From mokonkwo@illinois.edu Mon Aug 08 10:54:39 1994
Path: ashpoly!bigsur!pacrim!krgate!eunha!illinois!mokonkwo
From: mokonkwo@illinois.edu (Matthias Okonkwo)
Newsgroups: comp.dsp
Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Aug08.105439.5393@illinois.edu>
Date: Mon, 08 Aug 1994 10:54:39 GMT
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Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.

A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor.
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.

-- 
Matthias Okonkwo -- University of Illinois Urbana-Champaign
"They will send a copy in my place."

From rnakamura@pipeline.com Mon Aug 08 19:10:39 1994
Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!pipeline!rnakamura
From: rnakamura@pipeline.com (Rodrigo Nakamura)
Newsgroups: comp.dsp
Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Aug08.191039.9145@pipeline.com>
Date: Mon, 08 Aug 1994 19:10:39 GMT
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In article <1994Aug08.105439.5393@illinois.edu>, mokonkwo@illinois.edu (Matthias Okonkwo) writes:
> Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.

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

-- 
Rodrigo Nakamura | rnakamura@pipeline.com
PGP Key fingerprint: 1C01 061D 46AD 2719
"Keep the channels open."

From amacdonald@purdue.edu Wed Aug 10 05:09:39 1994
Path: ashpoly!cascade!transat!eunet-fr!teletel!purdue!amacdonald
From: amacdonald@purdue.edu (Astrid MacDonald)
Newsgroups: comp.dsp
Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Aug10.050939.8612@purdue.edu>
Date: Wed, 10 Aug 1994 05:09:39 GMT
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In article <1994Aug08.105439.5393@illinois.edu>, mokonkwo@illinois.edu (Matthias Okonkwo) writes:
> Comparing window sidelobe attenuation on 16-bit 44.1 kHz WAV files.

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

-- 
Astrid MacDonald
Opinions expressed are solely my own and not those of Purdue University Engineering Computer Network.
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From slindqvist@clari.net Thu Aug 11 16:55:39 1994
Path: ashpoly!bigsur!pacrim!jpgate!kamome!clari!slindqvist
From: slindqvist@clari.net (Sven Lindqvist)
Newsgroups: comp.dsp
Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1994Aug11.165539.3820@clari.net>
Date: Thu, 11 Aug 1994 16:55:39 GMT
References: <1994Aug08.105439.5393@illinois.edu> <1994Aug10.050939.8612@purdue.edu>
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In article <1994Aug10.050939.8612@purdue.edu>, amacdonald@purdue.edu (Astrid MacDonald) 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.

Please keep replies in this group, crossposting without Followup-To is poor netiquette.

-- 
Sven Lindqvist
Opinions expressed are solely my own and not those of ClariNet Communications Corp.
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