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Discussion Groups | Matlab DSP | How to filter out a specific frequency band

Technical discussion about Matlab and issues related to Digital Signal Processing.


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How to filter out a specific frequency band - - Jan 1 10:12:59 2009

At the moment I am working on my thesis on "fault detection in pumps
using vibratory signal analysis". This is to be done by comparing two
groups of the signals, one for normal state of the machine and another
attributed to its faulty conditions (in which a specific fault is artificially
imposed to the system under the same working conditions as of the normal
My problem is a high-amplitude noise with unknown source in the both signals
(normal and faulty). From the FFT spectrum I was recording during the data
collecting process the frequency band of this noise could be seen around 2.5 –
3.2 kHz (depending on the working conditions). Here is my question:
How can get rid of this noise by attenuating it from the main signal? Somewhere
I read DWT can act as a bandstop filter. If so, how can I implement it on my
signals using Matlab. Is it principally a effective filter type for such an
application or I should use another type? There are some hints in Matlab's help
but I appreciate if someone could give me an example M file for such a bandstop
Here is some info about my signals:
-	Sampling frequency: 64 kHz
-	Frequency content: up to 25 kHz
-	To be filtered band: 2.5-3.2 kHz
-	Time duration: 10 second
-	The phenomena to be studied are mostly unsteady in nature so after filtering I
am to employ time-frequency techniques like wavelet or STFT to extract features.

Thanks to my major (mechanical eng.) I am not so familiar with DSP theoretical
concepts so I highly appreciate your practical and straight forward

Thank you for your time


Re: How to filter out a specific frequency band - ubaid_abdullah - Jan 2 9:17:53 2009