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Re: [microsound] talk about supersonic signals and distortion



That is most certainly wrong.

1. You cannot hear much above 20khz so there is absolutely no reason to
encode anything. 44.1 will let you hear as much of any square wave as a
straight wire or higher sampling frequency. At least if all the research is
to be beleived.

2. No, no, no. Nyquist still holds as far as I know. You are again trying to
reproduce information that would be well above the audible range.

3. Exactly, we cant "hear" above 20khz (give or take a few khz) and that is
exactly why (1) and (2) doesnt matter. Try the mathematics and you'll see.

4. As far as I know only the japanese research referred to by Rupert Neve
has made claims above 20khz. And the researchers said no-one could "hear"
above 20khz or even sense it in practical tests. But they measured brain
activity and they cold see a diff on the measurements.

5. No, not at all. there used to be in the 70s and 80s when filtering was in
the analog domain. All A/D chips in use today (and since at least 10 years)
are all oversampling with digital filtering and they behave exactly the same
(work at the same sampling frequencies, use the same filters) no matter your
destination is 44khz or 192khz.

Your claims would mean that Nyquist was wrong. That would certainly
revolutionize the DSP world!!

Den 03-05-18 19.20, skrev "ian stewart" <artsonics@xxxxxxxxxxx>:

> 
> There are several reasons for using frequencies over 20 kHz, and for using
> sample rates over 44.1:
> 
> * at -audible- frequencies, e.g. 12 kHz, you can only differentiate a square
> wave from a sine by encoding overtones above 20 kHz. There is almost no
> resolution in high frequencies at CD sampling rate;
> * for an 11 kHz tone, there are only four data points available per cycle,
> and thus only 3 possible phase displacements. this means encoding the
> 'space' of high frequencies is virtually impossible;
> * even if we may not 'hear' frequencies over 20 kHz, parts of the bone
> structure respond to them;
> * further, many studies indicate that listeners are able to distinguish
> between recordings containing 'ultra-high' frequencies (over 20 kHz) and
> recordings which do not ;
> * 20 kHz is only a median value for the upper limit of human hearing- I've
> seen speculation that some listeners may be able to hear up to 25 kHz;
> * there are countless other problems with encoding high frequencies at 44.1-
> corrective circuits that smooth out high frequency waves because the low
> resolution causes distortion, and anti-aliasing filters that preclude
> reliable frequency data even in the high end of the -audible- range.
> 
> some of the above information is from Dominique Bassal's paper on mastering
> and electroacoustic music, which will soon be available from the CEC
> webpage.
> 
> best,
> Ian
> 
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