barath_s t1_iryxkfd wrote on October 12, 2022 at 1:53 AM

Reply to comment by Zebidee in TIL that passenger jet engines produce most of their thrust from fan at the front, not from the jet exhaust, and that this is called a high-bypass engine. by Rilot

Probably talking about turboprops where the prop tips are supersonic. These tend to be noisy.

Such as the Tu-95 and XF-84 Thunderscreech

> the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run. Coupled with the already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews. In one report, a Republic engineer suffered a seizure after close range exposure to the shock waves emanating from a powered-up XF-84H

also wiki for Tu-95

> The Tu-95 is one of the loudest military aircraft, particularly because the tips of the propeller blades move faster than the speed of sound.

Note that turbofan tips for modern engines may also be supersonic