If this is in a US location, [strike]53[/strike] 63 Hz. sounds suspiciously close to 60Hz, our nominal AC line frequency. Air handling equipment, air conditioning compressors, large motors of that sort often are improperly mounted on hard fixed mounts and transmit large amounts of very low frequency noise that way. "Proper" mounting is on rubber sound isolators when noise is a concern, but I doubt the business would retrofit that.
If they are being co-operative, you might start wandering around their mechanical floors and equipment, testing for the same noise pattern. But tracking down anything at nearly subsonic frequencies can be a long and difficult process. Most equipment isn't really set up to deal with frequencies that low, and many people physically can't hear that low.
You might also try putting a frequency counter on your AC line, and theirs, to see if it comes up with the same odd 63 Hz. I don't know if "bad utility power" at 63 instead of 60 might be causing a problem but that's worth finding out. The local utility company should be able to check the powerline frequency for you--although they often stonewall on any "quality" complaints.
Sadly, the only practical way to get quiet may be to soundproof the bedroom, which can mean essentially building an isolated "room within a room". But that WILL solve the problem. (And if the problem is from that business, that solution still might be cheaper to them, than fixing an equipment problem.)
Last edited by hellosailor
on Tue Apr 22, 2014 6:14 pm, edited 3 times in total.