are a bit different from the other AS dinnettes, as the seating surface stands proud (or away) from the vertical support. How does the table rest on it when in the bed position? In the other AS dinettes, I've seen a small wooden cleat that holds the table flush with the seating area to make the bed. I don't see that cleat in any of the pics.
I'm betting that the subwoofer is getting sine wave interference from the electrical supply (probably 60 hz). I think there may be some sort of resistor that you could put in line to eliminate it.