Spectrograms Spectrograms Spectrum diagrams are useful for seeing the state of a complex wave during a very short period of time. But in speech, sounds are constantly changing.
Spectrograms are a convenient way to diagram the changes in a sound's spectrum over time.
In a spectrogram, the horizontal dimension represents time and the vertical dimension represents frequency. Each thin vertical slice of the spectrogram shows the spectrum during a short period of time, using darkness to stand for amplitude. Darker areas show those frequencies where the simple component waves have high amplitude. In these, the dark areas are smeared over a wider area. Spectrograms let us look at, for example, the changing formants in a diphthong.