Thanks, Paul.

My (vague) understanding is that, due to the way in which the electronics adjust the pitch, the sound emanating from the detector isn’t remotely like that made by the bats. But we can hear it, and that’s all that matters.

I can only interpret one of the sounds made by the bats… As I say in the extended version of my piece (above), bats vastly increase the click-rate when going for the kill. If you listen to my recording of bats within the piece, you can hear this happening at one point. It sound like a very high-pitched fart, as if something has gone wrong with the recording, but it always seems to happen as the bats suddenly jink sideways after an insect.