From jstewart@kth.se Wed Apr 10 09:46:55 1996
Path: ashpoly!cascade!transat!ukc!fennimore!kth!jstewart
From: jstewart@kth.se (Julien Stewart)
Newsgroups: comp.dsp
Subject: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Apr10.094655.7631@kth.se>
Date: Wed, 10 Apr 1996 09:46:55 GMT
Organization: Royal Institute of Technology, Stockholm
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Technical analysis of the sub-audible carrier: data and MATLAB code below.

Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.
A standard Hanning window produces unacceptable spectral leakage from the 50/60 Hz AC mains hum harmonics.

I've uploaded the C source for my decimation and bandpass filter to ftp.ashford-poly.edu.

-- 
Julien Stewart -- Royal Institute of Technology, Stockholm
"Hardware is temporary. The signal survives."

From jramirez@kiae.su Wed Apr 10 13:54:55 1996
Path: ashpoly!cascade!brgate!saturno!kiae!jramirez
From: jramirez@kiae.su (Jen Ramírez)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Apr10.135455.7334@kiae.su>
Date: Wed, 10 Apr 1996 13:54:55 GMT
References: <1996Apr10.094655.7631@kth.se>
Organization: Kurchatov Institute of Atomic Energy, Moscow
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In article <1996Apr10.094655.7631@kth.se>, jstewart@kth.se (Julien Stewart) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.
> Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.

Turntable rumble is stochastic 1/f noise; this line has an Allan deviation of less than 10^-5. It was generated by a quartz crystal clock.

-- 
Jen Ramírez <jramirez@kiae.su>
"Measuring a record you own is listening, not piracy."
Decstation 5000/200 / SunOS 4.1.4

From akang@cmu.edu Thu Apr 11 15:05:55 1996
Path: ashpoly!cascade!transat!ukc!fennimore!cmu!akang
From: akang@cmu.edu (Astrid Kang)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Apr11.150555.1853@cmu.edu>
Date: Thu, 11 Apr 1996 15:05:55 GMT
References: <1996Apr10.094655.7631@kth.se> <1996Apr10.135455.7334@kiae.su>
Organization: Carnegie Mellon University School of CS
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In article <1996Apr10.135455.7334@kiae.su>, jramirez@kiae.su (Jen Ramírez) writes:
> Turntable rumble is stochastic 1/f noise; this line has an Allan deviation of less than 10^-5. It was generated by a quartz crystal clock.

Have you checked your sound card's ADC clock? Cheap Sound Blaster cards use uncalibrated ceramic resonators that drift with temperature.

-- 
Astrid Kang | akang@cmu.edu
PGP Key fingerprint: D655 E923 BCEC 1E7F
"Keep the channels open."

From anilsson@unam.mx Thu Apr 11 21:29:55 1996
Path: ashpoly!cascade!transat!eunet-de!hansebox!unam!anilsson
From: anilsson@unam.mx (Anton Nilsson)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Apr11.212955.3561@unam.mx>
Date: Thu, 11 Apr 1996 21:29:55 GMT
References: <1996Apr10.094655.7631@kth.se>
Organization: Universidad Nacional Autónoma de México (DGSCA)
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In article <1996Apr10.094655.7631@kth.se>, jstewart@kth.se (Julien Stewart) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.

Good work on the windowing. I replicated your result with an 8192-point FFT on a SPARCstation 20. The peak is exactly 14.2003 Hz.

-- 
Anton Nilsson
Tape trading list upon request. SASE required for international mail.