spectrograph (n.)

An instrument used in ACOUSTIC PHONETICS which provides a visual representation of the acoustic features that constitute the sounds in an UTTERANCE. The original sound spectrograph produced a three-dimensional visual record, or spectrogram, of an utterance, in which time is displayed horizontally, frequency vertically, and intensity by the relative blackness of the marks, on a sheet of sensitized paper. Today, spectrographic information can be generated electronically and displayed on a screen.