Laser resonates with ceiling speaker to create a horrible ?ground loop?

[DonKu]

Received a phone call from a client in regards to a new medical laser device. Whenever the laser is activated it causes a sympathetic loud hum in only one of the Valcom ceiling speakers - located relatively far away in the waiting room. Speakers closer to the laser show no symptoms.

Haven't gone on-site yet. AFAIR, a sheilded audio cable feeds the speakers, and a LM386 drives them. The built-in Valcom LM386 amp uses a couple of exposed spade terminators, spaced about an inch apart, to connect to the audio line.

Is it possible for the terminators to act as an antenna? Or, does this indicate a broken/incorrect ground?

Thanks in Advance.

OK. It turns out the Valcom system uses cheap twisted pair and not the shielded audio line imagined in my mind. So, the most likely culprit is a twisted pair paralleled with an electrical line in the ceiling. The Valcom speaker will be disconnected to solve the problem.