Customer has couple of old Bogen horns in a mechanics shop. Amp is a TPU-35A. There is a WMT-1A matching transformer between amp and phone system (Avaya BCM50).

During a page, you hear the audio, but also some noise. Customer described it a being under water. To me, it sounds like the amp might be overdriving the horns. Settings are the same as always. I even turned down the main volume control. Without a page, you can hear a slight hum. Could it be wiring that is common to both horns? I don't have a spare amp to try. I'll have to listen to the output of the phone system with a butt set to see what that sounds like. I think those amps are generally pretty solid.

Thanks.
Jim