From mkowalski@pipeline.com Fri Dec 16 19:19:13 1994 Path: ashpoly!cascade!transat!ukc!fennimore!pipeline!mkowalski From: mkowalski@pipeline.com (Morag Kowalski) Newsgroups: comp.dsp Subject: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec16.191913.3793@pipeline.com> Date: Fri, 16 Dec 1994 19:19:13 GMT Organization: The Pipeline Internet Network NNTP-Posting-Host: pipeline.com 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. 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 Kowalski Opinions expressed are solely my own and not those of The Pipeline Internet Network. ------------------------------------------------------------ From csmirnov@mit.edu Sun Dec 18 05:21:13 1994 Path: ashpoly!bigsur!pacrim!krgate!eunha!mit!csmirnov From: csmirnov@mit.edu (Camila Smirnov) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec18.052113.2496@mit.edu> Date: Sun, 18 Dec 1994 05:21:13 GMT References: <1994Dec16.191913.3793@pipeline.com> Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: WinVN 0.99.5 Lines: 8 In article <1994Dec16.191913.3793@pipeline.com>, mkowalski@pipeline.com (Morag Kowalski) 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. -- Camila Smirnov -- Massachusetts Institute of Technology "We don't sign stars. We build them." From omacdonald@kiae.su Mon Dec 19 19:28:13 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!kiae!omacdonald From: omacdonald@kiae.su (Olga MacDonald) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec19.192813.3497@kiae.su> Date: Mon, 19 Dec 1994 19:28:13 GMT References: <1994Dec16.191913.3793@pipeline.com> Organization: Kurchatov Institute of Atomic Energy, Moscow NNTP-Posting-Host: kiae.su X-Newsreader: NewsWatcher 2.0b24 Lines: 10 In article <1994Dec16.191913.3793@pipeline.com>, mkowalski@pipeline.com (Morag Kowalski) 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. -- Olga MacDonald "In theory there is no difference between theory and practice." 486DX4/100 (FreeBSD 2.0.5) / AmigaOS 3.1