Given that they were only authorized to fly in the "Bell X-1 supersonic corridor", I'd wager that sonic booms are fairly commonplace there. I doubt there are any residents around.
There are residents for sure in that corridor, but the residents are on Edwards AFB, and are fairly used to sonic booms. When I was on Edwards, there was still the last operating SR-71, and that boomed any time it flew.
https://www.afmc.af.mil/News/Photos/igphoto/2003098938/