By default, in Debian Wheezy, while not in graphical mode, will beep on terminal input errors, like pressing backspace when there aren't characters to erase, etc.

In this page, we will describe how to make disable those sounds

Disable beeps

The way that works for me in Debian wheezy is going to alsamixer, and mutting (mute pressing m key) the beep column.

It is very important you mute and not lower the volume because, thought at volume level 0, the beep is still active.