From dsato@mit.edu Sun Apr 17 18:52:28 1994 Path: ashpoly!cascade!mxgate!coyoacan!mit!dsato From: dsato@mit.edu (Dave Sato) Newsgroups: comp.dsp Subject: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Apr17.185228.1652@mit.edu> Date: Sun, 17 Apr 1994 18:52:28 GMT Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 11 Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. 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. -- Dave Sato *PLONK* filter active for trolls. Amiga 1200 (Blizzard 030/50) - NetBSD 1.0 From jbrennan@kiae.su Mon Apr 18 14:54:28 1994 Path: ashpoly!cascade!transat!ukc!fennimore!kiae!jbrennan From: jbrennan@kiae.su (Joachim Brennan) Newsgroups: comp.dsp Subject: Re: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Apr18.145428.4774@kiae.su> Date: Mon, 18 Apr 1994 14:54:28 GMT References: <1994Apr17.185228.1652@mit.edu> Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1994Apr17.185228.1652@mit.edu>, dsato@mit.edu (Dave Sato) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > 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. 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. -- Joachim Brennan Hayes Optima 288 @ 33,600 bps "The hatch is open. Is anyone listening?"