Interesting Papers re temporal resolution Options

[ncdrawl]

http://www.physics.sc.edu/kunchur/Acoustics-papers.htm

http://www.physics.sc.edu/kunchur/papers/FAQs.pdf

[Canar]

If I may grossly oversimplify your argument Axon, you're partially arguing that he's choosing an extreme edge case to test. However, if his intent is to map the boundaries of audibility, wouldn't an edge case be acceptable? I find the conclusion that ultrasonics are perceptible fascinating, and if he's found a case in which they actually are audible, should we not hear it out? Even though it does not represent most cases, if they are truly audible in this case, isn't that worth considering?

As an archivist, I want transparency in all cases, so I don't have to worry about the edge cases. That's why I use FLAC and not MP3. If there is any case where 44.1kHz is not sufficient, isn't that worth devising solutions for?

[Axon]

If I may grossly oversimplify your argument Axon, you're partially arguing that he's choosing an extreme edge case to test. However, if his intent is to map the boundaries of audibility, wouldn't an edge case be acceptable? I find the conclusion that ultrasonics are perceptible fascinating, and if he's found a case in which they actually are audible, should we not hear it out? Even though it does not represent most cases, if they are truly audible in this case, isn't that worth considering?

As an archivist, I want transparency in all cases, so I don't have to worry about the edge cases. That's why I use FLAC and not MP3. If there is any case where 44.1kHz is not sufficient, isn't that worth devising solutions for?

The use of a 7khz square wave as an input here, in this context, seems particularly unrepresentative to me, as a -10db ultrasonic third harmonic, with a signal completely absent of energy at 14khz from other sources, is a profoundly special case. It's not merely that it's an edge case - it is way, way over the edge to begin with. It's like arguing that 16 bits is insufficient because you can hear the noise with the gain raised ~20db above normal (as even shown by Meyer/Moran). Of course you can - but that situation never actually happens in the real world, where music is normalized near 0dbFS and released for an audience that actually wishes to listen to it. More generally, Kunchur never really justifies that input signal very well, and without careful delineation, nothing's stopping anybody from boosting 21khz levels arbitrarily high to get arbitrarily low measured thresholds (like with, for instance, a bipolar pulse train).

In the final reduction ad absurdum, it's hard to tell apart his conclusions apart from a claim that (say) 200khz bandwidth is necessary for audio, because if you play extremely powerful 200khz and 202khz tones, the inevitable intermodulation is audible. The existence of any form of intermodulation, combined with the existence of an ultrasonic bandwidth, necessarily implies that some classes of signals will show audible differences when filtered before distortion. Morevoer, this audibility will exist at any amount of filtering greater than zero, because I'll always be able to hand you a signal that will break threshold at the intermodulation frequency.

A test with ultrasonic content at ranges more representative of real situations would restore validity, but I think that is not going to save his conclusions. In that case, if audibility is shown in the first place, it will almost certainly be above 22us. And at that point it no longer has anything to do with time resolution. But it would be a convincing proof of CD's insufficiency - but before that point is reached, the question is, how would that be possible when every prior attempt has failed?

This post has been edited by Axon: Jul 28 2009, 20:18