An interesting idea, but that kind of mixing requires a nonlinear element somewhere. Otherwise the resulting signal is just an independent superposition of bot

An interesting idea, but that kind of mixing requires a nonlinear element somewhere. Otherwise the resulting signal is just an independent superposition of both waveforms with no new frequency components. (Think about what a colony of bats would sound like to us, if that weren't the case.) Given a high enough sound pressure level, your own eardrums might end up providing the required nonlinearity. The warranty sure sucks, though.