Noun
An instrument by means of which a sound can be made to produce a visible trace or record of itself. It consists essentially of a resonant vessel, usually of paraboloidal form, closed at one end by a flexible membrane. A stylus attached to some point of the membrane records the movements of the latter, as it vibrates, upon a moving cylinder or plate.
Source: Webster's dictionaryWhile working that summer in Brantford, Bell experimented with a " phonautograph ", a pen-like machine that could draw shapes of sound waves on smoked glass by tracing their vibrations. Source: Internet
In 2008, phonautograph recordings made by Scott were played back as sound by American audio historians, who used optical scanning and computer processing to convert the traced waveforms into digital audio files. Source: Internet
Recordings made with the phonautograph were intended to be visual representations of the sound and were not to be reproduced as sound until 2008. Source: Internet
Reproduction of the recorded sound was not possible with the original phonautograph. Source: Internet
Scott's phonautograph was intended purely for the visual study and analysis of the tracings. Source: Internet