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Media and communications

Sound recording

A CD and the laser beam reader A CD and the laser beam reader Sound recording and reproduction is the electrical storage and re-creation of sound waves. In a digital recording, sound signals picked up by a microphone are converted to a digital form by a process of digitization. The recording can then be stored in a variety of media, including CDs, DVDs and Blu-ray discs or on computers, portable media players and smartphones. A digital audio signal must be changed back to an electrical signal during playback before it is sent to loudspeakers or earphones. The signal causes a diaphragm inside each speaker to form sound waves.

Edison and his phonograph in 1878Edison and his phonograph in 1878

First recording machine

The US inventor Thomas Edison (1847–1931) adapted the parts of a long-distance telephone he had invented to produce the first recording machine, which he called the phonograph. The first recorded sound he made on it was heard in 1878, when Edison recited the nursery rhyme “Mary had a little lamb”.

An old advert for the phonographAn old advert for the phonographHis phonograph was like a telephone, only with the vibrating parts connected to a steel needle. As Edison spoke into a horn, the needle "wrote" the pattern of vibrations on a piece of tinfoil wrapped round a drum, which was turned at the same time. When the needle was returned to the beginning of its written message and the drum turned again, the pattern cut in the foil made it vibrate in the same way. The telephone parts also vibrated and the sound came back out of the drum.

Alexander Graham Bell's Volta Laboratory made improvements in the 1880s, replacing the foil-wrapped drum with a wax-coated cardboard cylinder, and a needle that moved from side to side across it.

A wind-up gramophone from the 1920sA wind-up gramophone from the 1920s

Gramophone records

The first recorded words belong to Frenchman Édouard-Léon Scott de Martinville (known as Leon Scott), made using his invention, the phonautograph. It funnelled sound waves through a horn with a stylus on the end, which traced lines on soot-covered paper fixed to a turning cylinder. His recording of the French folksong "Au Clair de la Lune" was made on 9th April 1860, but not played back until 2008.

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