[PD] Measuring position between two microphones?

[Andy Farnell]

I think the use of [threshold~] is limiting you to block resolution.
Audio to do correlation will give you a theoretical resolution much better
than one block, at half the sampling rate, 0.015m (one and a half
centimeters) for 44kHz.(?) Assuming that the mics are identical, in phase etc.

[snapshot~] seems a better choice than [threshold~] because it gives 
you the instantaneous vaue of a sample. But I'm not quite sure how best
to use it in this context.

It depends on the source, if its an impulse or if it's a periodic wave, for which
correlation approach. I was reading this interesting one recently and
wondered if anyone tried it

 
> - Clip the two signals - i.e. amplify and saturate so the signals become a
> series of 1s and 0s.
> - XOR the result. You will use this result "X" in two ways:
> 1) Integrate X to get Y
> 2) Measure the variance of Y
> When the variance of Y approaches zero, there is similarity.
> Y itself is a measure of time shift between the signals.
> This works for things like sinusoids.
> Fred

If it's for delocalisation/positioning of emitters where you
get to decide what the sound is (and choose a nice ultrasonic
sine wave)  then it seems potentialy fast because it can be 
crudely sampled and carried out as logic.






On Sat, 23 Jun 2007 22:12:53 +0200
Chris <chris at proquariat.de> wrote:

> Hi,
> I made a patch to locate the position of a sound source between two 
> microphones, which looks like this:
> [adc~]
> |         |
> |        [threshold~ 0.2 100]
> |                                        |
> [threshold~ 0.2 100]      |
>                     |     [delay 10]
>                     |      |
>                   [timer]
> 
> So a number of 10ms means that the source is exactly between the two 
> microphones. This patch works kind of reliable and accurate. But I was 
> wondering if there is a better possibility with higher resolution? At 
> the moment I can distinguish the position with an accuracy of 1.333 ms, 
> means I get about 12 different values out of my tube.
> 
> Has anyone an idea how I can get more precise readings? I thought about 
> comparing the amplitudes of the two waves I get, but I have no idea how 
> to do this or if this would be more exact.
> 
> Thanks for any help,
> Chris
> 
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