What is the relation between the s output and the plot made by the spectrogram function?

11 次查看（过去 30 天）

Jostein Holmgren 2016-7-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/296761-what-is-the-relation-between-the-s-output-and-the-plot-made-by-the-spectrogram-function

评论： Jostein Holmgren 2016-7-22

I'm making a spectrogram, and wish to extract the mean power (dB) in various frequency ranges (e.g. mean power between 8-14Hz at each time point). From what I understand, the output s is a matrix of complex numbers, the real part of which is magnitude squared. Taking the square root of that, then using the mag2db function to convert to dB results in a plot which looks right, however, the units are way off. The spectrogram yields units ranging from -70 to 10 dB, while my plot ranges from 25 to 50 dB.

I'd like the two plots to be directly comparable, so any insight into how Matlab computes the spectrogram from the values of s would be helpful. Alternatively, if anyone knows a way to extract the values in the spectrogram directly, that would also be good.