link) or iCanSleep.
License
Licensed under the terms of the GNU General Public License version 3.