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I am trying to plot magnitude against frequency averaged over a time window.

To do this I make a morlet wavelet Filterbank. And multiply the dft of each kernel by the dft of my incoming data set.

I take the mean value for each kernel multiplication result and plot this.

However somewhere along the way I have lost how to convert this to a meaningful scale.

I am using apple accelerate to perform the FFT, and as this does not scale, I divide each result by the sample size.

When I extract the magnitude using mag = sqrt((real^2) + (imag^2)) I am left with an array of very small numbers.

How do I convert this to meaningful magnitude in dB?

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