Spectrograms are a means of visualizing the energy and pitch of a particular sound. In the above example of a blue whale call, this spectrogram (upper image) plots time (horizontal axis) versus frequency (vertical axis), with warm colors representing high acoustic intensity. The first part of the call is a pulsive sound which varies little in frequency, and the second is a frequency-modulated moan, represented by the down-sweeping curve. Often, the spectrogram is accompanied by a time series plot of the sound(lower image), where time is plotted on the horizontal axis, and amplitude or “loudness” is on the vertical axis. |
