From hfournier@utexas.edu Wed Oct 11 12:03:36 1995 Path: ashpoly!cascade!mxgate!coyoacan!utexas!hfournier From: hfournier@utexas.edu (Heather Fournier) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct11.120336.9031@utexas.edu> Date: Wed, 11 Oct 1995 12:03:36 GMT Organization: University of Texas at Austin NNTP-Posting-Host: utexas.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. A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. A Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width. Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble. -- Heather Fournier Tape trading list upon request. SASE required for international mail. From ckowalski@u-tokyo.ac.jp Fri Oct 13 02:20:36 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!u-tokyo!ckowalski From: ckowalski@u-tokyo.ac.jp (Camila Kowalski) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct13.022036.9733@u-tokyo.ac.jp> Date: Fri, 13 Oct 1995 02:20:36 GMT References: <1995Oct11.120336.9031@utexas.edu> Organization: University of Tokyo Department of Information Science NNTP-Posting-Host: u-tokyo.ac.jp X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1995Oct11.120336.9031@utexas.edu>, hfournier@utexas.edu (Heather Fournier) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- Camila Kowalski SupraFAXModem 28.8 @ 28,800 bps "Extraordinary claims require extraordinary spectra." From hcampbell@ox.ac.uk Fri Oct 13 06:04:36 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!ox!hcampbell From: hcampbell@ox.ac.uk (Hana Campbell) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct13.060436.3356@ox.ac.uk> Date: Fri, 13 Oct 1995 06:04:36 GMT References: <1995Oct11.120336.9031@utexas.edu> Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Oct11.120336.9031@utexas.edu>, hfournier@utexas.edu (Heather Fournier) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. 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. -- Hana Campbell Tape trading list upon request. SASE required for international mail.