When reading a spectrogram, why is a power of 20 considered higher than 120

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fadams18
fadams18 2022-9-7
评论： fadams18 2022-9-7
Looking at the spectrogram below, it appears the higher power in the cyan color. but its power value is around 20.
why is this the case? does lower value mean big power?

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回答（1 个）

Walter Roberson
Walter Roberson 2022-9-7
Those are not 20 and 120: those are -20 and -120 .
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fadams18
fadams18 2022-9-7
I did a similar plot with a different signal. but my colorbar seems to be inverted. or u reckon its the right way?
[S, feqStft, timeStft] = MyStft(x,win,hop, nfft, fs);
magStft = abs(S);
imagesc(timeStft, feqStft, mag2db(magStft));
colorbar;
set(gca, 'YDir', 'normal');
title('Original Spectrogram of Signal ');
xlabel(['Time (0 - ', num2str(timeStft(end)), ' seconds)']);
ylabel(['Freq (0 - ', num2str(feqStft(end)), ' Hz)']);

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