View Full Version : Wanted (again!): Digital Filter for A-Symmertical Noise

Roger V. Gonzalez
05-04-1994, 12:20 AM
Dear Biomech Subscribers:

Sorry for once again posting this notice but this is a better description
of our problem.

Does anyone out there know of a digital processing code which does a good
job at filtering out A-symmetrical (one sided) noise in raw data?

We are experiencing difficulty processing analog data contaminated by
bursts of high frequency noise which is not symmetrically distributed
around the true signal. The frequency content of our signal is < 20 Hz,
and our sample rate is 1000 Hz. The noise is about 100-300 Hz. In this
situation, if the noise were symmetrically distributed about the signal a
low-pass filter would do the trick. However we find that low-pass filtering
the bursts of asymmetrical noise produces low frequency "waves" in the
resulting signal.

Recently I have found that implementing a Rank-Order filter with a small
window and taking the low value and then low-pass filtering the Rank-Order
result could help but will fail when the raw signal asymmetrical noise
"switches" to the other side of the true signal.

Thanks to anyone who can help.

--------------------------------------------------------+ THE EYES OF TEXAS
Roger V. Gonzalez, M.S., P.E. (Doctoral Candidate) | ___ ___
Mechanical Engineering, Mail Code C2200 | \_ \ _____ / _/
Engineering Teaching Center, 3.104 | \ \_/ \_/ /
The University of Texas at Austin | \__ O O __/
Austin, TX, USA 78712 | \ < > /
TEL: (512) 471-5718 / 471-5615 FAX: (512) 471-7683 | \___/
Internet E-mail: roger@armus.me.utexas.edu |
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