Sonogram Explorer
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Introduction

This application displays spectral information using a sonogram, or short-time Fourier Transform (STFT). You can explore the effects of different window shapes and sizes on the resolution of the STFT.

The tool

Simply load a soundfile from the menu to see its STFT. Change the colormap and dB scale to see different features. Zooming in the waveform time-display will also zoom the sonogram. The play button will play only the portion showing. The "Interpolate" box will smooth the STFT, but this will take a long time to complete for large sounds. The slider to the left of the sonogram will scale the frequency axis.

The 'Explore Data' allows one to travel the partials in the sonogram to get detailed information about its frequency and amplitude envelopes, and the time information. These can be used with the additive synthesis program to attempt to synthesize the sound. This works especially well with birdsong (see Additive Synthesis Forest). Click the "explore" button (perhaps twice if there is an error), and click on the sonogram to get information about the partial frequency, time, and amplitude. Once finished hit enter to have this information displayed to the MATLAB command window.

Things to investigate

1. What happens to the frequency resolution and time resolution as the analysis window size increases?
2. How can you tell the difference between speech and other types of sounds using the sonogram?

Further reading

Credits

Produced by Bob L. Sturm and Dr. Jerry Gibson
Release date: August 1, 2004
Copyright 2004 University of California, Santa Barbara