[iotscale]

You most probably have some "coil whine"[1]. It's very unlikely that you are hearing ultrasonic signals (disclaimer: I'm no expert).

[1]: https://en.wikipedia.org/wiki/Coil_noise

[mSparks]

sounded like "coil wine".

doesnt stop a phone app decoding it though. it was only when i moved the mouse. and came then went.

And i definately still have reasonable high frequency hearing. for example filing a complaint with Morisons in the UK for those high frequency speakers aimed at stoppping kids loitering. Don't know if they got rid of them or not because i stopped shopping there.