[music-dsp] spectrograph / sonogram visualization

douglas irving repetto douglas at music.columbia.edu
Wed Jul 4 02:42:51 EDT 2001


Aaron Brick wrote:
> 
> hello all,
> 
> i'm new to the list, and finding it fun & educational. thanks for having me.
> 
> i have been experimenting with visualization techniques, and having gotten
> familiar with the conventional amplitude/time and fourier
> amplitude/frequency graphs, i'm trying to determine how to get a
> frequency/time graph; these are called spectrographs or sonograms?


hi aaron, 

i don't think there's much consensus on what the different graphs are
called. i've seen various names applied to various graphs. what i think
of as a sonogram is a three dimensional plot of a signal's spectra in
time. the x axis is usually time, the y axis is usually frequency and
the z axis (brightness of the image) is usually amplitude. so with a two
dimensional image you can represent all three dimensions.

here's an old application of mine that let you manipulate these
3-dimensional graphs in real time:

http://music.columbia.edu/~douglas/portfolio/squiggy.html


> there is a built-in function called "specgram" which i have not had success
> using;


in what program?

> since i want to understand the theory of such a transform i'm asking
> here. also, are there any other useful 2D visualizations?

there are lots of ways to represent sounds in n-dimensions. see matt
ingals' recent post about his stereo image visualization software for an
example.

douglas


-- 
                        douglas irving repetto 
                  http://music.columbia.edu/~douglas 
                  http://shoko.calarts.edu/musicdsp
               http://music.columbia.edu/cmc/dorkbotnyc

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