I saw that in acoustics an estimated impulse response of a room can be transformed using STFT/wavelets to a spectrogram as an analysis tool. However, I did not understand how the spectrogram is interpreted (in contrast to the spectrum of the impulse response which gives us the frequency response for example).

Also, are there other cases in which the spectrogram of impulse responses is used, and what are the intrepretations in those cases?


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    $\begingroup$ Can you cite a reference where the spectrogram of the impulse response is shown $\endgroup$ – user28715 Jul 26 '17 at 13:02
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    $\begingroup$ I think using a spectrogram would only make sense when the system is time-varying. You could then plot the frequency response as it varies over time. $\endgroup$ – MBaz Jul 26 '17 at 13:19
  • $\begingroup$ I would ad that it directly give an information about the decay of different frequencies, which tells you about the resonant frequencies of the room and also the reverberation. You don't see this directly with a spectrum $\endgroup$ – Florent Jul 26 '17 at 22:57

I think you are thinking of waterfall plots and/or cumulative spectral decay plots. They are spectograms in the widest sense of the word since their windowing function tends to be exponential. They are popular for plotting the response of speaker systems as they show group delay for various frequencies a lot more, well, graphically than the impulse response itself or a magnitude/phase plot of the transfer function would. Resonators can be used for straightening out an otherwise wobbly (for whatever unrelated reason) frequency response magnitude at the cost of introducing delays.

The resulting lack of "impulse accuracy" which leads to problems with sound clarity and spatial perception is not easily apparent with other representations.

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