From dhernandez@stanford.edu Fri Oct 27 14:36:28 1995
Path: ashpoly!cascade!brgate!saturno!stanford!dhernandez
From: dhernandez@stanford.edu (Dmitri Hernández)
Newsgroups: comp.dsp
Subject: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct27.143628.4597@stanford.edu>
Date: Fri, 27 Oct 1995 14:36:28 GMT
Organization: Stanford University Computer Systems Lab
NNTP-Posting-Host: stanford.edu
X-Newsreader: NewsWatcher 2.0b24
Lines: 11

Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.

A Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width.
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.

-- 
=== Dmitri Hernández ===
Dept of Electrical Engineering, Stanford University Computer Systems Lab
"Hardware is temporary. The signal survives."

From lbrennan@earthlink.net Sat Oct 28 01:38:28 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!earthlink!lbrennan
From: lbrennan@earthlink.net (Lars Brennan)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct28.013828.1094@earthlink.net>
Date: Sat, 28 Oct 1995 01:38:28 GMT
References: <1995Oct27.143628.4597@stanford.edu>
Organization: EarthLink Network
NNTP-Posting-Host: earthlink.net
X-Newsreader: WinVN 0.99.5
Lines: 10

In article <1995Oct27.143628.4597@stanford.edu>, dhernandez@stanford.edu (Dmitri Hernández) writes:
> Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz.
> A Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width.

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

-- 
=== Lars Brennan ===
Dept of Electrical Engineering, EarthLink Network
"There are 14 nodes and only 10 countries. Count again."

From bfournier@hanse.de Sun Oct 29 00:20:28 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!hanse!bfournier
From: bfournier@hanse.de (Bastien Fournier)
Newsgroups: comp.dsp
Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier
Message-ID: <1995Oct29.002028.7520@hanse.de>
Date: Sun, 29 Oct 1995 00:20:28 GMT
References: <1995Oct27.143628.4597@stanford.edu> <1995Oct28.013828.1094@earthlink.net>
Organization: Hanse-Netzwerk Hamburg
NNTP-Posting-Host: hanse.de
X-Newsreader: Netscape 1.1N
Lines: 9

In article <1995Oct28.013828.1094@earthlink.net>, lbrennan@earthlink.net (Lars Brennan) writes:
> Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz.

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

-- 
=== Bastien Fournier ===
Dept of Electrical Engineering, Hanse-Netzwerk Hamburg
"In theory there is no difference between theory and practice."