opaqueice Wrote: > 3) there is no distortion, so the speaker cone's motion is symmetrical > but reversed in phase. The sound waves produced differ only by a > "polarity reversal", and the human ear+brain can distinguish the > compression versus rarefaction type waves. However I'm not sure this > possibility makes sense, because it's not clear to me a real sound wave > in air can behave that way, since I think compression must always be > followed by rarefaction, and the other way too. On average the > pressure probably has to stay fixed to the room pressure, otherwise it > seems there'd be a net flow of air towards or away from the speakers.I don't > think you have said this quite right. The cone moves forward and backward, and the pressure indeed varies around the atmospheric pressure: compression is followed by rarefaction. Even if the backward motion were only back to the neutral position (which, as you say, would be a DC offset, which you have removed, so it isn't), it's still moving back. It just moves back differently than it moved forward: ideally, fast with a sudden stop, as opposed to the smooth turnaround through zero velocity at the forward end.
Of course, you have suggested in other posts that physical objects don't really move like that, and I agree: the cone, the air and your ear are all going to make the wave more nearly harmonic because that's how they all like to oscillate. It will still be asymmetrical, though, and I don't find it implausible that the asymmetry will be perceptible. I also don't find it all that farfetched that asymmetrical transients play a role in people's perceptions of "musical" material, even though you are quite right that most instruments spend most of their time in harmonic motion that is essentially steady over much longer times than the period of the sound waves. What is interesting to me is your description of your perception, particularly the part about pitch. Now, a very simple experiment will serve somewhat to distinguish different phenomena: move. What happens if you sit behind the speaker? If the speaker is faithfully reproducing asymmetric waves, you might hear something more like the opposite wave from in front. If, on the other hand, the speaker (or, rather less likely I think, the electronics) is distorting the two signals differently, it may not make much difference where you sit. By the way, I believe most people perceive a remarkable change in sound from a sine wave played by a single speaker in an ordinary room, just by turning their heads. -- tom permutt ------------------------------------------------------------------------ tom permutt's Profile: http://forums.slimdevices.com/member.php?userid=1893 View this thread: http://forums.slimdevices.com/showthread.php?t=23759 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
