Here's another perspective, from someone who owns similar technology HVAC equipment - mine is also GSHP equipment, though manufactured by WaterFurnace instead of ClimateMaster.
In my case, I too have a "humming" noise level that at times can be bordering on annoying. This was a concern throughout installation. While the GSHP installer did a number of things to reduce the humming, it didn't get eliminated by any means.
The situation with a lot of GSHP equipment, like mine, is that the compressor is part of the packaged unit. Water loop heat exchanger, air loop evaporator heat exchanger, compressor, and blower motor are all key parts of a single 'box.'
The obvious advantage is that there's no equipment outside to deteriorate from the elements. The less obvious detraction is that you now have a compressor, with associated noise, inside the house.
In my case, the GSHP units are in the attic. Mine are installed via suspension from the roof rafters, versus being installed by sitting on a deck on the attic floor (ceiling joists), in full attempt to lesson vibration 'hum' transmission from the compressor to the house.
And another noise reduction technique was to use flex duct for the last 6' of connection from the steel rigid duct to the ceiling supply/return registers.
Still, the compressor 'hum' is noticeable.
I remain convinced that the economics of geothermal HVAC is 'the real deal.' But, it isn't perfect, and among the drawbacks I include is noticeable hum from the compressor.
Perhaps this is in fact the challenge. If so, then it's going to be a tough problem to solve.
(Below is an image of how my units are suspended from the roof.)
I really appreciate your perspective. The humming occurs while the compressor is not running, as well (that is, when only the FAN is running).
After removing one of the side panels to adjust the fan speed, I noticed that the hum had gone down considerably. So, I've just decided to leave the side panel off. Does anyone advise against this?