If I'm listening to something in Pandora or YouTube, and I'm in Terminal.app in OS X 10.7.5, if I use the up arrow to scroll through bash command history, then that works fine with no noises. But, if I scroll down past the last command in bash history with the down key, it makes a noise (somewhat the noise that is made when plugging an instrument cable into an amplifier). I've also noticed that some other actions will cause a similar noise, but I don't remember what they are at the moment.
Any idea what is causing this or if there is a fix?