Well of course, the first question is, why would you be turning the auto-fill off? Makes not sense as it's designed to be on at all times. The only time I've ever seen one turned off is when it's defective and over filling the system and HO is too cheap to change it out. An auto-fill valve operates on differential pressure. When you turn it off, the pressure between the shut-off valve and the auto-fill valve will reduce to boiler system pressure if the auto-fill were to try and open due to low system pressure. When you turn the auto-fill back on, it has to put a little water into the system and then allow the street pressure to build in the supply line. Leave it turned on and you won't hear that noise. Like the guy who goes to the Dr. and complains of a pain in his arm ever time he does one-armed pull-ups. The solution is to stop doing one-armed pull-ups!
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!