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Tech Square Technical and speculative discussion of amps, cables and other topics. |
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Tech Square Technical and speculative discussion of amps, cables and other topics. |
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In Reply to: Re: even the (double) blind engineer can explain without appeal to "transient resolution" posted by john curl on August 29, 2003 at 14:21:03:
Just pointing out that the relative Amplitude differences vs frequency below 20 KHz are sufficient to explain your being able to hear the difference between 35 and 100 KHz 1st order filters. The double blind test crowd find that people can detect 0.1 dB level differences, even if they only appear over a few octaves.Psychoacoustic studies have shown that sensitivity to relative phase of harmonics at low to mid audio frequencies does exit for some test tones, but at high frequencies the fundamental physiology of phase detection rolls off substantially as the information from the bending of the “hair†has to travel by diffusion from the base of the “hair†to the other end of the cell where it causes the release of neurotransmitters which diffuse across the synapse to auditory nerves which then fire at a rate that saturates at ~ 1 KHz pulse rate. In cats (which I think I recall are able to hear up to 50KHz) the electric potential from the ion diffusion across the hair cell rolls off above 4 KHz. The brain does extract subtle details from aggregating many channels of nerve pulse rate data and further confounds determination of limits by our capacity for learning in response to stimulus but enjoyable electronically reproduced audio experiences universally rely on psychoacoustic illusions – proof that some audio information is lost or ignored.
Amplitude frequency response discrimination is well established and sufficient to explain your results. I am not advocating adding high frequency phase shift (or more accurately; frequency variable group delay from nonlinear phase shift), just puzzled by the apparent leap to the less established possible explanation. In modern audio electronics design it should be easy to improve on even the 100 KHz 1st order filter’s amplitude and phase response over the audio frequency range with 96 or 192 KHz mastering. Based on my current understanding I would certainly allow small high frequency phase errors in order to reduce amplitude errors.
(I did recalculate and posted the correction less than an hour after my 1st post, I would have edited the 1st post for accuracy if jneutron hadn’t already “tagged†it)
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Follow Ups
- Amplitude variation still seems the simpler explaination - jcox 20:01:34 09/01/03 (1)
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