Spectrograph

A sound analyser with graphic output showing the spectrum or frequency content of a sound and its variation in time. It is commonly used for speech analysis, and is sometimes called a sonagraph or visible speech. The graphic output is called a spectrogram or sonagram.

Compare: Level Recorder, Oscilloscope, Sonography, diagrams under Fourier Analysis.

Sound spectrograph (sonagraph). A sound of 2.4 sec duration is transferred to the magnetic disk and then repeatedly sampled as the disk rotates with the recording drum. The stylus passes a spark to the drum, etching the paper (from Winckel, Music, Sound and Sensation, Dover, 1967, p. 160, used by permission).

Spectrogram or sonagram of a two-second segment of speech, namely the phrase "I can see you." The dark areas show regions of strong intensity in the spectrum, such as formants and consonants.