Reply by Al Clark April 30, 20052005-04-30
Jerry Avins <jya@ieee.org> wrote in news:d8qdnarlmuDJEe_fRVn-hg@rcn.net:

> Gie78 wrote: >> Hi, >> >> some days before I asked you something about the LMS and the NLMS. >> Now I am would take one step forward to the FXLMS. I have achieved >> very good results in signal attenuation with the NLMS (about 200db for >> white and colored noise input signals),but with the fxlms the noise >> reduction ratio decreased to 3dB. > > 200 dB is a voltage ratio of 1 to 10,000,000,000. How do you measure it? > > ... > > Jerry
I usually use my 34 bit ADC. Of course, the Johnson noise of my 1 ohm resistors are a problem. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Reply by Jon Harris April 29, 20052005-04-29
"Jerry Avins" <jya@ieee.org> wrote in message
news:d8qdnarlmuDJEe_fRVn-hg@rcn.net...
> Gie78 wrote: > > Hi, > > > > some days before I asked you something about the LMS and the NLMS. > > Now I am would take one step forward to the FXLMS. I have achieved > > very good results in signal attenuation with the NLMS (about 200db for > > white and colored noise input signals),but with the fxlms the noise > > reduction ratio decreased to 3dB. > > 200 dB is a voltage ratio of 1 to 10,000,000,000. How do you measure it?
Well, if he's using floating point numbers (this is digital after all), it might be possible, though still not likely for an adaptive filter algorithm. But I am guessing this is a typo and maybe he meant 20dB? -- Jon Harris SPAM blocked e-mail address in use. Replace the ANIMAL with 7 to reply.
Reply by Jerry Avins April 29, 20052005-04-29
Gie78 wrote:
> Hi, > > some days before I asked you something about the LMS and the NLMS. > Now I am would take one step forward to the FXLMS. I have achieved > very good results in signal attenuation with the NLMS (about 200db for > white and colored noise input signals),but with the fxlms the noise > reduction ratio decreased to 3dB.
200 dB is a voltage ratio of 1 to 10,000,000,000. How do you measure it? ... Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Sverre Hestetun April 29, 20052005-04-29
On Fri, 28 Apr 2005, Gie78 wrote:

> Hi, > > some days before I asked you something about the LMS and the NLMS. > Now I am would take one step forward to the FXLMS. I have achieved > very good results in signal attenuation with the NLMS (about 200db for > white and colored noise input signals),but with the fxlms the noise > reduction ratio decreased to 3dB. > I use a simple 1 sample delay as secondary path and the same for the > estimated secondary path. When I use a correlated input signal like a > sinus the attenuation is similar to the simple NLMS but for white > noise the performance decrease. > > Now may question, is there anybody who has some experience with the > FXLMS because may coworkers aren`t familiar with the FXLMS. > Is it a normal result or could there a mistake in my Matlab skript?
Hi! For filtered x-lms in the feedforward case, the performance of your system mainly depends on some prior knowledge about your signal before sent to the plant. Therefore I think you should have a delay in your primary path, then I think you will see the results are getting better. The delay should be equal to or larger than the delay in the secondary path to get good results. The results also depend on the crosscorrelation between the disturbance signal and the filtered reference signal. I recommend you to look in Stephen Elliots "Signal Processing for active control" or Kuo and Morgan "Active Noise Control Systems" for more information on F-XLMS.
> How can I improve the performance for uncorrelated signals? I have also > changed the secondary path to an highpass filter I think its more > realistic, but the result for uncorrelated signals didn`t improve. > > So I would be glad if I can found anybody for a discussion about the > FXLMS. > > Thanks Markus >
Reply by Gie78 April 29, 20052005-04-29
Hi,

some days before  I asked you something about the LMS and the NLMS.
Now I am would  take one step forward to the FXLMS. I have  achieved
very good results in signal attenuation with the NLMS (about 200db for
white and colored noise input signals),but with the fxlms the noise
reduction ratio decreased to 3dB.
I use a simple 1 sample delay as secondary path and the same for the
estimated secondary path. When I use a correlated input signal like a
sinus  the attenuation is similar to the simple NLMS but for white
noise the performance decrease.

Now may question, is there anybody who has some experience with the
FXLMS because may coworkers aren`t familiar with the FXLMS.
Is it a normal result or could there a mistake in my Matlab skript?
How can I improve the performance for uncorrelated signals?
I have also changed the secondary path to an highpass filter I think
its more  	realistic, but the result for uncorrelated signals didn`t
improve.

So I would be glad if I can found anybody for a discussion about the
FXLMS.

Thanks Markus