Automuter

From Automuter:

How to turn off computer sounds in a graceful way? For those people who don't like to left music playing and lock PC disturbing colleagues with annoying sounds from headphones we've developed our new program. Set up your own rules of turning off speakers/headphones or do it with a hotkey! Automuter is an application that stays in system tray notification area (near windows clock). It can mute speakers when computer is locked, when screensaver is running. Alternatively, you can set up you own silent time schedule or mute by hotkey.