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Entry  Mon Nov 5 20:37:01 2012, Ayaka, Update, WienerFiltering, Play with wiener filtering estimate.pngWfilter_notch.png
    Reply  Thu Nov 8 10:11:58 2012, Ayaka, Update, WienerFiltering, Play with wiener filtering document.pdfestimate.pngR_model.png
Message ID: 7672     Entry time: Mon Nov 5 20:37:01 2012     Reply to this: 7688
Author: Ayaka 
Type: Update 
Category: WienerFiltering 
Subject: Play with wiener filtering 

 I am trying to find what limits the reduction rate with wiener filtering.
I did some calculations below:

Reduction rate estimation by microphone noise
estimate.png

When the instrumental noise (noise in microphone) and noise injected to signal after the acoustic signal is injected exist, the noise cancellation rate is limited. (I will write a short document about it later.) I assumed that there is only instrumental noise and that the other noise in PMC is below enough, and calculated the cancellation rate. The instrumental noise is modeled according to the measurement before (ELOG).
The green line is the original PMC signal, the red one is PMC residual error, and the blue one is PMC residual error estimated by the cancelling rate.
Around 30 - 80 Hz, the wiener filtering seems to be already good enough. However, I do not know what limits the cancellation rate (such as 100 - 200 Hz).

 

Filtering signals

Wfilter_notch.png

I hypothesized that the wiener filter is not good because of some peaks or other noise. So I filtered the PMC signal and mic signal to see the difference.
The red line is wiener filter with no filters, the blue one is with filters (low pass, high pass, and notch).
The wiener filter seems to get smoother but the PMC residual error did not change at all.

 

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