One little known feature of linux is that there are ANSI sequences you can send to the console that turn off and off the PC buzzer and alter the frequency. One

One little known feature of linux is that there are ANSI sequences you can send to the console that turn off and off the PC buzzer and alter the frequency. One innocent use I used for this once was when I set up an on-demand modem system using ISDN for the office. If it detected a packet for off-site, it'd start the modem dialing and when the link was up, it'd make a series of ascending tones and after a minute or so of inactivity, it'd take down the link and play some descending tones. People tried not to use the internet unless they heard the ascending tones, so we only used a couple of hours of dial-up per day. One not so innocent use for this was trolling the phone engineers who were tasked with installing something in the rack in the corner of the office. Every time they went round the back of the rack and touched anything, I'd make one of the servers beep, but always a different one and only when they touched a wire. Occasionally I also ejected and then tried to mount the CDROM, so they'd just hear a thud every now and then too. They literally had no idea what was going on and got quite paranoid every time they went to touch anything.