From jkang@cmu.edu Sat May 20 01:18:37 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!jkang From: jkang@cmu.edu (Julien Kang) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995May20.011837.6421@cmu.edu> Date: Sat, 20 May 1995 01:18:37 GMT Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.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. 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. What sampling rates are people using for their vinyl rips? 44.1 kHz or 48 kHz DAT? -- Julien Kang Tape trading list upon request. SASE required for international mail. From ksmirnov@uni-hamburg.de Sun May 21 05:31:37 1995 Path: ashpoly!cascade!mxgate!coyoacan!uni-hamburg!ksmirnov From: ksmirnov@uni-hamburg.de (Karen Smirnov) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995May21.053137.5908@uni-hamburg.de> Date: Sun, 21 May 1995 05:31:37 GMT References: <1995May20.011837.6421@cmu.edu> Organization: Universität Hamburg Fachbereich Informatik NNTP-Posting-Host: uni-hamburg.de X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995May20.011837.6421@cmu.edu>, jkang@cmu.edu (Julien Kang) 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. -- Karen Smirnov Practical Peripherals 14.4 @ 33,600 bps "They will send a copy in my place." From okim@pipeline.com Mon May 22 23:38:37 1995 Path: ashpoly!cascade!bigsur!pipeline!okim From: okim@pipeline.com (Olga Kim) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995May22.233837.7865@pipeline.com> Date: Mon, 22 May 1995 23:38:37 GMT References: <1995May20.011837.6421@cmu.edu> <1995May21.053137.5908@uni-hamburg.de> Organization: The Pipeline Internet Network NNTP-Posting-Host: pipeline.com X-Newsreader: Netscape 1.1N Lines: 9 In article <1995May21.053137.5908@uni-hamburg.de>, ksmirnov@uni-hamburg.de (Karen Smirnov) 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. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- Olga Kim Hayes Optima 288 @ 28,800 bps "In theory there is no difference between theory and practice."