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The phonautograph is the earliest known device for recording sound. Previously, tracings had been obtained of the sound-producing vibratory motions of tuning forks and other objects by physical contact with them, but not of actual sound waves as they propagated through air or other media. Invented by Frenchman Édouard-Léon Scott de Martinville, it was patented on March 25, 1857. It transcribed sound waves as undulations or other deviations in a line traced on smoke-blackened paper or glass. Intended solely as a laboratory instrument for the study of acoustics, it could be used to visually study and measure the amplitude envelopes and waveforms of speech and other sounds, or to determine the frequency of a given musical pitch by comparison with a simultaneously recorded reference frequency. Apparently, it did not occur to anyone before the 1870s that the recordings, called phonautograms, contained enough information about the sound that they could, in theory, be used to recreate it. Because the phonautogram tracing was an insubstantial two-dimensional line, direct physical playback was impossible in any case. Several phonautograms recorded before 1861 were successfully played as sound in 2008 by optically scanning them and using a computer to process the scans into digital audio files. == Construction == Édouard-Léon Scott de Martinville, a printer and bookseller by trade, was inspired when he happened to read about the anatomy of the human ear in the course of his business. His phonautograph was constructed as an analog of the ear canal, eardrum and ossicles. Scott created several variations of the device. The functions of the ear canal and eardrum were simulated by a funnel-like horn or a small open-ended barrel with a flexible membrane of parchment or other suitable material stretched over the small end. A pig bristle or other very lightweight stylus was connected to the membrane, sometimes by an indirect linkage which roughly simulated the ossicles and served as an amplifying lever. The bristle traced a line through a thin coating of lampblack—finely divided carbon deposited by the flame of an oil or gas lamp—on a moving surface of paper or glass. The sound collected by the simulated ear and transmitted to the bristle caused the line to be modulated in accordance with the passing variations in air pressure, creating a graphic record of the sound waves. Martinville's first patent described a flat recording surface and a weight-driven clockwork motor, but the later and more familiar form of his invention, marketed by Rudolph Koenig in 1859, recorded on a sheet of lampblack-coated paper wrapped around a cylinder which was hand-cranked. The cylinder was carried on a coarsely threaded rod so that it progressed along its axis as it rotated, producing a helical tracing. The length of the recording that could be accommodated depended on the speed of rotation, which had to be rapid in order to resolve the individual waveforms of various sounds with good detail. If only longer-term dynamics such as the cadences of speech were being studied, the cylinder could be rotated much more slowly and a longer recording could be made. Some phonautographs included a tuning fork or other means of simultaneously recording a known reference frequency. Several other inventors subsequently produced modified versions of the phonautograph and recorded the sound-modulated line by the use of various implements and in various formats, either in attempts to improve on Scott's apparatus or to adapt it to specific applications. In at least one instance, a complete return to the device's conceptual origins was made by employing the preserved parts of an actual human ear. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「phonautograph」の詳細全文を読む スポンサード リンク
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