I've become curious about the claim that absolute polarity can be audible. I'm very skeptical that this is possible in music, but on the other hand it seems pretty clear to me that with some (rather artificial) sounds it should be possible.
There's a free sound editor called Audacity which is quite nice. With it, I created an asymmetric waveform by first generating a pure tone (sin wave) and then chopping off the positive half. I then copied that, reversed the polarity, and pasted it onto the end of the first sample. So in the end I had a track consisting of two equal parts - first a sin wave with the positive half chopped off, and second a sin wave with the negative half removed. I did this both with and without removing the average DC offset from each half, which didn't make any audible difference as far as I could tell. I tried this first with a 440 Hz sin wave, and couldn't hear a difference between the two halves. However when I tried it starting with a 50 Hz sin wave, there is a clear difference. The sound is a kind of strange (and annoying!) buzz, pretty far from a pure tone, but the two halves are at a different pitch! In particular played over my computer speakers or through headphones connected to my sound card, the second half is lower and has a louder bass component. Played through the SB into phones the effect is more subtle, but still there. >From SB -> amp -> speakers, oddly, there is still a difference but it seems reversed - the first half is at a lower pitch. A spectrum analysis plot reveals no differences - and unless there is a bug in Audacity, there _can't_ be an difference in the spectra, given how I generated the track. So I guess this must be due to non-linearities somewhere. I don't have time to do a proper blind test, but the difference is clear - the two tones have a different overall pitch, which is quite easy to hear. I tried closing my eyes and randomly clicking in different places on the waveform, and I was right every time - it's quite audible. Finally, let me note that this waveform is kind of maximally asymmetric, and such a sound could never be generated by a physical object (and if it could it would be an instrument quite the opposite of "musical"!). So I don't think this result has any consequences for music reproduction. Nonetheless, it's kind of intriguing. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=23759 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
