You’re right: I’m making some naïve assumptions there. My suspicion that mobile phones microphones can’t handle high frequencies is based primarily on the fact that they can’t transmit them (as anybody who’s ever tried to listen to music over a mobile connection knows!), as I first discovered when, in 1999, I experimented with hooking up conventional acoustic coupler modems to GSM cellular telephones.

I’ve tried to test the other point you made, but sadly I’m unable to fit my head into my pocket. Even if I could, though, the test would be unfair: my mobile phone only has one microphone (whereas I have two ears) and it’s generally pressed against the inside of my pocket (and is therefore muffled by my leg, too: a lump of skin and fat that acts as a very effective sound suppressor).