From gkang@cam.ac.uk Sun Dec 25 19:55:18 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!cam!gkang From: gkang@cam.ac.uk (Göran Kang) Newsgroups: comp.dsp Subject: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec25.195518.6552@cam.ac.uk> Date: Sun, 25 Dec 1994 19:55:18 GMT Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 10 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. -- Göran Kang -- University of Cambridge Computer Laboratory "A soul is not exclusive to biology." From rnovak@titech.ac.jp Mon Dec 26 21:20:18 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!titech!rnovak From: rnovak@titech.ac.jp (Rodrigo Novak) Newsgroups: comp.dsp Subject: Re: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec26.212018.9766@titech.ac.jp> Date: Mon, 26 Dec 1994 21:20:18 GMT References: <1994Dec25.195518.6552@cam.ac.uk> Organization: Tokyo Institute of Technology Computer Centre NNTP-Posting-Host: titech.ac.jp X-Newsreader: Netscape 1.1N Lines: 10 In article <1994Dec25.195518.6552@cam.ac.uk>, gkang@cam.ac.uk (Göran Kang) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- === Rodrigo Novak === Dept of Electrical Engineering, Tokyo Institute of Technology Computer Centre "In theory there is no difference between theory and practice." From soliveira@pipeline.com Wed Dec 28 05:41:18 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!pipeline!soliveira From: soliveira@pipeline.com (Sun-mi Oliveira) Newsgroups: comp.dsp Subject: Re: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec28.054118.6234@pipeline.com> Date: Wed, 28 Dec 1994 05:41:18 GMT References: <1994Dec25.195518.6552@cam.ac.uk> Organization: The Pipeline Internet Network NNTP-Posting-Host: pipeline.com X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1994Dec25.195518.6552@cam.ac.uk>, gkang@cam.ac.uk (Göran Kang) 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. -- Sun-mi Oliveira -- The Pipeline Internet Network "Do not worship the copy." From pmuller@stanford.edu Thu Dec 29 18:13:18 1994 Path: ashpoly!cascade!brgate!saturno!stanford!pmuller From: pmuller@stanford.edu (Pavel Müller) Newsgroups: comp.dsp Subject: Re: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec29.181318.9019@stanford.edu> Date: Thu, 29 Dec 1994 18:13:18 GMT References: <1994Dec25.195518.6552@cam.ac.uk> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: Netscape 1.1N Lines: 10 In article <1994Dec25.195518.6552@cam.ac.uk>, gkang@cam.ac.uk (Göran Kang) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Pavel Müller Tape trading list upon request. SASE required for international mail. From vrodriguez@uu.net Sat Dec 31 19:30:18 1994 Path: ashpoly!bigsur!pacrim!jpgate!kamome!uu!vrodriguez From: vrodriguez@uu.net (Valeria Rodríguez) Newsgroups: comp.dsp Subject: Re: [FLAME] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec31.193018.5020@uu.net> Date: Sat, 31 Dec 1994 19:30:18 GMT References: <1994Dec25.195518.6552@cam.ac.uk> <1994Dec26.212018.9766@titech.ac.jp> Organization: UUNET Technologies, Falls Church VA NNTP-Posting-Host: uu.net X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1994Dec26.212018.9766@titech.ac.jp>, rnovak@titech.ac.jp (Rodrigo Novak) 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. -- Valeria Rodríguez *PLONK* filter active for trolls. Amiga 1200 (Blizzard 030/50) - NetBSD 1.0