Pressure vacuum breaker making noise

My PVB is making noise. It sounds like somone is using a weed wacker/trimmer. The noise goes away when I turn on my irrigation system. Any idea why all the sudden this noise started? Is the PVB bad, or is there some other problem?

Thanks, I appreciate any advice.

noise

Sounds like that are usually caused when your irrigation system has a small leak so that the PRV does not have to open completely to allow the flow.

Thanks for your response, I appreciate it.
I've only owned the house 6 months (the house and the irrigation system are 10 years old). I had an irrigation company come out and service the system earlier this summer prior to turning it on. Is springing a small leak common? I've only used the system 2 times this summer because we've had a fair amount of rain. Is there any way to determine where the leak is? And is this something I try to do myself?

Again, thanks for your thoughts.