APA Dictionary of Psychology

the procedure of analyzing a sound source (typically human speech) in terms of its variations in frequency and intensity over time. The visual record so produced is a sound spectrogram (often shortened to spectrogram), a quasi-three-dimensional representation of sound. The sound spectrum, measured over a relatively brief interval, is plotted by the sound spectrograph as a function of time on the x-axis while frequency is plotted on the y-axis and intensity is depicted by shading or color. A spectrogram provides an imperfect representation of the perceptually relevant aspects of sound.