4 ms·

For an article containing a lot of "well, if you knew signal processing..." there are two fairly major oversights: 1) Any well-designed system is going to have

For an article containing a lot of "well, if you knew signal processing..." there are two fairly major oversights: 1) Any well-designed system is going to have headroom. Period. Just because 48kHz can capture the frequencies the human hear theoretically, it's always good to have a little wiggle room. This comes into play even more with interactive situations: humans are particularly sensitive to jitter. Having an "overkill" sample rate lets you seamlessly sync things easier without anyone noticing. 2) 192kHz comes with an additional benefit besides higher frequencies: it also means more granular timing for the start and stop of transients. More accurate reverb would be the obvious example. I don't know if the human ear can discern the difference between 0.03ms and 0.005ms but it's something I don't see mentioned often.

Joeboy 15y ago
> I don't know if the human ear can discern the difference between 0.03ms and 0.005ms but it's something I don't see mentioned often That's the time it takes sound to travel 8mm. Do you think you could tell if an instrument was positioned differently by 8mm?
- barrkel 15y ago
  The ears distinguish directional audio in part from timing differences in what hits each ear. http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization cites http://web.archive.org/web/20100410235208/http://www.cs.ucc.ie/~ianp/CS2511/HAP.html http://web.archive.org/web/20100410235208/http://www.cs.ucc.... that suggests the brain is sensitive to timing differences between ears as low as 10 microseconds, or 0.01ms.
  - xiphmont 15y ago
    It's not the timing differences, it's the phase differences. The ear is exceptionally sensitive to phase differences between the ears below 1kHz. This information is captured exactly (to well beyond the naive precision of the sampling clock) for any frequency below Nyquist.
- wickedchicken 15y ago
  I get 10mm vs 1.7mm but it's roughly the same argument http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.03ms+in+mm http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.03ms... http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.005ms+in+mm http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.005m...
ars 15y ago
0.03ms is 33kHz - you can't, no matter how much you want to, make a granular timing that is faster than at least one cycle of the frequency you are using. 0.005ms is 200kHz BTW.
- nullc 15y ago
  This isn't true. Sample a bandlimited impulse. The exact timing is encoded into the gibbs oscillations of the signal. So long as you have a high enough SNR you can have timing as precise as you want. (and because the ear doesn't work with ultrasonics— it is itself bandlimited— it uses the same phenomena for timing)
jaylevitt 15y ago
I'm pretty sure that #2 isn't true; signal processing folks will be able to phrase this better than I can, but I think that if you have enough information to capture the waveform at a given frequency, you also have enough information to precisely place it in time - phasing errors are more likely due to quantization error, which is about bit depth, not sample rate. No?
- aiscott 15y ago
  [edited: I was wrong]
  - jaylevitt 15y ago
    But at a given sample rate, if I'm sampling at bit depth 2, doesn't that quantization error end up temporally shifting the sine wave I'm reconstructing?
    - deleted 15y ago
      [deleted]
  - rmcclellan 15y ago
    This is completely incorrect, by shannon (http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samplin...). The sampling frequency determines the maximum frequency that can be captured, not the temporal resolution. That said, a transient containing higher frequencies will be sharper than a transient that doesn't, but its onset time resolution will not be determined at all by the sample rate. Said another way, two band limited pulse signals with different onset times, no matter how arbitrarily close, will result in different sampled signals.
    - aiscott 15y ago
      You are right.
    - wickedchicken 15y ago
Anechoic 15y ago
humans are particularly sensitive to jitter. Humans are sensitive to jitter, but jitter isn't a major problem with modern digital electronics and reclocking strategies. This ArsT thread hashed out these issues a couple of months ago: http://arstechnica.com/civis/viewtopic.php?f=6&t=1164451&p=22465435&hilit=jitter#p22465435 http://arstechnica.com/civis/viewtopic.php?f=6&t=1164451...
sjwright 15y ago
> Having an "overkill" sample rate lets you seamlessly > sync things easier without anyone noticing. You can get the same theoretical benefit by oversampling on playback. And a lot of audio equipment does just that. > 192kHz ... also means more granular timing for the > start and stop of transients. Not really, for two reasons -- unless you're talking about glitch music, transients are unlikely to ever be so sudden that the difference between 0.03ms and 0.005ms could possibly matter.
xiphmont 15y ago
1) 48kHz sampling does include headroom. 2) increased sampling rate does not improve timing. This also has been researched in detail (because it sounds like it could possibly be true given that the ears can phase match to much greater granularity than the sample clock). It was found false in practice, and in retrospect, the sampling theorem explains why. The Griesinger link discusses this with illustrations, and provides a bibliography.
- nullc 15y ago
  To avoid the trouble of digging up the link: http://www.davidgriesinger.com/intermod.ppt http://www.davidgriesinger.com/intermod.ppt Slides 29-35 address this point.
rdtsc 15y ago
> it's always good to have a little wiggle room 48kHz already has enough 'wiggle room'. How many people do you personally know that can hear a 24kHz sine tone? > more granular timing for the start and stop of transients. ... it's something I don't see mentioned often. Probably because it doesn't make sense. Human ears cannot hear frequencies about 24kHz and Nyquist tells us that 48kHz is enough to completely capture all the detail of a signal at that frequency and below.

Joeboy 15y ago

> I don't know if the human ear can discern the difference between 0.03ms and 0.005ms but it's something I don't see mentioned often That's the time it takes sound to travel 8mm. Do you think you could tell if an instrument was positioned differently by 8mm?

barrkel 15y ago
The ears distinguish directional audio in part from timing differences in what hits each ear. http://en.wikipedia.org/wiki/Sound_localization http://en.wikipedia.org/wiki/Sound_localization cites http://web.archive.org/web/20100410235208/http://www.cs.ucc.ie/~ianp/CS2511/HAP.html http://web.archive.org/web/20100410235208/http://www.cs.ucc.... that suggests the brain is sensitive to timing differences between ears as low as 10 microseconds, or 0.01ms.
- xiphmont 15y ago
  It's not the timing differences, it's the phase differences. The ear is exceptionally sensitive to phase differences between the ears below 1kHz. This information is captured exactly (to well beyond the naive precision of the sampling clock) for any frequency below Nyquist.
wickedchicken 15y ago
I get 10mm vs 1.7mm but it's roughly the same argument http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.03ms+in+mm http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.03ms... http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.005ms+in+mm http://www.wolframalpha.com/input/?i=speed+of+sound+*+0.005m...

ars 15y ago

0.03ms is 33kHz - you can't, no matter how much you want to, make a granular timing that is faster than at least one cycle of the frequency you are using. 0.005ms is 200kHz BTW.

nullc 15y ago
This isn't true. Sample a bandlimited impulse. The exact timing is encoded into the gibbs oscillations of the signal. So long as you have a high enough SNR you can have timing as precise as you want. (and because the ear doesn't work with ultrasonics— it is itself bandlimited— it uses the same phenomena for timing)

jaylevitt 15y ago

I'm pretty sure that #2 isn't true; signal processing folks will be able to phrase this better than I can, but I think that if you have enough information to capture the waveform at a given frequency, you also have enough information to precisely place it in time - phasing errors are more likely due to quantization error, which is about bit depth, not sample rate. No?

aiscott 15y ago
[edited: I was wrong]
- jaylevitt 15y ago
  But at a given sample rate, if I'm sampling at bit depth 2, doesn't that quantization error end up temporally shifting the sine wave I'm reconstructing?
  - deleted 15y ago
    [deleted]
- rmcclellan 15y ago
  This is completely incorrect, by shannon (http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samplin...). The sampling frequency determines the maximum frequency that can be captured, not the temporal resolution. That said, a transient containing higher frequencies will be sharper than a transient that doesn't, but its onset time resolution will not be determined at all by the sample rate. Said another way, two band limited pulse signals with different onset times, no matter how arbitrarily close, will result in different sampled signals.
  - aiscott 15y ago
    You are right.
  - wickedchicken 15y ago

Anechoic 15y ago

humans are particularly sensitive to jitter. Humans are sensitive to jitter, but jitter isn't a major problem with modern digital electronics and reclocking strategies. This ArsT thread hashed out these issues a couple of months ago: http://arstechnica.com/civis/viewtopic.php?f=6&t=1164451&p=22465435&hilit=jitter#p22465435 http://arstechnica.com/civis/viewtopic.php?f=6&t=1164451...

sjwright 15y ago

> Having an "overkill" sample rate lets you seamlessly > sync things easier without anyone noticing. You can get the same theoretical benefit by oversampling on playback. And a lot of audio equipment does just that. > 192kHz ... also means more granular timing for the > start and stop of transients. Not really, for two reasons -- unless you're talking about glitch music, transients are unlikely to ever be so sudden that the difference between 0.03ms and 0.005ms could possibly matter.

xiphmont 15y ago

1) 48kHz sampling does include headroom. 2) increased sampling rate does not improve timing. This also has been researched in detail (because it sounds like it could possibly be true given that the ears can phase match to much greater granularity than the sample clock). It was found false in practice, and in retrospect, the sampling theorem explains why. The Griesinger link discusses this with illustrations, and provides a bibliography.

nullc 15y ago
To avoid the trouble of digging up the link: http://www.davidgriesinger.com/intermod.ppt http://www.davidgriesinger.com/intermod.ppt Slides 29-35 address this point.

rdtsc 15y ago

> it's always good to have a little wiggle room 48kHz already has enough 'wiggle room'. How many people do you personally know that can hear a 24kHz sine tone? > more granular timing for the start and stop of transients. ... it's something I don't see mentioned often. Probably because it doesn't make sense. Human ears cannot hear frequencies about 24kHz and Nyquist tells us that 48kHz is enough to completely capture all the detail of a signal at that frequency and below.