The problem is - lots of things create infrasound. This is the loudest thing within that hour, and approximately the right time, but is it a sonic boom?

Sonic booms should have an N-shaped profile, as shown in this figure from their wikipedia article: https://commons.wikimedia.org/wiki/File:N-wave.png#/media/File:N-wave.png

That figure shows the whole thing lasting ~.2s.

If we zoom in on my own data, you have to stretch a little bit to believe that it has the same N-shape, but it's not entirely wrong.

The initial peak is ~.1s, but the whole thing takes ~.6s (from 21:42:26.4 to 21:42:27)

It was certainly one of the loudest things today, and a broad-spectrum 'boom'.

(Ignore the really huge thing in the recent lower left, that was me rebooting the RaspberryBoom because I thought it was offline 😬)

The big thing in the quiet nighttime hours is a helicopter - those have a very distinct signature.

@grajohnt
Sue has become very good at distinguishing the local police helicopter and the air ambulance helicopter just by their sound as they become audible.

Seeing the hospital helipad light up is a good confirmation of an incoming air ambulance.