FBI could force us to turn on iPhone cameras and microphones, says Apple (theguardian.com)

Simple covers for laptop cameras are sold. I wonder, could similar simple and cheap product be made to baffle a microphone?

I'm thinking, without much knowledge or sound or microelectronics, a white-noise generator that would be situated next to the microphone, so that noise would be drowned out.

Or maybe even a simple sliding cover for it.