First of all, we can rule out water hammer because water hammer only occurs as a result of the rapid rise from dynamic head pressure (working pressure under flow) to the static head pressure (pressure when there is no flow).

The type of noise your describing is a constant chattering noise that occurs during the flow. It generally is a result of a rapid fluctuation in pressure caused by a loose valve seat that is rapidly fluctuating, such as a loose faucett washer, defective solenoid valve or a weakened spring in a pressure regulating valve. This type of noise is generally most pronounced in the near proximity of the source, which in your case is at the Pressure Reducing Valve.

Pressure reducing valves are factory preset to allow the code maximum of 80psi, however a PRV regulates the pressure by means of a spring activated diaphram and in the course of time the springs can and do weaken.

The proper fix is to replace a defective PRV, however you may be able effect a temporary repair by slightly increasing the tension of the spring. On the top of the PRV you will see what looks like a bolt protruding out of the top of a round dome. You may try turning that bolt ONE TURN clockwise, and that should relieve the problem, but absolutely DO NOT turn that bolt more than one turn. Doing so could cause the PRV to allow pressures in excess of your plumbing design range and could cause damage to both pipes and fixtures throughout the house.

If turning that bolt one turn does not resolve the problem then you will need to replace the PRV.

Thanks lazypup, that makes a lot of sense.

I did fail to mention that I bought a water pressure gauge to measure a 60psi in the house. I assumed that if the psi in the house was acceptable, then the PRV was working OK. What you are saying is that there may be damaged by a valve seat, but it continues to manage waterpressure?

This would make sense to me, but I want to make sure that my understanding is correct.

Cheers.