I have to assume the transducer mounting method that you are using.
1) If you are using magnets, replace them with isolated magnets or put a thin sheet of plastic between the surface and the transducer magnet. This is an electric isolator.
2) If you are using studs, mica (insulating washers) and isolated studs are available.
3) If the temperature is not too high, then a layer of bees wax (or petroluem wax) on a ceramic plate may be enough to isolate the transducer.
4) At last resort, use a cheater plug at your 110 volt power source. i.e. disconnect the ground plug.
I don't get ground loops any more except when I use older equipment. Step 1 above usually works and allows you to see if the ground loop is originating at the transducer or somewhere else.
Mounting accessories are available from Bruel & Kjaer or any of the major transducer vendors.