By default, a Debian Wheezy system, when not in graphical mode, will beep on terminal input errors, like pressing backspace when there isn't any character to erase, etc.
In this page, we will describe how to disable those sounds.
Disabling the beeps
The way that works for me in Debian Wheezy is going to alsamixer and muting (pressing the m key) the beep column.
It is very important to mute the volume and not simply lower it because the beep is still active, even with the volume set to 0.