Ive been following the letters concerning helicopter noise while on vacation. From the foot of Bishops Peak, we noticed what sounded like much louder helicopters operating around the peak than usual. Almost daily, I spotted a V-22 Osprey operating in the area, usually to the north of Bishop Peak.
The Osprey is technically a tiltrotor aircraft, functioning as an airplane with the rotors tilted forward and as a helicopter when the rotors are tilted up.
As far as I know, the Marines and Air Force have the only operational Osprey squadrons. We were more interested than annoyed by the Osprey, as we have become so used to helicopters plucking fallen hikers from Bishops Peak on a regular basis the last couple of years, but yes, the Osprey is way louder than most helicopters.