MacBook Pro 15" 2018 makes jackhammer noise on speaker

I have a 2018 MacBook Pro, 15", that yesterday started making a jackhammer noise on the speaker. I am using Mojave 10.14.6. The noise is not all the time, but seems to happen sometimes when I transition between windows, or even tabs on my browser page. It doesn't seem to matter whether I have numerous windows open, or just one, or just my home screen and no windows. I'm not sure exactly what starts/causes it. Sometimes closing the window I'm in will stop it. Sometimes I have to restart. Sometimes I have to restart a second time.

This has become a nuisance. I have not been successful in trying Diagnostics, probably because I'm not sure what I'm doing.

Have you heard of this problem? If so, is there a fix?

I hate that, once again, I'm having a Mac issue within a couple of years of purchase of a very expensive computer. If there is not a free fix or an inexpensive one, this will likely be my last Mac after only purchasing Macs since 1984.