My neighbor had his TRANE heat pump serviced over a year ago. Ever since I can hear the heat pump humming LOUDLY through out my home. The entire SFH. I am in a community where the houses are closer together than normal, but for the first *two* years it was quiet.

I have to keep a tv or fan on to block it out. You can hear it in every room. Needless to say, he says he will do something about it, if I pay for it. What could it be? Loose metal or what? Please help!!!!