Howling siren sound when shower or toilet is flushed

[Titan7]

Not sure this the right forum but in the house we just purchased, 2017 build, we noticed that there is a siren like sound when the upstairs or downstairs showers or any of the the toilets are flushed. the sound comes from the water main where the supply enters the house. I can also feel the pipe vibrating a little. Water pressure is around 69psi. Thinking it could be the diaphragm in the water pressure reducing valve or ?.
thank you

 

[Reach4]

Try changing the setpoint of the PRV (pressure reducing valve) up or down. That may work around the problem.