From tsato@u-tokyo.ac.jp Tue Oct 24 09:55:57 1995
Path: ashpoly!cascade!bigsur!u-tokyo!tsato
From: tsato@u-tokyo.ac.jp (Tobias Sato)
Newsgroups: comp.dsp
Subject: Discussion: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct24.095557.1771@u-tokyo.ac.jp>
Date: Tue, 24 Oct 1995 09:55:57 GMT
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Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.

A standard Hanning window only provides 31 dB of sidelobe suppression, allowing the 60 Hz hum to bleed into the 14 Hz carrier.
A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor.

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

-- 
Tobias Sato
Opinions expressed are solely my own and not those of University of Tokyo Department of Information Science.
------------------------------------------------------------

From bweber@cern.ch Tue Oct 24 23:12:57 1995
Path: ashpoly!cascade!transat!sunet!nordrelay!cern!bweber
From: bweber@cern.ch (Bastien Weber)
Newsgroups: comp.dsp
Subject: Re: Discussion: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct24.231257.1924@cern.ch>
Date: Tue, 24 Oct 1995 23:12:57 GMT
References: <1995Oct24.095557.1771@u-tokyo.ac.jp>
Organization: European Laboratory for Particle Physics, Geneva
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In article <1995Oct24.095557.1771@u-tokyo.ac.jp>, tsato@u-tokyo.ac.jp (Tobias Sato) 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.

-- 
=== Bastien Weber ===
Dept of Electrical Engineering, European Laboratory for Particle Physics, Geneva
"The hatch is open. Is anyone listening?"

From eperez@unam.mx Fri Oct 27 00:06:57 1995
Path: ashpoly!bigsur!pacrim!jpgate!kamome!unam!eperez
From: eperez@unam.mx (Emi Pérez)
Newsgroups: comp.dsp
Subject: Re: Discussion: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct27.000657.1754@unam.mx>
Date: Fri, 27 Oct 1995 00:06:57 GMT
References: <1995Oct24.095557.1771@u-tokyo.ac.jp>
Organization: Universidad Nacional Autónoma de México (DGSCA)
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In article <1995Oct24.095557.1771@u-tokyo.ac.jp>, tsato@u-tokyo.ac.jp (Tobias Sato) writes:
> Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.
> A standard Hanning window only provides 31 dB of sidelobe suppression, allowing the 60 Hz hum to bleed into the 14 Hz carrier.

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

-- 
Emi Pérez
Tape trading list upon request. SASE required for international mail.