A spectrogram preserves timing of acoustic changes in a note

Evidence

In terms of the timbre of the note, it is not only the variations that occur during the onset and offset that are of interest but also how they change with time. Therefore an analysis method is required in which the timing of acoustic changes during a note is preserved in the result. One analysis technique commonly used for the acoustic analysis of speech is a plot of amplitude, frequency and time known as a “spectrogram.” Frequency is plotted on the vertical scale; time on the horizontal axis and amplitude is plotted as the darkness on a gray scale, or in some cases the color, of the spectrogram. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1433

Categorization

• DEFINE: Defines the spectrogram as a three-axis plot (frequency, time, amplitude-as-darkness) used to preserve onset/offset timing in speech analysis.