Sampling rates higher than 44.1Khz? Options

[Grand Dizzy]

I recently met a musician who claims he can quite easily hear the difference between 44.1KHz and 96KHz.

This shocked me a little because I'd always been told that the human ear cannot hear any higher quality than CD (44.1KHz) quality.

So... was this guy just lying (or fooled by his senses), or was I being lied to when I was told the human ear cannot hear any higher quality than CD?

This post has been edited by Grand Dizzy: Feb 5 2006, 01:11

[krabapple]

more on the 'beating' issue, from James Johnston:

A Graphical Explanation involving Sampling
http://www.audioasylum.com/audio/general/messages/43134.html

Opener:
"The questions about modulation of sine waves near the Nyquist limit seem to be common and repeated. The image URL here has a plot that, I think, explains how the "beating" comes about due to adding in frequencies that are solely above the Nyquist limit, and thus how filtering them out removes any "beating" one observes in raw, unfiltered data from a DAC (before the anti-imaging filter)."

[hdante]

There's too much interpreting here. I've found a "third-party" argument which mirrors my original statement and I hope it is pretty understandable. However, I insist that the 2 KHz was wrong and 1 KHz would be the correct result (there's the same error in the quote that follows).

(...)
3. The third theory of recording at 96kS/s has to do with high frequency information during the mixing process.

Whenever two audio signals are combined, the result is a harmonic structure that produces additional frequencies as a combination of the summing of the two. If a note is played at 100Hz and another is played at 150Hz, there will be two additional frequencies produced as a result. One at 50 Hz (B-A) and the other at 250Hz (B+A). It is the first - the subtractive - that we shall discuss here. If two frequencies are produced at 30k and 45k, the effect will produce a harmonic overtone at 15k - well within the human hearing spectrum (at least for those of us in our 20's).

While this 15k signal would be picked up on a microphone in the room during a live classical performance, the issue has to do with multitrack performances where the music was tracked on separate microphones in isolated facilities. There would be no opportunity for this high frequency information to be mixed and reproduce these lower harmonic overtones because at 44.1k, the highest frequency recordable is at about 22k.

Theoretically, if we put two oscillators in a room - one at 30k and one at 45k, a microphone would pick up a 15k harmonic that we could hear. If we had the same oscillators in different rooms and recorded them both at 44.1k and mixed them we would not hear this phenomena. If, however, we recorded them at 96k (assuming the filters on the converters rolled off at 48k and not earlier) and mixed them we would once again hear this 15k overtone. This is supposedly an example of where recording and mixing at 96k can achieve different sonic characteristics even if the recording was to be reproduced on a 48k medium. The overtones discussed above would be produced in the mixing process and would endure the downsampling process.

Upon trying to put together this test I had a difficult time finding scientific enough equipment to produce and measure these frequencies. The theory is plausable, but the effect would be fairly minimal as these overtones are at very low amplitude. Regardless, the theory has a chance of holding water if a valid test can be done. I have heard of no such tests. Perhaps we could Roger to oblige us.
(...)

The text is at http://www.musicplayer.com/ubb/Forum2/HTML/001473.html
There's a link there with info about some instruments harmonics. (There's life above 20 kilohertz). By visual inspection, the article doesn't talk about the cited argument. However, it seems to have info on the amount of energy many instruments have above 20 KHz, which may be interesting for those who were considering that the effect (which could be a feature, not a bug) is unlistenable.

[ChiGung]

(...)
Whenever two audio signals are combined, the result is a harmonic structure that produces additional frequencies as a combination of the summing of the two. If a note is played at 100Hz and another is played at 150Hz, there will be two additional frequencies produced as a result. One at 50 Hz (B-A) and the other at 250Hz (B+A). It is the first - the subtractive - that we shall discuss here. If two frequencies are produced at 30k and 45k, the effect will produce a harmonic overtone at 15k - well within the human hearing spectrum (at least for those of us in our 20's).

That is quite nonsense Im afraid hdante. The poster is roughly calculating beat frequencies between tones and confusing them with new tones that have the frequency of the beat. Mind a beat in a tone (or between tones) is definitely not a new tone and doesnt 'look' like a tone in a PCM record or sound like tone in RL. SebG put it like this:

you can also interpret your formula as a 31 kHz sinusoid with an amplitude modulation at a rate of 1 kHz

(the amplitude modulation can be seen in the pcm record as a 2kHz pulsing of the tone.)

Now sebG is one of those who doesnt like people talking about this stuff or attempting to enquire outside of contemporary academic language and references, hence this statement:

Fascinating? Hmm.... May seem so. But I think that some posts here are actually a bit misleading/misinformed.

Unfortunately hes not been inspired to actualy point out any particular misleads or misinforms -which are par for the course in open forum whatever the Tos. And I fear if him or his like do choose to elaborate it will be in a frustrated manner, so watch out for that

good luck'

This post has been edited by ChiGung: Feb 9 2006, 19:01

[hdante]

That is quite nonsense Im afraid hdante. The poster is roughly calculating beat frequencies between tones and confusing them with new tones that have the frequency of the beat. Mind a beat in

Ok, I think we reached the point. What the two links I posted here (about which I've realised my unfortunate belief that they were authoritative) are probably sugesting is that the beat is what is outside the hearing limits, while the tone is what is inside the hearing limits.

The beat, in the guitar tuning sense, is what is off the low hearing limit (eg 5Hz). The beat, in the ultra sonic sense is what is above the high hearing limit, (eg 31 KHz).

About the thing with Sebastian, I've just confirmed. At 440 Hz + 450 Hz I do listen both the 445 Hz tone and the beating.

Now you, ear engineers, say something about those.

Henrique Dante de Almeida

[bug80]

Ok, I think we reached the point. What the two links I posted here (about which I've realised my unfortunate belief that they were authoritative) are probably sugesting is that the beat is what is outside the hearing limits, while the tone is what is inside the hearing limits.

Sorry, I do not think those articles are very authoritative.

About the thing with Sebastian, I've just confirmed. At 440 Hz + 450 Hz I do listen both the 445 Hz tone and the beating.

And how exactly did you do that? If you add two tones of 440 Hz and 450 Hz you should not end up with a 445 Hz tone, since addition is linear. You should hear a superposition of both tones (you should hear them both at once), plus a beating effect, which is again just a temporal change in amplitude, not in frequency.

This post has been edited by bug80: Feb 9 2006, 19:52