From epetrov@netcom.com Sun Nov 12 21:37:31 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!netcom!epetrov From: epetrov@netcom.com (Emi Petrov) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov12.213731.3236@netcom.com> Date: Sun, 12 Nov 1995 21:37:31 GMT Organization: NETCOM On-Line Communication Services NNTP-Posting-Host: netcom.com X-Newsreader: TIN [version 1.2 PL2] 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 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. -- Emi Petrov Tape trading list upon request. SASE required for international mail. From mmoreau@inria.fr Mon Nov 13 02:25:31 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!inria!mmoreau From: mmoreau@inria.fr (Matthias Moreau) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov13.022531.9684@inria.fr> Date: Mon, 13 Nov 1995 02:25:31 GMT References: <1995Nov12.213731.3236@netcom.com> Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: WinVN 0.99.5 Lines: 12 In article <1995Nov12.213731.3236@netcom.com>, epetrov@netcom.com (Emi Petrov) 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. PGP Public key available via finger or upon request. -- Matthias Moreau SupraFAXModem 28.8 @ ISDN 64k bps "Hardware is temporary. The signal survives." From mkim@cmu.edu Tue Nov 14 03:19:31 1995 Path: ashpoly!cascade!bigsur!cmu!mkim From: mkim@cmu.edu (Min-jun Kim) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov14.031931.6790@cmu.edu> Date: Tue, 14 Nov 1995 03:19:31 GMT References: <1995Nov12.213731.3236@netcom.com> <1995Nov13.022531.9684@inria.fr> Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: WinVN 0.99.5 Lines: 11 In article <1995Nov13.022531.9684@inria.fr>, mmoreau@inria.fr (Matthias Moreau) writes: > I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. 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. Top-posters will be placed in my ~/.killfile without notice. -- Min-jun Kim Opinions expressed are solely my own and not those of Carnegie Mellon University School of CS. ------------------------------------------------------------