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Sound Recording and Reproduction

Before the digital age, analogue recording was the only option. Acoustic analogue recording is when a small microphone diagram that detects the changes in the atmospheric pressure, or acoustic sound waves. It is then recorded on phonograph, or a medium similar to it, in a representation of the sound waves. The reproduction of this sound is the reverse process. A bigger loudspeaker diaphragm is used to cause the changes to atmospheric pressure and forms sound waves. Analogue recording began in 1857, with a Parisian inventor Èdouard-Lèon Scott de Martinville. Èdouard-Lèon Scott de Martinville invented the phonautograph, which was a machine that could record sounds as they passed through the air, but couldn’t replay them. The phonautograph used a vibrating diaphragm and a stylus to trace sound waves on sheets of paper. The human voice was recorded for the first time by the phonautograph, the recordings were called “phonautograms”. Created in 1877 and patented in 1878, Thomas Edison invented the first practical sound recording and reproduction device, the mechanical phonograph visit:- cylinder. The mechanical phonograph cylinder engraved the recordings on the outside surface, then replays them on a mechanical cylinder phonograph. A type of Phonograph record is the Edison Diamond Disc Record, created by Thomas A. Edison Inc.. The record, made of tinfoil, was wrapped around a metal cylinder with grooves and a stylus that was sound vibrated indented the tinfoil as the cylinder was rotated.

The phonograph led to what we now call records. The earliest form of records was called the “Gramophone”. The Gramophone was invented by Emile Berliner in 1889, in the US. The master recordings were recorded on zinc plate disks, then electroplated, and then a negative-image was made from them and used to stamp discs. Initially, recordings were made through all acoustic means. The sound would be collected by a large horn, then piped into a diaphragm, which would then vibrate the cutting stylus. Despite the success with the acoustic recording, in the 1920’s, engineers at Western Electric and Orlando Marsh created a way to capture sound with a microphone. The sound would be captured with a microphone, rather than a horn, which would amplify it through vacuum tubes, creating an electric signal. The vacuum tubes, originally dubbed Audion triode vacuum tubes, created in 1906 by Lee De Forest, were an electronic valve that amplified weak electrical signals. Using the amplified electric signal from the vacuum tubes, an electromagnetic recording head would be driven. Western Electric pioneered the use of mechanical analogs of electrical circuits. They created the “rubber line” recorder for cutting the groove into the wax master in the disc recording system. This started the recording system that is still occasionally used today to record vinyl records. Now that sound had become easier to record, people started to experiment with using it for films. During the 1920s, early motion picture sound systems like Phonofilm used optical recording technology. Optical recording technology is where the audio signal is graphically recorded on photographic film. When playing these films, the film projector used a light and a photoelectric cell to convert the recorded variations back into electrical signals, which were then amplified. The audience heard these amplified electrical signals after the signals were sent to loudspeakers behind the screen.

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