If may be the hEX, but see this thread beeps every 30 seconds.
You may want to place a microphone close to it and record it with something like audacity so you can verify that it is truely the hex, and not something else. And you could then look for the duration between the beeps too.
Hopefully you aren’t being pranked by something like this Sneaky Beeper
But I’m sure @rextended could code up a script for the hex.