Jean-Marc,
Thank you. I suspect that the actual capability of the hardware in question is
to do front minus back, as in the dual-ported noise cancelling microphones of
the 1940's, with its obvious issues. We are working on another platform that
will have the necessary processing power.
Thanks
Bruce
On May 23, 2014 10:40:51 PM PDT, Jean-Marc Valin <jmva...@jmvalin.ca> wrote:
>On 23/05/14 09:33 PM, Bruce Perens wrote:
>> We had a chat with Jean-Marc about this long ago, but I can't find
>the
>> message. He claims a 3 dB improvement per additional microphone
>(which
>> is maybe why we see between 4 and 8 in modern systems). He has a
>number
>> of papers on this issue, deriving from his work on robotic audition.
>See
>> http://people.xiph.org/~jm/papers/IROS04_711.pdf and there is a
>papers
>> list at http://scholar.google.com/citations?user=l52ospIAAAAJ&hl=en
>
>Not quite. The theoretical improvement from a delay-and-sum beamformer
>(*) is 3 dB every time you *double* the number of microphones, in other
>words, 10*log10(nb_mics).
>
>Cheers,
>
> Jean-Marc
>
>(*) This is assuming the noise is diffuse and uncorrelated between
>mics.
>Smarter beamformers can do better for directional sources, but you can
>also end up with worse if the mics are too close.
>
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