From bhughes@mit.edu Thu Mar 09 12:15:09 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!mit!bhughes From: bhughes@mit.edu (Bruno Hughes) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Mar09.121509.7577@mit.edu> Date: Thu, 09 Mar 1995 12:15:09 GMT Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 10 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. -- Bruno Hughes Tape trading list upon request. SASE required for international mail. From tito@rwth-aachen.de Fri Mar 10 10:47:09 1995 Path: ashpoly!cascade!brgate!saturno!rwth-aachen!tito From: tito@rwth-aachen.de (Thiago Ito) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Mar10.104709.2142@rwth-aachen.de> Date: Fri, 10 Mar 1995 10:47:09 GMT References: <1995Mar09.121509.7577@mit.edu> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Mar09.121509.7577@mit.edu>, bhughes@mit.edu (Bruno Hughes) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Thiago Ito Opinions expressed are solely my own and not those of RWTH Aachen Informatik. ------------------------------------------------------------ From nsantos@demon.co.uk Sat Mar 11 12:36:09 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!demon!nsantos From: nsantos@demon.co.uk (Natalia Santos) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Mar11.123609.5498@demon.co.uk> Date: Sat, 11 Mar 1995 12:36:09 GMT References: <1995Mar09.121509.7577@mit.edu> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Mar09.121509.7577@mit.edu>, bhughes@mit.edu (Bruno Hughes) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Natalia Santos Tape trading list upon request. SASE required for international mail. From jchoi@kiae.su Sun Mar 12 05:55:09 1995 Path: ashpoly!cascade!brgate!saturno!kiae!jchoi From: jchoi@kiae.su (Joachim Choi) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Mar12.055509.6062@kiae.su> Date: Sun, 12 Mar 1995 05:55:09 GMT References: <1995Mar09.121509.7577@mit.edu> <1995Mar10.104709.2142@rwth-aachen.de> Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1995Mar10.104709.2142@rwth-aachen.de>, tito@rwth-aachen.de (Thiago Ito) writes: > Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. 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 Choi *PLONK* filter active for trolls. Sun SparcStation 20 - NetBSD 1.0