noise..how to regulate it?

Dear chaps,

I have a problem. I have a signal recorded from a ultrasonic
transducer of a chemical reaction. It is rich of noise, expecially the
white one. I tried to filter with normal filter (butterworth band
pass), but I did not obtained a lot of success.
So, I thought was better delete the White gaussian noise with an
adaptive filter. I used the demo of Simuling of LMS but I have
problems to "create" the noise artificially?
What can I do? Which information I need to identify it?
Is it enought to record the noise from the becker without reaction?

Does it work or I must think about a different filter?

Thanks in advance!
Manuel

On Tue, 3 Feb 2004, Manuel Tramontana wrote:

> Dear chaps,
>
> I have a problem. I have a signal recorded from a ultrasonic
> transducer of a chemical reaction. It is rich of noise, expecially the
> white one. I tried to filter with normal filter (butterworth band
> pass), but I did not obtained a lot of success.
> So, I thought was better delete the White gaussian noise with an
> adaptive filter. I used the demo of Simuling of LMS but I have
> problems to "create" the noise artificially?
> What can I do? Which information I need to identify it?
> Is it enought to record the noise from the becker without reaction?
>
> Does it work or I must think about a different filter?
>
> Thanks in advance!
> Manuel
>

your idea of recording just the noise without the reaction is good, but it
assumes that the system is linear.  otherwise, you can't tell what happens
when the reaction is in the system.

so do some tests to see if it's a linear system, or better yet derive it
from the physics of what you're observing.

the other thing is to see whether the noise is stationary.  if it is, then
you can estimate its autocorrelation/color and you can use that as a basis
for simulating the system.

before thinking about solutions, take a step back and see how complicated
the noise model needs to be.  once this is done, the solution is usually
not far behind.

good luck,
julius

-- 
The most rigorous proofs will be shown by vigorous handwaving.
http://www.mit.edu/~kusuma

opinion of author is not necessarily of the institute