I've written a lot on the hum, seeing that it is closely related to earthquake effects. These people are located on a 'drumming sediment', which resonates exactly with the frequency of the mysterious steel plant in Michigan.
This is rich, considering that Michigan is always bitching about our nuclear waste in the world's worst rock.
There is probably no resolution to this issue. Wait until these guys get a real earthquake! They really need a seismic noise test done by someone with brains.