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hello. i got some kind of problem with acoustic feedback. I need to
create an algorithm in C language, which fights the acoustic feedback.
It means, for instance, when i put the microphone device close to the
speaker the feedback occurs, and it is supressed at once. Could
anybody help me? thanks and greetings

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Why does it have to be in C? Why could it not
be in machine code or assembler? Or, if you
wanted to illustrate that you were a tyro, in Forth?)

I suggest that you read up on Echo Cancellation, a topic
well-covered in the literature. (I suggest, rather than explain, because
it's
not yet an area of expertise for me, and you can do the
reading just as effectively as I can)

"decyL" <d...@poczta.fm> wrote in message
news:9...@posting.google.com...
> hello. i got some kind of problem with acoustic feedback. I need to
> create an algorithm in C language, which fights the acoustic feedback.
> It means, for instance, when i put the microphone device close to the
> speaker the feedback occurs, and it is supressed at once. Could
> anybody help me? thanks and greetings

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"Airy R. Bean" <a...@lycos.co.uk> wrote in message
news:c1na4q$1kttuu$1...@ID-217727.news.uni-berlin.de...
> Why does it have to be in C? Why could it not
> be in machine code or assembler? Or, if you
> wanted to illustrate that you were a tyro, in Forth?)
>
> I suggest that you read up on Echo Cancellation, a topic
> well-covered in the literature. (I suggest, rather than explain, because
> it's
> not yet an area of expertise for me, and you can do the
> reading just as effectively as I can)
>

Why should he read up on echo cancellation? The problem and mechanism is
quite different.

What he needs is a automatic notch filter. This is like a project I used for
one of my students last year.

(Why should he not use C? With modern hardware there is rarely a need to use
machince code or assembler to get the required speed. )

How are you getting on answering my questions about the unit sampling pulse?

Chimera

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The most effective algorithm for killing feedback fast is to reduce gain!
This however has the side effect of reducing the gain. :-)

You can also employ automatic notch filters that reduce the gain only at the
frequencies are feeding back.  But if you have too much loop gain (e.g. the
microphone is too close to the speaker) this won't help because basically
all frequencies are feeding back at once.  You'll get rid of one and another
will pop up.  At that point, cutting overall gain is the only answer.

Do some reading on the existing hardware devices to see how they work.
Sabine is a good place to start looking.

"decyL" <d...@poczta.fm> wrote in message
news:9...@posting.google.com...
> hello. i got some kind of problem with acoustic feedback. I need to
> create an algorithm in C language, which fights the acoustic feedback.
> It means, for instance, when i put the microphone device close to the
> speaker the feedback occurs, and it is supressed at once. Could
> anybody help me? thanks and greetings

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.