Is this a bad crank bearing?
 

Girlfriends sons Explorer us making this noise. It happens under power with a load but doesn't stop immediately when you let off. Does it sound like a crank bearing? Power seems fine, just the noise.

https://youtu.be/Pz7BOCB_mC0

will it make the sound while standing still in neutral?
Will the sound continue if you put it in neutral while moving?
will the frequency change with rpm or speed?
hard to tell but bearing in alternator or idler would be a place to look.

That's not anything internal. My guess is belt tensioner.

That video really shows is the best it could. Basically to reproduce (reliably) I can just give it 50% throttle for a couple seconds. While it's under load the noise will start and keep going for ... uh, about as long as it did in the video after letting off the throttle.

- It doesn't happen in neutral without any load
- Frequency doesn't change with engine or car speed

I'll pull the stethoscope out and check all the pulleys whenever he finally comes out. I'm not sweating it too much. Thanks for the input!