Guest
Noise often comes from valve seat parts vibrating as the seat gets close to closing as the water is opened or(more often) closed. The high velocity water makes a vibration as it goes past the narrowed path, somewhat like air over a wing at the speed of sound.
You want to find the offending valve or other cause at its location and change the cause. Sometimes toilet valves, pressure reducers or single-handle valve parts offend as the pressure changes. The sound needs to be localized by using each valve while listening. An experienced plumber could take less time as he probably has solved these sounds several times.
