Revolutions in sound recording
Revolutions in sound recording

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Revolutions in sound recording

2 Cylinders or plates?

2.1 Edison starts with cylinders

I had a little gramophone; I'd wind it round and round, and with a sharpish needle it made a cheerful sound.

Flanders, M. and Swann, D. (1977) ‘The Song of Reproduction’ from The Songs of Michael Flanders and Donald Swann, London, Elm Tree Books and St George's Press, p. 99

In 1877 the young American inventor Thomas Alva Edison finally completed development of an invention capable of capturing, recording and playing back sounds. Edison called it the phonograph, from the Greek meaning ‘sound-writer’, and it is pictured with the inventor in Figure 1.

Figure 1: Edison with his phonograph

As is often the case with truly great inventions, Edison was not the only inventor working independently on recording sounds. In April 1877 a sealed letter was deposited at the Académie des Sciences in Paris by an impoverished French poet and amateur scientist, Charles Cros. The contents described an apparatus that:

consists in obtaining traces of the movements to and fro of a vibrating membrane and in using this tracing to reproduce the same vibrations, with their intrinsic relations of duration and intensity, either by means of the same membrane or some other one equally adapted to produce the sounds which result from this series of movements.

Gelatt, R. (1977) The Fabulous Phonograph, London, Cassell & Company, p. 23

Unfortunately Cros could not afford to patent his idea and it was Edison who, in the late autumn of 1877, filed for a US patent on his phonograph. Differences existed between the two inventions as, for example, in Cros proposing a glass disc whilst Edison actually used a tin-foil cylinder.

Activity 4

Listen to the audio track below. It is a recording of Edison speaking the nursery rhyme ‘Mary Had a Little Lamb’ made in 1927, 50 years after he made the original recording in 1877. None of his original 1877 recordings have survived.

Click below (10 seconds)

Download this audio clip.Audio player: ta212_3_001s.mp3
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The sound quality in the clip of Edison speaking that you have just listened to is not very good in comparison to what we have come to expect today. This is because the system used an acoustic recording method, described in Box 1.

Box 1: Sounds on cylinders

Figure 2: The acoustic recording and playback process

Edison's method of recording and playback used an acoustic (or mechanical) process to record sounds onto tin-foil, as illustrated in Figure 2. A stylus, a small pointed stem of diamond or sapphire, was coupled to a diaphragm; these together comprised the soundbox. A conical horn, attached to the soundbox, amplified the sound vibrations. The sideways movement of the soundbox was controlled by a feed-screw that turned when the cylinder was rotated. To record a message, the cylinder was turned while you shouted into the horn. Sounds with sufficient energy caused the stylus to vibrate vertically and cut a groove with a profile that undulated in sympathy with the vibrations. On playback a stylus, again controlled by a feed-screw, followed the original track. The undulations in the groove picked up by the stylus set the diaphragm vibrating which, once magnified by the horn, recreated the sounds. Unfortunately tin-foil was so soft that replaying the message destroyed the undulations in the groove, so the sounds could be played back only once.

Activity 5

Run the Flash animation below. This animation demonstrates Edison's mechanical recording and playback process. It is based on his original design for the phonograph, which was patented in 1878.

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Activity 6

What does the fact that a person had to shout into the horn of the recording machine, as described in Box 1, tell you about the sensitivity of Edison's apparatus?

Answer

Comment

The fact a person had to shout indicates that the recording machine was very insensitive. This was due to the mechanical stiffness (inertia) of the mechanism that cut the groove into the recording medium, which in this case was tin-foil. This had a direct effect on the frequency response and dynamic range of mechanical recording machines.

An article in the Scientific American of 22 December 1877 described a visit by Edison to their New York office with his phonograph.

Mr. Thomas A. Edison recently came into this office, placed a little machine on our desk, turned a crank, and the machine inquired into our health, asked how we liked the phonograph, informed us that it was very well, and bid us a cordial good night. These remarks were not only perfectly audible to ourselves, but to a dozen or more persons gathered around …

By mid-1878 Edison had produced several versions of his phonograph, even experimenting with tin-foil discs, which he abandoned as he found the quality of reproduction deteriorated towards the centre. Although still far from perfect, the North American Review of June 1878 printed Edison's ten uses for his invention, which are summarised as follows:

  1. Letter writing and all kinds of dictation without the aid of a stenographer.

  2. Phonographic books which will speak to blind people without effort on their part.

  3. The teaching of elocution.

  4. Music – the phonograph will undoubtedly be liberally devoted to music.

  5. The family record – preserving the sayings, the voices and the last words of the dying members of the family, as of great men.

  6. Musical boxes, toys, etc. – a doll which may speak, sing, cry or laugh may be promised our children for the Christmas holidays ensuing.

  7. Clocks that should announce in speech the hour of the day, call you to luncheon and send your lover home at ten!

  8. Preservation of language by reproduction of our Washingtons, our Lincolns, our Gladstones.

  9. Educational purposes – such as preserving the instructions of a teacher so that the pupil can refer to them at any moment; or learn spelling lessons.

  10. The perfection or advancement of the telephone's art by the phonograph – making that instrument an auxiliary in the transmission of permanent records.

Activity 7

All the above ideas have been developed in one way or another. Which of the above do you consider have benefited the most from advances in digital audio technologies?

Answer

Comment

Although all the ideas have benefited in one way or another, the advances have been in different ways. Not all these ideas require the wide frequency response, high dynamic range and low signal-to-noise characteristics demanded from high-quality audio systems for music reproduction. The convenience of digital voice recorders for dictation and talking books, and the ability to use multimedia in general and particularly in language education, has used the advantages of digital audio compression techniques rather than striven for ultimate sound quality. This has been similarly exploited in telephone answering machines and voice storage systems where audio quality is not as important as storage capacity.

Perhaps surprisingly, a miniature phonograph was developed and installed inside a toy doll as mentioned in Item 6 above. Figure 3(a) is a photograph of such a phonograph beside the doll in which it was used. Surely this must be the forerunner of the talking greetings card, which contains a small circuit board and loudspeaker as shown in Figure 3(b).

Figure 3: (a) A miniature phonograph alongside a toy doll in which it was used; (b) the digital audio circuit board and loudspeaker from a modern talking greetings card

Strangely, Edison did not continue development of his phonograph at this time. Following a visit to view an eclipse of the sun in the state of Wyoming, USA, in 1878, he cast aside his work on recording sounds and devoted all his energies to the development of the electric lamp. (I wonder, was this due to the darkness created by the eclipse?)

TA212_3

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