File:Comparison of periodogram and Welch methods of spectral density estimation.png

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Summary

Description
English: The power spectral density of a segment of music is estimated by two different methods, for comparison.
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The factual accuracy of this description or the file name is disputed.
Reason: The script below uses the two-sided spectrum, which produces a mirrored copy of the spectrum (from a purely real input signal), which would correctly be plotted at negative frequencies. Falsely, the x-axis goes beyond the Nyquist frequency of 22.5 kHz and places the copy at higher frequencies. Ideally, simply a one-sided spectrum should be used instead.
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Source Own work
Author Bob K
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Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

PNG development
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Octave/gnuplot source
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This graphic was created with the help of the following Octave script: 

graphics_toolkit gnuplot pkg load signal  load 'music.mat'    % adds variables wavedata and samplerate to the workspace whos                % displays the workspace %{music.mat was created by these steps in program Audacity:   • Open a stereo mp3 file.   • Right-click on the filename, and choose Split Stereo to Mono in the drop-down menu.   • Delete one channel.   • Highlight a section to be exported.   • Choose Export Selected Audio.   • Choose Save As Type:  Other Uncompressed Files.   • Under Options, set Header=MAT5 and Encoding=Signed 16-bit PCM %} periodogram (wavedata, [], 512, samplerate, 'twosided') grid on xlim([0 samplerate]) title("Periodogram",'FontSize', 14) xlabel('Frequency (Hz)','FontSize', 14) ylabel('Amplitude (dB)','FontSize', 14)  figure pwelch(wavedata, hann(512), 0.25, 512, samplerate, 'twosided', 'dB') grid on xlim([0 samplerate]) ylim([-60 60]) title("Welch's method",'FontSize', 14) xlabel('Frequency (Hz)','FontSize', 14) ylabel('Amplitude (dB)','FontSize', 14)

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inception

24 October 2016

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image/png

checksum

27b6c67ebef7133ddbdecfd309d07050be4a1602

determination method or standard: SHA-1

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544 pixel

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Date/TimeThumbnailDimensionsUserComment
current20:07, 24 October 2016Thumbnail for version as of 20:07, 24 October 2016544 × 662 (33 KB)Bob KUser created page with UploadWizard

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