Did the XF-84H Thunderscreech really cause "900 sonic booms per minute"?
I think it is a matter of where you stand (literally).

From the front or the rear the shock waves from the propeller tips would hit your ears continuously, and the result would be constant noise.

When standing laterally, the propeller tips would move towards and away from you and produce a variation of noise intensity of the frequency produced by the product of propeller RPM and blade count.

It seems that the design RPM of the XF-84H propeller was 3000, and since the propeller had three blades, the frequency should have been 9000 per minute, not 900. The airframe could be split ahead of the cockpit to allow the installation of several nose sections with their own gearbox and propeller. Several gearboxes and propellers were prepared with propeller design speeds between 2100 RPM and 3000 RPM, but the test program was ended prematurely, so most of the planned variations were never flown.

I can only judge from the little information available online and count myself lucky not to have witnessed a power-up of the XF-84H (for me personally, the loudest aircraft is still a Sukhoi 22M-4 &ndash; you think "man, this afterburner is loud!" and only then the pilot switches the afterburner on), and it seems that the 900 per minute figure must have lost a zero on its way of becoming an internet meme.

Note that I only speak of a variation of noise &ndash; as Jon Story writes, a sonic boom is what arrives at your ear, not what is produced by the propeller.