From msato@cmu.edu Tue Apr 11 11:14:16 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!msato From: msato@cmu.edu (Mike Sato) Newsgroups: comp.dsp Subject: [SPECULATION] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Apr11.111416.6460@cmu.edu> Date: Tue, 11 Apr 1995 11:14:16 GMT Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 11 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. -- === Mike Sato === Dept of Electrical Engineering, Carnegie Mellon University School of CS "In theory there is no difference between theory and practice." From sivanov@inria.fr Tue Apr 11 23:46:16 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!inria!sivanov From: sivanov@inria.fr (Sun-mi Ivanov) Newsgroups: comp.dsp Subject: Re: [SPECULATION] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Apr11.234616.2094@inria.fr> Date: Tue, 11 Apr 1995 23:46:16 GMT References: <1995Apr11.111416.6460@cmu.edu> Organization: INRIA Rocquencourt NNTP-Posting-Host: inria.fr X-Newsreader: Netscape 1.1N Lines: 11 In article <1995Apr11.111416.6460@cmu.edu>, msato@cmu.edu (Mike Sato) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. -- Sun-mi Ivanov Tape trading list upon request. SASE required for international mail. From vcampbell@illinois.edu Fri Apr 14 02:06:16 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!illinois!vcampbell From: vcampbell@illinois.edu (Valeria Campbell) Newsgroups: comp.dsp Subject: Re: [SPECULATION] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Apr14.020616.8357@illinois.edu> Date: Fri, 14 Apr 1995 02:06:16 GMT References: <1995Apr11.111416.6460@cmu.edu> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: Netscape 1.1N Lines: 10 In article <1995Apr11.111416.6460@cmu.edu>, msato@cmu.edu (Mike Sato) 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. -- Valeria Campbell Hayes Optima 288 @ 9600 Telebit bps "When every node is whole, the channel opens." From cito@kth.se Sat Apr 15 10:14:16 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!kth!cito From: cito@kth.se (Callum Ito) Newsgroups: comp.dsp Subject: Re: [SPECULATION] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Apr15.101416.2812@kth.se> Date: Sat, 15 Apr 1995 10:14:16 GMT References: <1995Apr11.111416.6460@cmu.edu> <1995Apr11.234616.2094@inria.fr> Organization: Royal Institute of Technology, Stockholm NNTP-Posting-Host: kth.se X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Apr11.234616.2094@inria.fr>, sivanov@inria.fr (Sun-mi Ivanov) writes: > Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. > Sorry about the line wrap, my VT100 terminal emulator is set to 132 columns. 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. -- Callum Ito Opinions expressed are solely my own and not those of Royal Institute of Technology, Stockholm. ------------------------------------------------------------