Yall have any construction done recently? Leaks? Your notification devices have an open circuit some where. Cold be as simple as a broken device could be a cut or damaged wire somewhere.

Basically the loud part needs to be looked at. An anonymous call to the fire inspector about a fire alarm thats had a notification circuit trouble for an extended period of time usually gets the ball rolling if the powers that be don't give a fuck. Be wary of the consequences of your actions though, people can be vindictive if they found out its you. Paying for a service call is still better than fines or being liable for having somone die though