"How are sounds viewed and analyzed?" (continued)
Another way scientists and musicians look at sound is with spectrogram. A spectrogram shows the frequencies present and at what times in the sound they are present. It gives the same information as an animated spectrum but in a static image. A spectrogram represents different sound energy levels with different colors. It is similar to a contour map or bathymetric map where the colors represent land height or water depth. Different computer programs and different people use different color schemes to represent the energy levels in spectrograms but they all convey the same meaning. On the DOSITS website, dark colors, blue and black, are low energy and light colors, yellow and white, are high energy.
The spectrogram below is of the Atlantic Croaker. Some spectrograms will be presented with the wave form above the spectrogram. Below the image are options to view movies in QuickTime format and Windows Media Player format. The movies show a white bar moving across the spectrogram as the sound is played. These movies help visualize the sound.
Atlantic Croaker Spectrogram:
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Choose a format to visualize the Atlantic Croaker:
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Notice that the energy is concentrated at higher frequencies in the first half and at lower frequencies in the second half of the spectrogram.
Spectrograms are often used to present the sounds made by marine mammals. Bird songs, and sounds from other land animals, are also regularly represented by spectrograms.
There are other ways of viewing sounds and other properties of sounds that scientists and musicians are interested in "seeing". On this web site, where "visualizations" of a sound are available, a spectrogram is used. Some sounds in the Audio Gallery have an animated spectrogram like the movies above. Spectrograms are also used to illustrate various features of different sounds in the Animals and Sound section of this web site.
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