Theoretical: Why use trapz to calculate absolute power?

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Eric 2015-3-31

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回答： Vinod Sudheesh 2015-4-1

Hi everybody,

This more of a theoretical question and since I'm not an engineer I apologize in advance for any trouble understanding my question. I've recently seen a script that first calculated the power using pwelch method and then used trapz to calculate the integral between two frequency bins, like:

[Pxx W] = pwelch(data, window, overlap);
Pow1 =  [Pow1 ; trapz(Pxx(2:6))];

Does anyone know the possible reason to take the integral of the frequencies when you are interested in power? And does this represent something different?

Thanks,

Eric

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Answer 1

Vinod Sudheesh 2015-4-1

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The "pwelch" function returns the power spectral density (PSD) estimate. To compute the power contained in a frequency range, the PSD should be integrated over the required frequency range.