Re: [Audacity-devel] was: 'Re: Classic Filters status', now a little OT
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From: Federico M. <fm...@fc...> - 2015-01-06 05:17:08
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Martin, > I believe nobody can, but it seems contested. If the phase changes > over a second or less, certainly the difference can be heard. This is the sort of case discussed by Roederer. > I can't hear it, can you? Yes, I can hear some modulation. > How did you get the 880.44 Hz? I'm interested to hear your analysis. Sorry to disappoint you, it's very basic. I just looked at the waveform o rather the envelope and observed that it took about 2.5 s to complete sort of a cycle, then I generated a mistuned harmonic multiplyng by 2.001 (which made a beat about that long with 2.000*f). The envelope is similar, not identical, but enough to test the idea. The same as in the case of frequency modulation, the spectrum of a very slight FM is very similar as the spectrum of an amplitude modulation (one tone and two side bands, with the only phase differences) > Hmm. Can they really? I can't tell... Haven't run a double blind test. But more than once I have been surprised by people systematically hearing things I did not. > I'm a bit sceptical, since as I've got older and better at listening, > my hearing has got worse. And are these 'experienced audiophiles' > lucky or not? is something I've often wondered. 'generally accepted' > references would be nice. I don't have any at hand right now, but now and then I come across some comment of the like. I'll pay attention next time and send it to you. >> But the subtle difference probably cannot be perceived at all in the >> presence of fan noise from the computer if not acoustically isolated. > Can you hear it? I don't have an adequate environment. I don't believe even that I am the best subject to test these subtleties, since I have some tinnitus >> A 1 kHz order 10 lowpass Chebyshev has at 1 kHz a phase delay of >> 720º, about 2 ms, while at 100 Hz it has a delay of 0.13 ms. That >> means that there is a difference of about 1.9 ms, which corresponds >> to a distance of about 2 ft, that's why the source may, in theory, >> seem blurred. > OK, it's a theory. Do you (or anybody else) have a procedure that I > can follow to demonstrate the difference in that delay and so (maybe) > be able to hear the problem? Something that we can do in Audacity by > generating waveforms, applying filters and so on? I'd love to try that > out on my young-eared students. OK, I'll try to think of some test. Regards, Federico |