Acoustic Position Measuring Device

Russell Sears sears at
Tue Aug 19 21:19:22 CEST 2008

Charles Pax wrote:
> The problem with having an external speaker or microphone is that such a
> solution does not simplify the situation. Sure, it would make the Freerunner
> (plus some stuff) into a measuring device, but if we need a second piece of
> hardware to take measurement, we may as well just carry around a tape
> measure. Oh well.

Right, but I need to have a hands free headset so I can listen to music, 
so it's not a second piece of hardware.  Admittedly, I could put a piece 
of tape on the cord every inch and get the same effect...

I wonder if there's some other application of sending out a chirp and 
recording it.  Maybe the FR could use echo to characterize acoustic 
environments.  Then it would know if you've left it in a drawer, pocket, 
car, concert hall, etc...

There's also echo cancellation, which the FR desperately needs, and is a 
similar trick.

> So the theory seems plausible. When I get my Freerunner (when are they back
> in stock?!) I'll have to do some testing. Thanks for the input, folks.

You could probably develop it on a linux laptop and alsa.  For this app, 
the main difference between the platforms is that the FR doesn't have a 
floating point unit, and it uses a different microphone jack.


> -Charles
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