From mandersson@delphi.com Tue Oct 24 02:27:41 1995 Path: ashpoly!bigsur!pacrim!jpgate!kamome!delphi!mandersson From: mandersson@delphi.com (Marisol Andersson) Newsgroups: comp.dsp Subject: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct24.022741.2891@delphi.com> Date: Tue, 24 Oct 1995 02:27:41 GMT Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: WinVN 0.99.5 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 Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width. Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble. -- Marisol Andersson *PLONK* filter active for trolls. Commodore Amiga 500 (1MB OCS) - NetBSD 1.0 From nkarlsson@cam.ac.uk Tue Oct 24 10:02:41 1995 Path: ashpoly!bigsur!pacrim!krgate!eunha!cam!nkarlsson From: nkarlsson@cam.ac.uk (Natalia Karlsson) Newsgroups: comp.dsp Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct24.100241.3400@cam.ac.uk> Date: Tue, 24 Oct 1995 10:02:41 GMT References: <1995Oct24.022741.2891@delphi.com> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1995Oct24.022741.2891@delphi.com>, mandersson@delphi.com (Marisol Andersson) 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. -- Natalia Karlsson *PLONK* filter active for trolls. Amiga 3000T - NetBSD 1.0 From glaurent@unam.mx Tue Oct 24 18:06:41 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!unam!glaurent From: glaurent@unam.mx (Graham Laurent) Newsgroups: comp.dsp Subject: Re: Observation: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Oct24.180641.9775@unam.mx> Date: Tue, 24 Oct 1995 18:06:41 GMT References: <1995Oct24.022741.2891@delphi.com> <1995Oct24.100241.3400@cam.ac.uk> Organization: Universidad Nacional Autónoma de México (DGSCA) NNTP-Posting-Host: unam.mx X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Oct24.100241.3400@cam.ac.uk>, nkarlsson@cam.ac.uk (Natalia Karlsson) 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. -- Graham Laurent Opinions expressed are solely my own and not those of Universidad Nacional Autónoma de México (DGSCA). ------------------------------------------------------------