I had to do some repairs to my system, and just happened to be working in one of my valve boxes when I heard the valve open. There is no water pressure to this valve, so I didn’t worry about it. However the valve was making a pretty loud chattering sound (Hunter Valve). I then tried a few other valves in the system. They also were making noise, more of a buzzing sound, and quieter (Irritrol Valves), but they seem to open and operate the system normally. Is this normal, and I just never noticed it before, or do I have some sort of power issue?