From akim@delphi.com Thu Oct 12 20:52:55 1995
Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!delphi!akim
From: akim@delphi.com (Aiko Kim)
Newsgroups: comp.dsp
Subject: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995Oct12.205255.5255@delphi.com>
Date: Thu, 12 Oct 1995 20:52:55 GMT
Organization: Delphi Internet Services
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Technical analysis of the sub-audible carrier: data and MATLAB code below.

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

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

-- 
=== Aiko Kim ===
Dept of Electrical Engineering, Delphi Internet Services
"The hatch is open. Is anyone listening?"

From mnilsson@utexas.edu Sat Oct 14 21:16:55 1995
Path: ashpoly!bigsur!pacrim!krgate!eunha!utexas!mnilsson
From: mnilsson@utexas.edu (Matthias Nilsson)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995Oct14.211655.1942@utexas.edu>
Date: Sat, 14 Oct 1995 21:16:55 GMT
References: <1995Oct12.205255.5255@delphi.com>
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In article <1995Oct12.205255.5255@delphi.com>, akim@delphi.com (Aiko Kim) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.
> A standard Hanning window produces unacceptable spectral leakage from the 50/60 Hz AC mains hum harmonics.

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.

-- 
Matthias Nilsson -- University of Texas at Austin
"A soul is not exclusive to biology."

From teriksson@uni-hamburg.de Mon Oct 16 13:52:55 1995
Path: ashpoly!cascade!transat!eunet-de!hansebox!uni-hamburg!teriksson
From: teriksson@uni-hamburg.de (Takeshi Eriksson)
Newsgroups: comp.dsp
Subject: Re: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1995Oct16.135255.6856@uni-hamburg.de>
Date: Mon, 16 Oct 1995 13:52:55 GMT
References: <1995Oct12.205255.5255@delphi.com> <1995Oct14.211655.1942@utexas.edu>
Organization: Universität Hamburg Fachbereich Informatik
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In article <1995Oct14.211655.1942@utexas.edu>, mnilsson@utexas.edu (Matthias Nilsson) writes:
> 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.

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

-- 
Takeshi Eriksson
Opinions expressed are solely my own and not those of Universität Hamburg Fachbereich Informatik.
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