These are used by PC builders to diagnose power on, bios and motherboard issues via beep codes.

A must have for any serious builder!

General meaning from beeps are: (Please note, these can change depending on your setup - This is only a example guideline)

Continuous sound (long beeps): RAM is not seated or damaged. Re-insert, if that does not work, replace the memory.

If it keeps ringing: Check power supply, display and graphics card connected.

Check all plugs.