An earthquake is with me no beep emitted, but rather a vibration.
Since the mole Schreck is offered in the same design with vibration, I've assumed that an "earthquake" is generated by the vibration and not by a beeping ....
Will write in a few weeks if the beep part still works.
Advance from me only one star because you have not described it apparently targeted precisely that it only beeps and does not vibrate.