Strange Noise Under Floor

Sounds can travel in odd ways through buildings depending on a variety of resonant materals and spaces (and the combination of them). My suggestion would be to listen to the house itself by putting your ear on a solid material (like a wall or a floor), and follow the sound to the source as the volume increases. Take a variety of readings (several dozen) in one area to get a better idea of what's going on, and increase your data sample.

For more sensitivity, use a mechanic's stethoscope or an inverted drinking glass.

My guess would be a forgotten sump pump that is buried somewhere under there.

Jon

Now you know why it's called a crawl space. Get a good flashlight and happy hunting. If you see glowing eyes looking at you while under there it's probably not a good thing.

There is some ghoul living in there.

while the noise is occuring turn off the main breaker........

if the noise stops try isolating the noise to a single breaker...

if the noise does not stop then it might be a animal living under your home.

either way this diagnoses whats going on..

use care if its a animal

Clicks and motor sounds usually come from insects. Such souonds can be quite loud (think crickets). Looks for something small under there.

TKM

If all else fails, call Ghost busters.

Does it happen when you have the heat on? Could be the pipes expanding which is normal.