From hkim@purdue.edu Mon Feb 14 22:17:05 1994
Path: ashpoly!cascade!mxgate!coyoacan!purdue!hkim
From: hkim@purdue.edu (Heather Kim)
Newsgroups: comp.dsp
Subject: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Feb14.221705.4261@purdue.edu>
Date: Mon, 14 Feb 1994 22:17:05 GMT
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Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.

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 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.

-- 
Heather Kim
Opinions expressed are solely my own and not those of Purdue University Engineering Computer Network.
------------------------------------------------------------

From elindqvist@pacbell.net Tue Feb 15 06:41:05 1994
Path: ashpoly!cascade!transat!eunet-fr!teletel!pacbell!elindqvist
From: elindqvist@pacbell.net (Élodie Lindqvist)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Feb15.064105.9212@pacbell.net>
Date: Tue, 15 Feb 1994 06:41:05 GMT
References: <1994Feb14.221705.4261@purdue.edu>
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In article <1994Feb14.221705.4261@purdue.edu>, hkim@purdue.edu (Heather Kim) writes:
> Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.
> 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.

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

-- 
Élodie Lindqvist
Tape trading list upon request. SASE required for international mail.

From lperez@uu.net Wed Feb 16 17:20:05 1994
Path: ashpoly!cascade!transat!eunet-de!hansebox!uu!lperez
From: lperez@uu.net (Lars Pérez)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Feb16.172005.9085@uu.net>
Date: Wed, 16 Feb 1994 17:20:05 GMT
References: <1994Feb14.221705.4261@purdue.edu>
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In article <1994Feb14.221705.4261@purdue.edu>, hkim@purdue.edu (Heather Kim) writes:
> Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.
> 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.

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

PGP Public key available via finger or upon request.

-- 
Lars Pérez -- UUNET Technologies, Falls Church VA
"The carrier frequency does not drift by accident."

From jmacdonald@clari.net Thu Feb 17 06:41:05 1994
Path: ashpoly!cascade!bigsur!clari!jmacdonald
From: jmacdonald@clari.net (Julien MacDonald)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Feb17.064105.8001@clari.net>
Date: Thu, 17 Feb 1994 06:41:05 GMT
References: <1994Feb14.221705.4261@purdue.edu>
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In article <1994Feb14.221705.4261@purdue.edu>, hkim@purdue.edu (Heather Kim) writes:
> Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.
> 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.

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

My 14.4k connection dropped twice trying to fetch this thread. Keep articles concise!

-- 
Julien MacDonald | jmacdonald@clari.net
PGP Key fingerprint: 4CBA BD31 21C8 73C0
"Keep the channels open."