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At 09:36 PM 3/10/98, Michael P. Hughes, Ph.D. wrote: >At 10:49 AM 3/10/98 -0800, you wrote: >>>To add fuel about sounds and feels of sound, I read somewhere a great >>>history for those who think that beyond 20 Khz (at best) there is no >>>reason to possibly ear anything. >> >>I think it's actually Mr. Neve who talks about this. I think the deal is >>that you can't hear a continuous tone over 20KHz (lower if you've abused >>your ears like me....) but you can discern transients that have higher >>frequencies. I think Neve would demonstrate this by switching a 15KHz >sine >>wave and a 15KHz square wave. All the frequencies that make it a square >>wave are above the human range of hearing, so it should sound the same as >>the sine wave, but supposedly it doesn't. > >Do the higuer harmonics on a square wave count as transients? no, you're right, it isn't really. The thinking was that the different edge rate on the squarewave was discernible, and that ears had some different mechanism for sensing level transitions. Probably is was a bucket of doo-doo intended to sell more expensive Neve consoles. I never checked into it, so I don't really know the Truth. >>well, that's another thing with poor quality digital gear. If the audio >>input is not filtered right and you put higher frequencies into it, they >>will alias into the audio. Basically they mirror around the 1/2sample >rate >>frequency. It's sort of a cool affect, but a terrible thing to do to >music. >>If the aliasing frequencies are low in the first place, the result will >be >>subtle and give you that uncomfortable feeling. > >I was just thinking that - the ear supposedly picks up sound by >registering >the beats along the ear cana via the little hairs. Could it be that stuff >at 56kHz is being aliased to a lower frequency in the ear? Or that there >is a standing wave resonance within the ear at that frequency? Or that >the >hair resonate at that frequency? I doubt it. More likely simple filter theory. 56KHz is not much more than an octave above 20KHz. A resonance peak at 56k could easily be having a small affect under 20k. And it could be that there were other problems in that circuit that were more blatant, and the engineer just found something he wanted to find in order to justify his marketing campaign. Audio engineers generally keep a very safe distance from things like physics and math. kim _______________________________________________________ Kim Flint 408-752-9284 Mpact Systems Engineering kflint@chromatic.com Chromatic Research http://www.chromatic.com