Suppose we are travelling supersonic along a straight line. Further up along the line, there is a stereo, that's emitting sound at a frequency that changes in such a way that the Doppler shift caused by our supersonic travel in relation to the stereo effectively cancels out, and the sound is hence always maintained in our hearing range..
If the stereo is loud enough will we (no matter how ever briefly) be able to hear the sound at all?