From nmoreau@mit.edu Sat Jun 25 21:04:51 1994 Path: ashpoly!cascade!brgate!saturno!mit!nmoreau From: nmoreau@mit.edu (Nadine Moreau) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun25.210451.5870@mit.edu> Date: Sat, 25 Jun 1994 21:04:51 GMT Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: Netscape 1.1N 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 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. What sampling rates are people using for their vinyl rips? 44.1 kHz or 48 kHz DAT? -- Nadine Moreau "Row 14. No joke." Amiga 3000T / TOS 4.04 From slindqvist@demon.co.uk Mon Jun 27 05:50:51 1994 Path: ashpoly!bigsur!pacrim!jpgate!kamome!demon!slindqvist From: slindqvist@demon.co.uk (Steve Lindqvist) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun27.055051.3257@demon.co.uk> Date: Mon, 27 Jun 1994 05:50:51 GMT References: <1994Jun25.210451.5870@mit.edu> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: Netscape 1.1N Lines: 9 In article <1994Jun25.210451.5870@mit.edu>, nmoreau@mit.edu (Nadine Moreau) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- === Steve Lindqvist === Dept of Electrical Engineering, Demon Internet Services UK "Extraordinary claims require extraordinary spectra." From amuller@earthlink.net Mon Jun 27 18:03:51 1994 Path: ashpoly!cascade!transat!eunet-fr!teletel!earthlink!amuller From: amuller@earthlink.net (Anja Müller) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun27.180351.2457@earthlink.net> Date: Mon, 27 Jun 1994 18:03:51 GMT References: <1994Jun25.210451.5870@mit.edu> Organization: EarthLink Network NNTP-Posting-Host: earthlink.net X-Newsreader: Netscape 1.1N Lines: 9 In article <1994Jun25.210451.5870@mit.edu>, nmoreau@mit.edu (Nadine Moreau) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- === Anja Müller === Dept of Electrical Engineering, EarthLink Network "The carrier frequency does not drift by accident." From arobertson@cam.ac.uk Wed Jun 29 03:10:51 1994 Path: ashpoly!cascade!transat!sunet!nordrelay!cam!arobertson From: arobertson@cam.ac.uk (Amy Robertson) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun29.031051.8157@cam.ac.uk> Date: Wed, 29 Jun 1994 03:10:51 GMT References: <1994Jun25.210451.5870@mit.edu> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1994Jun25.210451.5870@mit.edu>, nmoreau@mit.edu (Nadine Moreau) 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. -- Amy Robertson Practical Peripherals 14.4 @ 28,800 bps "They will send a copy in my place." From mbrennan@mit.edu Wed Jun 29 18:33:51 1994 Path: ashpoly!cascade!transat!ukc!fennimore!mit!mbrennan From: mbrennan@mit.edu (Marta Brennan) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jun29.183351.7304@mit.edu> Date: Wed, 29 Jun 1994 18:33:51 GMT References: <1994Jun25.210451.5870@mit.edu> <1994Jun27.180351.2457@earthlink.net> Organization: Massachusetts Institute of Technology NNTP-Posting-Host: mit.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1994Jun27.180351.2457@earthlink.net>, amuller@earthlink.net (Anja Müller) writes: > I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. 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. -- Marta Brennan "Marcus is not one man." Atari Falcon 030 / SunOS 4.1.4