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I am working on a spectrogram project and trying to plot the frequencies with the highest magnitude at each section. We have tested and recorded the do-re-mi-fa-so-la-ti-do sang by a human. After plotting the spectrogram, we have seen multiple sets of increase in magnitudes. In this image , we have encircled our ideal frequencies to be plotted.

image

However, there were some sections that had the frequencies with the highest magnitude located outside our ideal set of frequencies. For example, in time 6-7, the frequency plotted was around 200 instead of 400.

Do anybody have an idea why this happens?

bytecode77
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user3286528
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  • You need to do proper pitch detection, not just pick a random harmonic. Check out the Harmonic Product Spectrum method. – Paul R Apr 21 '15 at 11:57

1 Answers1

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This is normal and expected. The overtone or harmonic with the highest magnitude in speech or singing can vary with the pitch and voicing (the particular vowel sound, etc.) Change the speaker, pitch or vowel and the overtone or harmonic frequency multiplier for the highest energy peak can change. It can even change over time for a constant vowel and pitch.

hotpaw2
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