[PD-ot] how low (latency) can you go?

Hans-Christoph Steiner hans at eds.org
Sat Dec 16 20:44:22 CET 2006


On Dec 16, 2006, at 1:14 PM, Bryan Jurish wrote:

>
> On 2006-12-16 19:02:08, Hans-Christoph Steiner <hans at eds.org>  
> appears to have written:
>> And always, when talking about latency, I feel the need to point  
>> out the speed of sound: 340 m/s or .34 m/ms.  So if your speakers  
>> are 2m away from you, that's 6ms of latency.  You could spend days  
>> tweaking your machine to get 3ms less latency, or you could move  
>> 1m closer to your speakers.  Puts things into perspective...
>
> indeed 'tis true.  but 5ms vs. 10ms makes a major subjective/ 
> perceptual difference if we're talking about playing an electro- 
> acoustic instrument in and getting a munged signal out...

Do you have any references on that?  I think it could be perseptable  
to a very experienced musician, but I don't think there is a major  
effect.  From the studies that I have read, jitter has a much larger  
affect than latency in terms of affecting performance.   (I need to  
find some references myself... ;)

Also important to note is that conscious processing of sound in the  
brain is actually quite slow.  Yes, the ear can perceive changes on  
the order of
0.05ms (20,000Hz), but your brain is made consciously aware of these  
changes at a much slower rate. You can hear an example of this using  
a oscillating frequency.  A slow change in the frequency of a tone is  
perceived as vibrato: you can consciously hear the wavering pitch.   
As that change in frequency becomes faster, you can no longer  
consciously hear the wavering pitch. Instead you perceive a steady  
tone.  I attached a patch to illustrate this.

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Performers are actually quite adept at adjusting to latency. Just  
think of an orchestra or choir:  there could be 20ms or more of  
latency from one side of the stage to the other, yet its not hard for  
a moderately trained group to handle it.  Another key factor in  
performance is physical feedback, which has a much faster feedback  
loop that the audio system.  Trained musicians can feel a mistake and  
correct it long before the sounds are consciously perceived.  (I  
first saw that in print on one of Miller's papers http:// 
crca.ucsd.edu/~msp/Publications/icmc93.ps)

One realm were I could see that latency would be important would be  
when measuring response time to a stimulus, like in a psychological  
experiment.  But even still, as long as the latency is steady (i.e.  
low jitter), the latency is not a big deal.

.hc

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