Some of the same people who worked on the Edison audio (Carl Haber) were also responsible for recovering the phonautograph audio. The phonautograph was essenti

Some of the same people who worked on the Edison audio (Carl Haber) were also responsible for recovering the phonautograph audio. The phonautograph was essentially a mechanical audio oscillograph. It graphed the sound waves on paper by conducting the acoustic vibrations to a stiff bristle up against lamp-black blackened paper wrapped around a slowly moving hand-cranked drum. The white traces left behind allowed properties such as frequency and amplitude to be estimated. I wonder if its inventor, Édouard-Léon Scott de Martinville, ever contemplated the problem of reproducing the graphed sound.