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Entry  Tue Nov 27 01:03:42 2012, Ayaka, Update, WienerFiltering, Sound on PSL gauss_psdcoh_mcf.pngtri40_psdcoh_mcf.pnggauss_filters_mcf.pngGauss_estimatefilters_mcf.png
    Reply  Wed Nov 28 23:55:13 2012, Ayaka, Update, WienerFiltering, Sound on PSL tri40_psdcoh_mcf_varioust.pnggauss_psdcoh_mcf_varioust.png
Message ID: 7751     Entry time: Tue Nov 27 01:03:42 2012     Reply to this: 7760
Author: Ayaka 
Type: Update 
Category: WienerFiltering 
Subject: Sound on PSL 

 Last Thursday, I put the speaker and my laptop in the PSL table, and make triangular wave sound with the basic frequency of 40Hz, and Gaussian distributed sound.
(I create the sounds from my laptop using the software 'NHC Tone Generator' because I could not find the connector from BNC to speaker plug.)
And I measured the acoustic coupling in MCF signal. The all the 6 microphones were set in PSL table around PMC and PSL output optics. 

The performance of the offline noise cancellation with wiener filter is below.
(The target signal is MCF and the witness signals are 6 microphones.)

  • With Gaussian sound (Sorry for wrong labeling 'XARM' and no calibration)
    gauss_psdcoh_mcf.png
  • With 40Hz Triangular sound (Sorry for no calibration again)
    tri40_psdcoh_mcf.png

I can see some effects on MCF due to the sound on PSL table. Though I can subtract some acoustic signal and there are no coherence between MCF signal and mic signals, still some acoustic noise remains.
This is maybe because of some non-linearity effects or maybe because we have other effective places for acoustic coupling measurement. More investigations are needed.

Also, I compared the wiener filter and the transfer function from microphones signal to MCF signal. They should be the same ideally.
gauss_filters_mcf.pngGauss_estimatefilters_mcf.png

(Left: Wiener filter, Right: Transfer function estimated by the spectrum. They are measured when the Gaussian sound is on.)

These are different especially lower frequencies than 50 Hz. The wiener filter is bigger at lower frequencies. I guess this adds extra noise on the MCF signal. (see the 1st figure.)
The wiener filter can be improved by filterings. But if so, I want to know how can we determine the filters. It is interesting if we have some algorithms to determine the filters and taps and so on.
The more investigations are also needed.

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