How phonautograph works?

A phonautograph is an early device invented in 1857 by Édouard-Léon Scott de Martinville that captures sound waves as visual representations. It consists of a diaphragm that vibrates in response to sound, causing a stylus attached to it to trace the vibrations onto a rotating cylinder or a flat surface coated with soot or blackened paper. The resulting patterns, known as phonautograms, are essentially sound waveforms, but the device does not reproduce sound; it only records it visually. The phonautograph laid the groundwork for future sound recording technologies, illustrating the concept of capturing audio in a physical form.