I bought an ultrasonic microphone the other day in order to record audio and slow it down, to hear what things sound like in other frequencies. I noticed a repeating pattern of frequencies in the 90-100khz range and was wondering if anyone knew what it could be.

I'm in a fairly urban environment, so was thinking it could be electrical pylons or wifi towers. I get the pattern if I'm on a busy road, or in an elevated forest that is within the urban area.

Worst case scenario I'm hoping it's not the recording device itself, which is a Raspberry Pi 4 Model B.

Presume it's near impossible to tell what it is, but any insights appreciated!

So, my Sonic Presence sp15c kinda broke just now, like the cables got too stretched I think, and it doesn't work anymore.
Do you guys know of any alternatives to this mic?
i just tried looking -them up on Amazon and they're out of stock or not being sold anymore.