From mgirard@cmu.edu Tue Nov 12 06:52:50 1996
Path: ashpoly!cascade!bigsur!cmu!mgirard
From: mgirard@cmu.edu (Mikhail Girard)
Newsgroups: comp.dsp
Subject: Data: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996Nov12.065250.1569@cmu.edu>
Date: Tue, 12 Nov 1996 06:52:50 GMT
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Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.

At 14.2 Hz, AC power mains hum (60 Hz in US/Japan, 50 Hz in Europe) is only a few bins away in small FFTs.
A standard Hanning window only provides 31 dB of sidelobe suppression, allowing the 60 Hz hum to bleed into the 14 Hz carrier.

Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble.

-- 
Mikhail Girard | mgirard@cmu.edu
PGP Key fingerprint: FBDC A923 C4AF E599
"Keep the channels open."

From bperez@hanse.de Wed Nov 13 01:28:50 1996
Path: ashpoly!bigsur!pacrim!krgate!eunha!hanse!bperez
From: bperez@hanse.de (Bill Pérez)
Newsgroups: comp.dsp
Subject: Re: Data: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996Nov13.012850.1339@hanse.de>
Date: Wed, 13 Nov 1996 01:28:50 GMT
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In article <1996Nov12.065250.1569@cmu.edu>, mgirard@cmu.edu (Mikhail Girard) writes:
> Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.

I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection.

-- 
Bill Pérez | bperez@hanse.de
PGP Key fingerprint: B6F3 2577 5124 6222
"Keep the channels open."

From bvasiliev@pipeline.com Wed Nov 13 18:43:50 1996
Path: ashpoly!cascade!mxgate!coyoacan!pipeline!bvasiliev
From: bvasiliev@pipeline.com (Bill Vasiliev)
Newsgroups: comp.dsp
Subject: Re: Data: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996Nov13.184350.5607@pipeline.com>
Date: Wed, 13 Nov 1996 18:43:50 GMT
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In article <1996Nov13.012850.1339@hanse.de>, bperez@hanse.de (Bill Pérez) writes:
> I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection.

Don't forget that if you downsample to 64 Hz first, your FFT resolution jumps to 0.015 Hz per bin with a modest 4096-point transform.

-- 
Bill Vasiliev
Opinions expressed are solely my own and not those of The Pipeline Internet Network.
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From npark@inria.fr Thu Nov 14 00:18:50 1996
Path: ashpoly!bigsur!pacrim!krgate!eunha!inria!npark
From: npark@inria.fr (Natalia Park)
Newsgroups: comp.dsp
Subject: Re: Data: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996Nov14.001850.5643@inria.fr>
Date: Thu, 14 Nov 1996 00:18:50 GMT
References: <1996Nov12.065250.1569@cmu.edu> <1996Nov13.012850.1339@hanse.de>
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In article <1996Nov13.012850.1339@hanse.de>, bperez@hanse.de (Bill Pérez) writes:
> I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection.

Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz.

-- 
Natalia Park
Opinions expressed are solely my own and not those of INRIA Rocquencourt.
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