Are bearing seats the same as the bearing race?

 

The area in the hub that the race is tapped/pounded/pressed in to is what I meant.  The hub can get worn out.  Probably from running worn out bearings which allow things to gain speed from side to side.  Many tiny impacts.

So he may need a new hub.

Thank you, some good ideas. I'll try the shake test. I'd think a bad hub would be a more continuous noise but maybe not. Brakes were grinding because a pad or pads were worn out. Maybe the pads went out after 15K miles due to lots of stop and go driving. 

Had to go to a job in Bellflower today, about 20 miles on the surface and 50 on the freeway, round trip. It did the ratchet sound after about 2 blocks, again after 10 minutes, and that was it, nothing the rest of the way and back. So it happens maybe once every 100 applications of the brakes. The brakes work well, no pulling to  one side, usually no noise. I may have heard it once more, back in town, but much quieter, could have been another car. It happens during applying the brakes, mostly at low speed it seems. As you slow down the clicks slow down. I stopped by the mechanic's, he thinks a pad is sticking occasionally due to a slightly warped rotor. He doesn't think it's serious but I don't like it. Maybe I'll install new rotors when I get paid. I had a sticking caliper (different sound, intermittent but not clicking as I recall) the previous time, and replaced them.

 

The other frequent little squeaking sounds have gone away since installing new bearings last week. It's probably OK to rule out anything that would require a coincidence. The ratchet sound is exactly the same with the old and new bearings. It didn't do it before they put the new brakes, instead there was the usual low-pitched grinding sound every time the brakes were applied.

Found the receipt from the brake job couple months ago, they put pads/shoes all around but only turned the right rotor. Guess the left one looked OK. Maybe that's it.