Wonder if he means it's a "hum"? I recently had a customer complain to me about a hum coming from their sound system - they use the rec room for band practise. My thoughts too were the dimmers. Also the owner has put compact fluorescents all throughout the house, so I suggested he try turning off anything with dimmers and compact fluorescents when they practise. I still haven't heard back from him, so I'm assuming that was the problem.
