"pwip" noise at startup? (just curious)

[beefinator]

First off, I don't think this is actually an issue, so I'm not concerned about it, just curious.

When I turn on my minibrute, I can hear a very faint high pitched "pwip" noise.
The thing is, it's not out of the audio output!
It is producing an audible sound, which I can hear if I put my ear next to it.  It might be coming from towards the upper right quadrant of the controls panel, but I don't know.

What might cause this sort of sound in an electrical circuit that is presumably solid-state?

[Bruno@arturia]

that's the power supplies startup. during first stage only very low current is drown. during second stage(normal mode) current is much higher. the inductor is "singing" under low current, but has quiet when current settles. it's normal.
You may experience it too with wall adapter when no load is connected.

[beefinator]

That makes sense, hadn't thought of the inductors.  True, they're basically like really really crappy speakers, coils of wire that it would be impractical to try to stop them from moving at all.