Humans are not perfect sensors; there are changes we are sensitive to and changes we are not. As a trivial example, if a speech synthesis system was emitting h

Humans are not perfect sensors; there are changes we are sensitive to and changes we are not. As a trivial example, if a speech synthesis system was emitting high frequency static, we wouldn't hear it at all, but would be trivial to detect with a microphone. I fully expect software to be better at this than we are if there ever turns out to be a need for this sort of thing.