Re: Frequency response was Re: [linux-audio-user] Audiophile CD's

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Subject: Re: Frequency response was Re: [linux-audio-user] Audiophile CD's
From: Tony Lambley (tonyl_AT_vextech.net)
Date: Tue Jan 29 2002 - 01:05:53 EET


Double hummm. Does anyone subscribe to the glass of water theory/belief?

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, 28 Jan 2002, [iso-8859-1] Jörn Nettingsmeier wrote:

> Jason wrote: > > > > On Mon, 28 Jan 28 you Ross wrote: > > > > > Well, if a sound outside of my hearing range affects a sound inside my > > > > > hearing range, I don't need to study the sound that was too high - if I > > > > > could hear artifacts of the interaction, I can simply study the > > > > > interaction. > > > > > > > > I was under the impression the resonant harmonics, artifacts etc. can be the > > > > result of unheard as well as heard sonics interacting and that the playback > > > > (percieved sound) of subsequent recording would suffer if that data was not > > > > included with the recording or alter by adding it after the fact. similar to > > > > the phono preamp mentioned earlier for the "vinyl warmth" effect. > > > > > > I'm not an acoustic enginner and I'm not a sampling theory expert. But this > > > idea just doesn't jive with the way waveforms work. If the following analysis > > > is wrong, someone _please_ correct it. > > > > > > Let's say I have some waveform A that I can hear, and some waveform B that is > > > too high. Let's say that you are capable of identifying A (it's a simple 440Hz > > > sine wave). Now, assume that sounding A and B together produces an audibly > > > different sound. Since it is distinguishable from A, and B is inaudible, the > > > tone of A and B must be a different waveform (call it C; it's equal to A+B). > > > Since I can hear C, it must be below 22kHz. By the Nyquist Theorem I can sample > > > this waveform at 44.1kHz and capture it completely. > > > > Close, hearing is actually kind of strange, and there are different parts > > of our ears that pick up different frequencies in different ways. I'd like > > to be able to explain that more clearly but it's a lot of Voodoo that I > > don't have a very good understanding of. > > > > That having been said, the Nyquist theorem not only applies to > > fundamentals, like A, but also to overtones like B. So if A is a > > fundamental, and B is an overtone creating the composite waveform C, and > > both a and b are are sub 22.05khz, then theoretically sampling at 44.1 > > will accurately > > capture the frequency of both a and b, and therefore the correct frequency > > and C. Timbre however, is a function of waveshape not frequency; the > > closer a signal > > gets to the Nyquist cutoff, the more generic it's shape becomes. > > true, but you needn't care. any "wave shape" other than plain sine > means "additional overtones above the fundamental", because each and > every shape can be expressed in terms of a sum of sine waves with > different frequencies. > > a sawtooth wave for example is nothing else than a mix of f + 2f + > 3f + 4f + 5f ... (where the amplitudes decrease as the factor gets > higher. when you draw the graph, it will gradually begin to resemble > a sawtooth, and it becomes less wobbly the more higher components > you add. > > thus, their frequency is higher. you'll get all relevant overtones > up to the 20something khz rolloff, but nothing higher, which you > couldn't hear anyway. > > hmmm. I'm really not convinced that hearing works by picking apart complex waveforms into fundamentals. Can anyone recommend any good books on psycho-acoustics that aren't *too* heavy on the calculus? If my thinking is wrong on this, I really want to correct it.

-- YankTheChain.com - You can pretend we're not here. That's what I do.

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