A spectrogram is a picture of how sound changes with time, similar to the "voiceprints" one sees on TV shows.
This real-time spectrogram covers the full 22 KHz audio bandwidth, the same as a compact disk (CD).
The output is a display in the form a waterfall plot that presents the frequency spectrum of the audio as it changes in time. The horizontal axis is frequency plotted in semi-log scale. Lower frequencies are to the left, higher frequencies are to the right.
A moving horizontal line is added just ahead of the most recent horizontal line of data so the user can identify the latest data.
The user may choose the signal intensity be plotted on a color or gray scale. Red represents a strong signal, blue a weak signal.
Semi-log or linear plots is user-selectable via the Options menu in the upper right.
The sensitivity control operates on a logarithmic scale in order to cover the huge dynamic range of ordinary sounds, from very soft, to very loud. So expect to see the sensitivity levels with jumps such as 1, 2, 3, 5, 10, 20, 50, 100, 200 et c.
This spectrogram collects 1024 samples at a sampling rate of 44,100 Hertz every 150 milliseconds. Each collection of 1024 samples corresponds to a single horizontal line in the display as shown in the screenshots.
Have fun looking at the “sound prints” of ordinary things. To learn more about frequency spectra see the one-page tutorial on our website, https://sites.google.com/a/andwaves.com/www/home/about-fourier-transforms
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