Mom started hearing a noise in her head. Is this part of the progression and will the noise come and go?

Make a note what time these sounds and vibrations happen, and also note if the furnace is running, the air intake can be a bit noisy.... or if the refrigerator is running as I can hear the refrigerator vibrating the floor whenever I am in the basement.

Sometimes water being run for laundry or a shower could be hyper-sensitive to some people. Or if a plane or helicopter is going overhead.

Please call her MD immediately and report the change. He may want to see her.

It's difficult to say. I have always heard that any change in mental status should be reported to the doctor. That way, they can note her chart, check her for things like UTI, medication review, etc. Since some infections and medications can cause similar symptoms. After ruling out those things, I'd explore a geriatric psychiatrist, if ou have one available. These delusions, hallucinations, etc. can be very scary. If they are distressing her, I'd try to find her some relief.