The Republic XF-84H, known as the "Thunderscreech" was an experimental version of the F-84F Thunderstreak. It was intended to be a supersonic turboprop fighter. Even at idle, the prop tips rotated at supersonic speeds and the plane is often claimed to be the loudest ever built, supposedly audible 25 miles away.
Most sources describe a continuous sonic boom due to the supersonic prop tips. However, a fairly common claim on the internet is that they caused "900 sonic booms per minute."
Is there any truth to the claim that the plane caused 900 sonic booms per minute?
One's first thought should be, "no": because the prop tips are continuously above the speed of sound, they emit a continuous sonic boom (as most sources claim), not 900 separate ones per minute. However, since the prop tips were supersonic and the roots were not, it follows that a section of the prop's length would be in the transonic range. Any change to the wind or propeller RPM would cause more or less of the propeller to be moving supersonically. I suppose that, say, an appropriate oscillation in the turbine engine could cause the continuous boom to be modulated by some 15Hz (900-per-minute) component.