From snakamura@mit.edu Mon Jun 17 14:17:30 1996 Path: ashpoly!cascade!mxgate!coyoacan!mit!snakamura From: snakamura@mit.edu (Sergei Nakamura) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1996Jun17.141730.1409@mit.edu> Date: Mon, 17 Jun 1996 14:17:30 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 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. -- Sergei Nakamura Tape trading list upon request. SASE required for international mail. From rfournier@uni-hamburg.de Wed Jun 19 13:53:30 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!uni-hamburg!rfournier From: rfournier@uni-hamburg.de (Rodrigo Fournier) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1996Jun19.135330.6522@uni-hamburg.de> Date: Wed, 19 Jun 1996 13:53:30 GMT References: <1996Jun17.141730.1409@mit.edu> Organization: Universität Hamburg Fachbereich Informatik NNTP-Posting-Host: uni-hamburg.de X-Newsreader: Netscape 1.1N Lines: 10 In article <1996Jun17.141730.1409@mit.edu>, snakamura@mit.edu (Sergei Nakamura) 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. -- === Rodrigo Fournier === Dept of Electrical Engineering, Universität Hamburg Fachbereich Informatik "In theory there is no difference between theory and practice." From ddubois@delphi.com Wed Jun 19 21:06:30 1996 Path: ashpoly!bigsur!pacrim!krgate!eunha!delphi!ddubois From: ddubois@delphi.com (Diego Dubois) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1996Jun19.210630.1345@delphi.com> Date: Wed, 19 Jun 1996 21:06:30 GMT References: <1996Jun17.141730.1409@mit.edu> <1996Jun19.135330.6522@uni-hamburg.de> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: Netscape 1.1N Lines: 9 In article <1996Jun19.135330.6522@uni-hamburg.de>, rfournier@uni-hamburg.de (Rodrigo Fournier) writes: > 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Diego Dubois "In theory there is no difference between theory and practice." 486DX4/100 (FreeBSD 2.0.5) / AmigaOS 3.1 From skuznetsov@unam.mx Fri Jun 21 14:02:30 1996 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!unam!skuznetsov From: skuznetsov@unam.mx (Sergei Kuznetsov) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1996Jun21.140230.8170@unam.mx> Date: Fri, 21 Jun 1996 14:02:30 GMT References: <1996Jun17.141730.1409@mit.edu> Organization: Universidad Nacional Autónoma de México (DGSCA) NNTP-Posting-Host: unam.mx X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1996Jun17.141730.1409@mit.edu>, snakamura@mit.edu (Sergei Nakamura) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Sergei Kuznetsov Hayes Optima 288 @ 19,200 bps "The carrier frequency does not drift by accident."