First time I noticed it was this morning at the kitchen sink doing some dishes. Turned it off and the noise stopped. Turned it back on and there was no noise. Second occurrence was about 10 minutes ago when my wife turned on the washer. Had her turn it off. Waited a couple seconds then ran hot water in the kitchen and started the dishwasher. No noise. Had her turn the washer back on. No noise.
Pressure valve was replaced just a few years ago. No problems with toilet flappers that I’ve found.