From mmoreno@inria.fr Wed May 15 07:08:16 1996
Path: ashpoly!cascade!transat!ukc!fennimore!inria!mmoreno
From: mmoreno@inria.fr (Mikhail Moreno)
Newsgroups: comp.dsp
Subject: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996May15.070816.5079@inria.fr>
Date: Wed, 15 May 1996 07:08:16 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.
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.

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

-- 
Mikhail Moreno | mmoreno@inria.fr
PGP Key fingerprint: 15F9 AF3B 2A35 385F
"Keep the channels open."

From akowalski@utexas.edu Fri May 17 06:29:16 1996
Path: ashpoly!bigsur!pacrim!krgate!eunha!utexas!akowalski
From: akowalski@utexas.edu (Andrei Kowalski)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1996May17.062916.8103@utexas.edu>
Date: Fri, 17 May 1996 06:29:16 GMT
References: <1996May15.070816.5079@inria.fr>
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In article <1996May15.070816.5079@inria.fr>, mmoreno@inria.fr (Mikhail Moreno) 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.

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.

-- 
=== Andrei Kowalski ===
Dept of Electrical Engineering, University of Texas at Austin
"The carrier frequency does not drift by accident."