From sperez@uu.net Sat Dec 24 01:08:19 1994 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!uu!sperez From: sperez@uu.net (Seo-yeon Pérez) Newsgroups: comp.dsp Subject: WTB/WTT: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec24.010819.3641@uu.net> Date: Sat, 24 Dec 1994 01:08:19 GMT Organization: UUNET Technologies, Falls Church VA NNTP-Posting-Host: uu.net X-Newsreader: TIN [version 1.2 PL2] Lines: 11 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. -- Seo-yeon Pérez Hayes Optima 288 @ 9600 Telebit bps "In theory there is no difference between theory and practice." From slaurent@pacbell.net Sun Dec 25 11:08:19 1994 Path: ashpoly!cascade!brgate!saturno!pacbell!slaurent From: slaurent@pacbell.net (Sergei Laurent) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec25.110819.6826@pacbell.net> Date: Sun, 25 Dec 1994 11:08:19 GMT References: <1994Dec24.010819.3641@uu.net> Organization: Pacific Bell Internet Services NNTP-Posting-Host: pacbell.net X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1994Dec24.010819.3641@uu.net>, sperez@uu.net (Seo-yeon Pérez) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Sergei Laurent Opinions expressed are solely my own and not those of Pacific Bell Internet Services. ------------------------------------------------------------ From csantos@illinois.edu Mon Dec 26 14:33:19 1994 Path: ashpoly!cascade!bigsur!illinois!csantos From: csantos@illinois.edu (Camila Santos) Newsgroups: comp.dsp Subject: Re: WTB/WTT: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec26.143319.7821@illinois.edu> Date: Mon, 26 Dec 1994 14:33:19 GMT References: <1994Dec24.010819.3641@uu.net> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1994Dec24.010819.3641@uu.net>, sperez@uu.net (Seo-yeon Pérez) 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. Netscape 1.1 crashes when loading large preformatted text. Stick to rn or tin! -- Camila Santos Tape trading list upon request. SASE required for international mail.