[time-nuts] Re: Clock specs for audio

[Attila Kinali]

Hoi Bernd,

On Mon, 10 Jan 2022 16:12:44 +0100
"Bernd Neubig" <BNeubig at t-online.de> wrote:

>  There
> argument is often, that the spatial transparency of the sound, i.e. how
> exactly you can locate the sound source (instrument in an orchestra) would
> be noticeably improved by such ultra-low noise OCXO sources. So it should be
> more about time or phase (jitter?) than about frequency....

This argument is still bogus.

Sound localization works on the difference in arrival time at the ears.
We are talking here about dozens to hundres of µs of time differences.
The average human can discern time differences in the order of 10µs
(in terms of a localization setting, other settings have a different threshold).
Let's assume we have someone who is especially trained at this and
can discern time differences down at 1µs. Now let's further assume
for jitter to have little influence it needs to be at least a factor
of 1000 lower... Then we'd be at a jitter spec of 1ns at a bandwidth
of, let's be generous, 1Hz to 20kHz. Even a lowly XO will fulfill
this requirement. And it would be still broadband white noise that
would dominate this jitter, not the close in noise.

Besides, we know from experiments [1,2] that the noise levels can
be pretty substantial (like close to 0dB SNR) before localization
performance degrades noticably.

But yes, the customer is king and if he pays, why not deliver what he wants.

			Attila Kinali


[1] "Sound localization in noise: The effect of signal-to-noise ratio",
by Good and Gilkey, 1996
https://doi.org/10.1121/1.415233

[2] "Sound localization in noise in normal-hearing listeners", 
Lorenzi, Gatehouse and Lever, 1999
https://doi.org/10.1121/1.426719

-- 
In science if you know what you are doing you should not be doing it.
In engineering if you do not know what you are doing you should not be doing it.
        -- Richard W. Hamming, The Art of Doing Science and Engineering