[drdaeman]

Not as long as it cuts the wire that breaks all connections between board and the microphone(s) (and board is somehow audited to not contain any extra microphones or otherwise sound-sensitive components).

<tinfoil hat on>But this is only as long as you actually can verify or trust that the switch is actually a switch and not a device that pretends to be one. A transparent casing where one can visibly confirm the actuator operation is a good idea.</tinfoil hat off>

[SAI_Peregrinus]

If you want extra tinfoil hattiness, most multilayer ceramic capacitors (the surface mount kind that are everywhere on PCBs) are somewhat microphonic. Condenser microphones, especially electrets are basically just capacitors designed in a special way to maximize this effect.

[drdaeman]

Interesting! I know about condenser mics, but I thought a typical SMDs are way too small to sense anything useful. Had anyone experimented with this?

[SAI_Peregrinus]

They generally are too small to be useful. That's why I called it "tinfoil hatty". Most of the issues with them come from mechanically coupled vibrations in a system (from fans and the like) flexing the whole circuit board, so it's not as big an issue with phones. Also most of the capacitors are power supply decoupling caps, so difficult to sense variations from.

It's mostly just a fiendishly annoying effect in high-sensitivity test equipment.

[6d6b73]

The problem with that is that you can turn speaker info a microphone:)

[drdaeman]

True, but a multi-pole switch can also cut connection to those.