Floor Makes Metal Clang When Walked On – One Room

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).

It's probably just the pipes expanding and contracting under temperature changes. They can bind on an anchorage, then suddenly break loose. The floor and pipes do reverberate, amplifying the sound. The tension release and sudden movement can be very small, yet the resulting sound rather startling.

If you can identify where the pipe is hanging up, you can replace the anchor with one that has a plastic liner that is resistant to binding. Or simply loosen the anchor or remove it, wrap the pipe with cloth tape, then reinstall the anchor.

It can be difficult to locate all the pops and creaks, they seem to come from nowhere sometimes. You should at least be able to quiet the worst offenders.