Why is it that your own voice sounds strange to you when you hear it played back on a tape recorder,

Why is it that your own voice sounds strange to you when you hear it played back on a tape recorder,

Why is it that your own voice sounds strange to you when you hear it played back on a tape recorder, but your friends all agree that it is just what your voice sounds like? [ Hint: Consider the media through which the sound wavetravels when you usually hear your own voice.]