What is the default normalization in plot of stft function in Short-time Fourier transform

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I was using matlab to plot Short-time Fourier transform (STFT).
My code was as follows:
[y,Fs] = audioread('p226_001.wav');
a = downsample(y,3);
stft(a,16000,'Window',hanning(512),'OverlapLength',128,'FFTLength',512);
It returned the following plot
The I plotted the origional values using the following code
[y,Fs] = audioread('p226_001.wav');
a = downsample(y,3);
[s, f, t] = stft(a,16000,'Window',hanning(512),'OverlapLength',128,'FFTLength',512);
surf(t, f, abs(s), 'EdgeColor', 'none');view(0,90);
Plot in this case was as follows
It is clear that some normalization has been done on the values to make plot brighter.
I was wondering that what exact normalization has been done for the plot of stft?

Accepted Answer

jibrahim
jibrahim on 19 Apr 2022
Hi Muhammad,
I beleive the plot you get with STFT uses log, so 20*log10(abs(S)+eps) is plotted.

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