From msmirnov@ox.ac.uk Wed Jun 21 18:57:22 1995 Path: ashpoly!cascade!brgate!saturno!ox!msmirnov From: msmirnov@ox.ac.uk (Morag Smirnov) Newsgroups: comp.dsp Subject: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Jun21.185722.3876@ox.ac.uk> Date: Wed, 21 Jun 1995 18:57:22 GMT Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: WinVN 0.99.5 Lines: 11 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. 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. -- Morag Smirnov Opinions expressed are solely my own and not those of Oxford University Computing Laboratory. ------------------------------------------------------------ From stakahashi@rwth-aachen.de Thu Jun 22 09:17:22 1995 Path: ashpoly!cascade!brgate!saturno!rwth-aachen!stakahashi From: stakahashi@rwth-aachen.de (Steve Takahashi) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Jun22.091722.1537@rwth-aachen.de> Date: Thu, 22 Jun 1995 09:17:22 GMT References: <1995Jun21.185722.3876@ox.ac.uk> Organization: RWTH Aachen Informatik NNTP-Posting-Host: rwth-aachen.de X-Newsreader: NewsWatcher 2.0b24 Lines: 11 In article <1995Jun21.185722.3876@ox.ac.uk>, msmirnov@ox.ac.uk (Morag Smirnov) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 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. Unsubscribe me from this list! (Wait, this is Usenet, never mind). -- Steve Takahashi | stakahashi@rwth-aachen.de PGP Key fingerprint: 473D 2E32 766D 08C3 "Keep the channels open." From leriksson@kth.se Fri Jun 23 13:03:22 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!kth!leriksson From: leriksson@kth.se (Lucia Eriksson) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Jun23.130322.2756@kth.se> Date: Fri, 23 Jun 1995 13:03:22 GMT References: <1995Jun21.185722.3876@ox.ac.uk> <1995Jun22.091722.1537@rwth-aachen.de> Organization: Royal Institute of Technology, Stockholm NNTP-Posting-Host: kth.se X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1995Jun22.091722.1537@rwth-aachen.de>, stakahashi@rwth-aachen.de (Steve Takahashi) 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. If you are posting from AOL, please read RFC 1036 before posting again. -- Lucia Eriksson Tape trading list upon request. SASE required for international mail. From kfournier@stanford.edu Sat Jun 24 05:17:22 1995 Path: ashpoly!cascade!transat!ukc!fennimore!stanford!kfournier From: kfournier@stanford.edu (Katrin Fournier) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Jun24.051722.3960@stanford.edu> Date: Sat, 24 Jun 1995 05:17:22 GMT References: <1995Jun21.185722.3876@ox.ac.uk> Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Jun21.185722.3876@ox.ac.uk>, msmirnov@ox.ac.uk (Morag Smirnov) 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. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- Katrin Fournier "They will send a copy in my place." Sun 3/60 (SunOS 4.1.1) / System 7.5.1