two channel adaptive noise cancelling

Hi, 

I biult a two channel adaptive noise cancelling system. I used one
microphone as a primary microphone, and the second one as noise microphone
and picked up noise signal only. However, I found that this noise
microphone also picks up a certain amount of speech, and introduce
significant speech distortion after ANC. Can anybody give me some
suggestions how to decrease this speech distortion? From both hardware and
signal processing algorithms? Thanks a lot!

"Jing" <jing.deng@gmail.com> wrote in message
news:XZqdnYypOuTj6rvYnZ2dnUVZ_sKdnZ2d@giganews.com...
> Hi,
>
> I biult a two channel adaptive noise cancelling system. I used one
> microphone as a primary microphone, and the second one as noise microphone
> and picked up noise signal only. However, I found that this noise
> microphone also picks up a certain amount of speech, and introduce
> significant speech distortion after ANC. Can anybody give me some
> suggestions how to decrease this speech distortion? From both hardware and
> signal processing algorithms? Thanks a lot!

This is one of the problems with the classical Widrow approach. You need to
keep the microphones together and perhaps even have an array of mics. Then
you are into the realms of Beamforming etc.


M.



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Posted via a free Usenet account from http://www.teranews.com

Hi,

But if I place two microphones together, I mean, very close to each other,

general beamforming won't work well for this case. As distance between two
microphones is very important for noise reduction. Did I get you
correctly?
Thanks.

>
>This is one of the problems with the classical Widrow approach. You need
to
>keep the microphones together and perhaps even have an array of mics.
Then
>you are into the realms of Beamforming etc.
>
>
>M.
>
>
>
>-- 
>Posted via a free Usenet account from http://www.teranews.com
>
>

"Jing" <jing.deng@gmail.com> wrote in message
news:CJidnUH7U7l-ebvYnZ2dnUVZ_sGdnZ2d@giganews.com...
>
> Hi,
>
> But if I place two microphones together, I mean, very close to each other,
>
> general beamforming won't work well for this case. As distance between two
> microphones is very important for noise reduction. Did I get you
> correctly?
> Thanks.
>
> >
> >This is one of the problems with the classical Widrow approach. You need
> to
> >keep the microphones together and perhaps even have an array of mics.
> Then
> >you are into the realms of Beamforming etc.
> >
> >
> >M.
> >
> >
> >
> >--
> >Posted via a free Usenet account from http://www.teranews.com
> >
> >
>
>

When you put them together there is a slight difference in interpretation.
You may need a voice activity detector for instance and update during noise
periods only.(otherwise freeze the weights). Look for papers on hearing aid
adaptive noise cancellation. I don't believe the distance is as crucial as
people make out though too close is not a good idea. Let's say the distance
between the ears of an average human.
There is a large literature on this - what is your application?

M.



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Posted via a free Usenet account from http://www.teranews.com