Anyone have an idea about unidentified constant noise/vibration in single-family house?
Throwing the main breaker on your electric panel is easy; you should try that. If cutting the power to the whole house stops the problem, then turn the power back on and start turning off circuits one-by-one. Hopefully they're labeled so you can identify the appliance or room, but this may take some trial-and-error.

Here are some other possibilities I can think of:


Pump for well water (if you have it).
Some other vibration coming in via municipal water line (although I can't imagine what would cause repetitive vibrations from a water main). If you do get water from your city/town, try to find the main service entrance and put your hand on it, to see if the pipe is vibrating.
An exhaust fan: maybe in your attic?
Radon mitigation fan (these typically run 24/7, drawing air out of your basement/crawlspace, through a duct).