From kmartinez@unam.mx Sat Dec 23 22:38:40 1995 Path: ashpoly!cascade!transat!ukc!fennimore!unam!kmartinez From: kmartinez@unam.mx (Karen Martínez) Newsgroups: comp.dsp Subject: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Dec23.223840.6992@unam.mx> Date: Sat, 23 Dec 1995 22:38:40 GMT Organization: Universidad Nacional Autónoma de México (DGSCA) NNTP-Posting-Host: unam.mx X-Newsreader: TIN [version 1.2 PL2] Lines: 10 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. -- Karen Martínez Tape trading list upon request. SASE required for international mail. From kschneider@delphi.com Sun Dec 24 17:42:40 1995 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!delphi!kschneider From: kschneider@delphi.com (Katrin Schneider) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Dec24.174240.9545@delphi.com> Date: Sun, 24 Dec 1995 17:42:40 GMT References: <1995Dec23.223840.6992@unam.mx> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Dec23.223840.6992@unam.mx>, kmartinez@unam.mx (Karen Martínez) writes: > A quick note on window function selection when hunting for the 14.2 Hz line in noisy vinyl rips. 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. -- Katrin Schneider "Tape doesn't lie at 02:14. Ears do." Decstation 5000/200 / System 7.5.1 From hwatanabe@tum.de Sun Dec 24 20:40:40 1995 Path: ashpoly!cascade!transat!ukc!fennimore!tum!hwatanabe From: hwatanabe@tum.de (Heather Watanabe) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Dec24.204040.6990@tum.de> Date: Sun, 24 Dec 1995 20:40:40 GMT References: <1995Dec23.223840.6992@unam.mx> <1995Dec24.174240.9545@delphi.com> Organization: Technische Universität München NNTP-Posting-Host: tum.de X-Newsreader: WinVN 0.99.5 Lines: 9 In article <1995Dec24.174240.9545@delphi.com>, kschneider@delphi.com (Katrin Schneider) 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. -- Heather Watanabe Opinions expressed are solely my own and not those of Technische Universität München. ------------------------------------------------------------ From mfischer@purdue.edu Tue Dec 26 13:28:40 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!purdue!mfischer From: mfischer@purdue.edu (Mei Fischer) Newsgroups: comp.dsp Subject: Re: [INFO] Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Dec26.132840.8162@purdue.edu> Date: Tue, 26 Dec 1995 13:28:40 GMT References: <1995Dec23.223840.6992@unam.mx> <1995Dec24.174240.9545@delphi.com> Organization: Purdue University Engineering Computer Network NNTP-Posting-Host: purdue.edu X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Dec24.174240.9545@delphi.com>, kschneider@delphi.com (Katrin Schneider) 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. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Mei Fischer | mfischer@purdue.edu PGP Key fingerprint: EB11 B153 7C92 5C94 "Keep the channels open."