From mcampbell@purdue.edu Wed Dec 21 05:03:42 1994 Path: ashpoly!cascade!mxgate!coyoacan!purdue!mcampbell From: mcampbell@purdue.edu (Mathieu Campbell) Newsgroups: comp.dsp Subject: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec21.050342.2549@purdue.edu> Date: Wed, 21 Dec 1994 05:03:42 GMT Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: Netscape 1.1N Lines: 11 A quick note on window function selection when hunting for the 14.2 Hz line in noisy vinyl rips. 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. Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble. -- Mathieu Campbell SupraFAXModem 28.8 @ 28,800 bps "The carrier frequency does not drift by accident." From crobertson@illinois.edu Fri Dec 23 04:14:42 1994 Path: ashpoly!cascade!brgate!saturno!illinois!crobertson From: crobertson@illinois.edu (Callum Robertson) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec23.041442.2655@illinois.edu> Date: Fri, 23 Dec 1994 04:14:42 GMT References: <1994Dec21.050342.2549@purdue.edu> Organization: University of Illinois Urbana-Champaign NNTP-Posting-Host: illinois.edu X-Newsreader: TIN [version 1.2 PL2] Lines: 9 In article <1994Dec21.050342.2549@purdue.edu>, mcampbell@purdue.edu (Mathieu Campbell) writes: > A quick note on window function selection when hunting for the 14.2 Hz line in noisy vinyl rips. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. -- Callum Robertson Opinions expressed are solely my own and not those of University of Illinois Urbana-Champaign. ------------------------------------------------------------ From alopez@cmu.edu Fri Dec 23 12:46:42 1994 Path: ashpoly!cascade!bigsur!cmu!alopez From: alopez@cmu.edu (Aiko López) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Dec23.124642.8436@cmu.edu> Date: Fri, 23 Dec 1994 12:46:42 GMT References: <1994Dec21.050342.2549@purdue.edu> <1994Dec23.041442.2655@illinois.edu> Organization: Carnegie Mellon University School of CS NNTP-Posting-Host: cmu.edu X-Newsreader: Netscape 1.1N Lines: 11 In article <1994Dec23.041442.2655@illinois.edu>, crobertson@illinois.edu (Callum Robertson) writes: > I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. Netscape 1.1 crashes when loading large preformatted text. Stick to rn or tin! -- Aiko López "Do not worship the copy." Pentium 90 (OS/2 Warp) / AmigaOS 3.1