RSS Feed for the unit Revolutions in sound recording

Introduction

This unit looks at the ways in which technology has influenced the music industry and how this has changed the way we listen to music and buy records. It is a brief history of the recording industry from its beginnings at the end of the nineteenth century. Step changes in technology will be highlighted in a story that often is as much about the people who built the industry and the recordings they made as about the technologies that were developed and used.

Please note that Activity 1 is optional and requires additional materials and software.

Learning Outcomes

By the end of this unit you should be able to:

explain correctly the meanings of the emboldened terms in the main text and use them correctly in context;
give a brief account of the history of the record industry;
describe the methods used for storing analogue audio recordings introduced in the main text, highlighting their technological aspects;
make informed judgements as to the quality of a sound recording through analysis of the audio signal.

1 Capturing sound

Have you ever listened carefully to a recording of your own voice?

In this first activity, I want you to make a short recording of your voice.

Activity 1 (Optional)

Note: This optional activity requires the use of a computer microphone and sound editor software, such as Audition or Audacity, which is free to download from audacity.sourceforge.net.

Using the equipment noted above, make a recording of yourself reciting the following well-known children's nursery rhyme:

Mary had a little lamb, Its fleece was white as snow.

And everywhere that Mary went The lamb was sure to go.

The reason for this choice of rhyme will become clear in a moment. Play the recording back to yourself. How do you sound? Do you think your voice sounds like you?

Now read the answer

Comment

Well, do you think your voice sounded like you? Probably not – due to the directivity of the voice, you do not hear it as others do and so it sounds unrealistic to you in a sound recording. However, because you know that the technology you are using is capable of accurately reproducing sounds I hope you have confidence that what you are hearing accurately represents how you sound to others.

The first sound recording of a human voice, actually reciting the nursery rhyme ‘Mary Had a Little Lamb’, was made over 125 years ago. Just imagine back then the reaction of people the first time they heard the sound of a human voice coming from a machine – especially if it was theirs!

The phonograph [recording machine] was remarkable partly because it did not look human – it spoke just like a person, but it looked like a machine, a simple cylinder of tinfoil.

Wood, G.,2002, Living Dolls, London, Faber and Faber, p. 121

So great was this invention and so insatiable was (and still is) our need to hear recorded sounds – especially music – that within 25 years sound recording had become a global industry.

Before sound recording was possible, few people had the opportunity to hear music in the way we take for granted today. Apart from expensive musical boxes and mechanical music players, the only way music could be heard was in live performances. Take a moment to think how your life would be without being able to listen to music from CDs, records, tapes, radio, television or even the web. How often would you listen to music if you could hear it only by attending live performances or making it yourself? The following activity asks you to think about listening to music before sound recording was invented.

Activity 2

Think of how people listened to music before the advent of sound recording. Try to put yourself in their place and make a list of the various ways in which you might hear music. Is there a common thread that you can discover about the experience?

Now read the answer

Comment

I thought of the following:

places of religious worship (singing hymns, listening to the organ, etc.);
at school (nursery rhymes, group songs and dance);
in the home (barrel organ, musical box or player piano);
live concerts (listening to the band in a local park, going to the music hall, a classical concert or a musical theatre performance);
dancing (to music from local bands).

A common thread that occurs to me is that on many occasions music was created by people (amateurs rather than professionals) meeting together – at church, school or the local public house for example. Most of the music was live, with just the possibility of hearing a mechanical instrument such as a barrel organ.

Another very significant factor is that, as you have just seen in Activity 1, recordings have allowed performers to hear what they sound like to other people. In his book, Robert Philip says:

Musicians who first heard their own recordings in the early years of the twentieth century were often taken aback by what they heard, suddenly being made aware of inaccuracies and mannerisms they had not suspected.

Philip, R. (2004) Performing Music in the Age of Recording, Yale University Press, p. 25

He goes on to argue that the effect of recording has been to change many features of general performing style. Before recording was possible, when a single performance of a work might be the only chance many listeners would have to hear that particular work, performers tended to play in a way that would now seem exaggerated and mannered, such was their determination to underline the music's expressivity and its major structural features. This style of performing survived into the twentieth century, and can be heard in many early gramophone recordings. However, the spread of recordings, and the opportunity they afford for the listener to become familiar with a large body of repertoire works, has fostered a performing style that is less concerned with pointing up salient details of the work (which many listeners now know from recordings) than with eliminating mannerisms and imperfections from the performance. Philip argues that in the age of recording, performers have become especially concerned with precision and accuracy, whereas performers (and listeners) of the past placed less value on these qualities.

You may already know that sounds from any source are conveyed to our ears by small variations in air pressure. These variations, which are captured by the eardrum, cause impulses to be sent to the brain, allowing us to make sense of the sound. We cannot store the sound but our memory allows us to recognise it if it reoccurs. A microphone also contains a membrane, called a diaphragm, that responds to the variations in air pressure by generating tiny electrical impulses, which may be amplified and recorded (or stored) by a suitable medium. Playing back the recording, again by using a diaphragm but this time a cone in a loudspeaker, regenerates these variations in air pressure with sufficient energy so as to act on the eardrum in the same way as the original sound. This makes the recognition of the sound possible, as if it came from the original source. In order for us to believe we are listening to the original sound, the recording and playback systems must not distort the original signal in any way. The next activity revises the three main parameters that determine audio system quality, and these will be used throughout this unit as a means of comparing the quality of the various different audio systems that are discussed.

Activity 3

Bandwidth, dynamic range and signal-to-noise ratio are three parameters that can be used as a measure of the quality of an audio system. What do you understand by each of these terms, and what is considered a rough acceptable value of each of them for a good-quality audio system designed to play CDs?

Now read the answer

The bandwidth of a system is the range of frequencies over which an audio device responds equally (i.e. has a flat response). In the case of an audio CD system the frequency response would need to be flat over the range of frequencies the CD contains, i.e. 20 Hz to 20 kHz.

Dynamic range is derived from the amplitude range between the loudest level that can be reproduced without producing distortion and the softest level that can be reproduced without being enveloped in noise. Dynamic range is the ratio between these two values and is usually expressed in decibels. In the case of an audio CD system the dynamic range needs to be at least 90 dB.

Signal-to-noise ratio gives an indication of the noise in the system. It is expressed as a ratio of the wanted signal power to the noise power in the system, and is usually expressed in decibels. A typical value for digital audio equipment is 100 dB.

As you will discover, the technologies used within the record industry have not always been capable of delivering sounds from systems with ideal characteristics for recording and playback. In fact, user convenience can be as important a consideration as the fidelity of the reproduced sound.

2.1 Edison starts with cylinders

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)

Listen in separate player Click play to start.

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 linked 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. Please note: to view this animation correctly, you will need to click on the ‘Launch in separate player’ link below.

Launch in separate player

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?

Now read the 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:

Letter writing and all kinds of dictation without the aid of a stenographer.
Phonographic books which will speak to blind people without effort on their part.
The teaching of elocution.
Music – the phonograph will undoubtedly be liberally devoted to music.
The family record – preserving the sayings, the voices and the last words of the dying members of the family, as of great men.
Musical boxes, toys, etc. – a doll which may speak, sing, cry or laugh may be promised our children for the Christmas holidays ensuing.
Clocks that should announce in speech the hour of the day, call you to luncheon and send your lover home at ten!
Preservation of language by reproduction of our Washingtons, our Lincolns, our Gladstones.
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.
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?

Now read the 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?)

2.2 Bell and Tainter improve the phonograph

2 Cylinders or plates?

2.2 Bell and Tainter improve the phonograph

If Edison was not willing to continue development of the phonograph then others were. Alexander Graham Bell, who had risen to prominence through his invention of the telephone, took a great interest in recording sounds, even suggesting to Edison that they might collaborate. Edison refused, so Bell set about developing a recording machine with the assistance of his cousin Chichester Bell, a chemical engineer, and Charles Tainter, a scientist and instrument maker. By 1887 Bell and Tainter had succeeded in producing a recording machine that they called the graphophone (meaning ‘sound-pencil’). The graphophone was largely similar to the phonograph, but in place of tin-foil they used cylinders of hard wax coated onto cardboard sleeves as the recording medium. This was a great technical advance, for it not only gave much greater quality of reproduction but also allowed the recording to be replayed many times. Unfortunately, the low sound level when it was played back necessitated the use of ear tubes, as illustrated in Figure 4.

Figure 4: A graphophone being used for dictation by a nineteenth-century ‘audio typist’

Activity 8

Given the fact that wax was easier to cut than tin-foil, why do you think wax cylinders offered an improved sound quality?

Now read the answer

Comment

The sound quality was improved because there was less stiffness (inertia) in the recording system. This gave greater sensitivity as well as an improved frequency response and a raised signal-to-noise ratio. These improvements were only marginal compared with today's technologies but nevertheless were a distinct advance.

With his work on the electric lamp successfully completed, Edison returned to what he always called his favourite invention, insisting that the phonograph had never been far from his thoughts. What actually came out of his laboratory, which he called his ‘Perfected Phonograph’, looked remarkably similar to the graphophone. However, Edison used a solid wax cylinder rather than a wax-coated cardboard sleeve. This worthwhile improvement allowed the surface of the cylinder to be shaved, so erasing the original recording to allow the cylinder to be used again. Bell and Tainter quickly adopted solid wax for their graphophone. The litigious business society sat back, rubbed their hands, and waited for a bitter fight between the two companies over the patent rights!

However, the expected lawsuits did not arise. Firstly, the wording of the two patents was different. Edison described his recording technique as ‘embossing or indenting’ the medium, whereas the Bell-Tainter patent portrayed their way of recording as ‘engraving’, implying a different approach. Secondly, a businessman named Jesse H. Lippincott, who was looking to invest cash in a new venture, offered to invest in both inventions, thus securing sole rights to sell recording machines through his North American Phonograph Company.

The whole enterprise nearly failed for, just like Edison and Bell, Lippincott saw the future of the recording machine for dictation in businesses such as government bureaux and offices. Actually shorthand typists did not appreciate this use of the machine, seeing it as a threat to their jobs. They even went as far as sabotaging the machines, making them useless for dictation. After two years of unsuccessful trading Lippincott, now in ill health and with poor finances, lost control of his company to Edison, who still saw only business potentials for his invention:

He could not or would not countenance the potentialities of the phonograph as a medium for entertainment.

Gelatt, R. (1977) The Fabulous Phonograph, London, Cassell & Company, p. 44

Fortunately for Edison the Columbia Phonograph Company, one of his subsidiaries, recorded popular songs of the day on cylinders. They could be played back using specially adapted ‘coin-in-the-slot’ phonographs, which were situated in public places such as drugstores and saloons. Popular songs could be heard ‘for a nickel a time’, as illustrated in Figure 5. Their popularity demonstrated a public demand for recorded music.

Figure 5: Entertainment in 1891, ‘for a nickel a time’

Edison was finally convinced of the phonograph's possibilities for musical reproduction, but as ever he wanted to do it his own way, and his first move was to liquidate his existing phonograph companies. This opened the way for a coalition between two rivals, Bell and Tainter's American Graphophone Company and the now independent Columbia Phonograph Co. Working together they were soon able to offer a clockwork-powered graphophone for $50 with a catalogue of over a thousand pre-recorded cylinders. By Christmas 1897 they were selling a $10 clockwork-powered graphophone that could, as the ads said, ‘reproduce music as loudly and brilliantly as the highest price machine’ (Gelatt, 1977, p. 70). One similar to the original graphophone is illustrated in Figure 6.

Figure 6: A clockwork cylinder player

To compete, Edison offered his clockwork-powered ‘Home Phonograph’ for $20 (see Figure 7) which, apart from minor modifications, sold for over 30 years.

Figure 7: The Edison Home Phonograph

The Royal Scottish Museum, Edinburgh

2.3 Berliner experiments with plates

2 Cylinders or plates?

2.3 Berliner experiments with plates

Emile Berliner was a young German immigrant to the USA with an interest in science. Whilst working in several menial jobs he educated himself in basic physics and chemistry, eventually building a small laboratory at his boarding house. Experiments with electricity and acoustics led to his invention of a new telephone transmitter, which he sold, enabling him to set up as a full-time inventor. He became interested in recording sound through studying a device called the phonoautograph. This apparatus inscribed sound vibrations as a lateral trace onto lamp-blacked paper using a diaphragm and stylus. Berliner thought that this lateral motion could offer superior recording quality to Edison's vertical method (see Section 2.4). He also decided to use a disc, which he called a plate, rather than a cylinder as the recording medium. The plate was placed onto a turntable over a central spindle that fitted into a hole in the middle of the plate. The turntable was then rotated at a fixed speed. This overall design was sufficiently different from the phonograph to allow it to be patented in 1887 using the name gramophone.

Note: In the USA, phonograph is the generic name given to all record-playing equipment. In the UK gramophone is more generally used, although phonograph may be used when referring to cylinder players.

Berliner made his plates from a tough rubber-based compound called vulcanite, allowing the groove to be sufficiently deep to ensure the soundbox was guided by the groove, eliminating the need for the phonograph's complex feed-screw mechanism. The deep groove also allowed cheap, replaceable steel needles to be used in place of the delicate jewel stylus found in the cylinder machines. This made the gramophone, illustrated in Figure 8, cheaper to manufacture than the competition. In 1894 Berliner's United States Gramophone Company released their first single-sided (which means the sound was recorded on just one side) 7-inch (18-cm) diameter disc.

Figure 8: The Berliner ‘Seven Inch’ hand-cranked gramophone

The Royal Scottish Museum, Edinburgh

An important point to note is that unlike its rivals, the gramophone had no means of recording sounds – it was designed from the outset only to play back pre-recorded sounds. This demonstrated a high degree of faith by Berliner that people would be happy just to listen to sounds (and music in particular) in their own homes.

2.4 Cutting the groove

2 Cylinders or plates?

2.4 Cutting the groove

The vertical (up-and-down) cutting method, which was nicknamed ‘hill-and-dale’, shown in Figure 9(a) was invented by Edison. The lateral (side-to-side) motion developed by Berliner is shown in Figure 9(b). In both cases the undulations in the groove are directly analogous to the sound vibrations.

Figure 9: Stylus motion in a recording: (a) vertical; (b) lateral

The phonograph pickup was positioned by a feed-screw so if the groove disappeared, as it sometimes did, the position of the pickup was not affected. On the other hand, the gramophone pickup was simply guided by the groove, which in consequence had to be much deeper to avoid the pickup skating across the disc's surface. Figure 10 compares an actual vertical-cut phonograph cylinder in (a) with an old lateral-cut 78 shellac disc in (b) and a vinyl LP disc in (c).

Note the difference between the vertical and horizontal undulations and also the depth of the groove in (a) and (b).

Figure 10: The grooves on (a) an Edison cylinder, (b) a 78 rpm shellac disc and (c) a vinyl LP disc

When cutting the groove in the recording medium, the level of the captured sound directly affects the deflection of the cutter. A loud sound results in a large deflection causing a deep cut using vertical recording or a wide horizontal deflection for lateral recording. When recording on discs, the engineer had to ensure that loud passages did not cause the lateral cutter to make such a wide deflection that it broke through the groove wall of an earlier part of the recording. The groove spacing would be set sufficiently wide to ensure that this would not happen. However, this caused other problems because the wider spacing reduced the recording time. In the early days of disc recording, singers might be asked to turn their heads away from the horn or microphone during loud passages to ensure their voices kept the cutting stylus displacement to a reasonable level. This could be thought of as a very crude example of audio compression.

Cylinders had a standard groove pitch of either 100 or 200 tracks to the inch (40 or 80 per cm) depending on the playing time.

Because lateral-cut groove spacing depends upon the amplitude of the sounds to be recorded, as explained above, the spacing had to be individually set for each disc; but on average it was 70 tracks per inch (30 per cm).

Later record cutters offered automatic dynamically variable spacing (the groove spacing was varied within a disc as the sound got louder or softer). This allowed a closer groove pitch for quiet sounds whilst avoiding the likelihood of a loud sound breaking the wall of the groove, and therefore maximised the playing time. This can be seen in the spacing of the grooves of the LP shown in Figure 10 (c).

As the recording medium (i.e. the cylinder or disc) is turned a linear groove is cut. The maximum linear speed (surface speed) of the medium relative to the stationary cutting head determines the highest frequency that can be recorded without distortion. The cutter makes a wave with a length that is a function of the linear speed and sound frequency. The linear speed of a cylinder remains constant at 44 cm/s. However, because a groove around the outside of a disc is much longer than a groove towards its centre, the linear speed varies over the surface of a 78 rpm disc from 120 cm/s at the edge down to 44 cm/s at the middle (remember that the rotational speed is constant). The corresponding wavelength of a 1 kHz sine wave recorded on a 78 rpm disc thus varies from 1.2 mm down to 0.44 mm. The diameter of the pickup stylus or needle also determines the upper frequency response. This is because a blunt needle will not sit right at the bottom of the V-shaped disc groove, and will therefore not follow very high-frequency ‘wiggles’ in the groove, whereas a sharper needle will fit right into the bottom of the groove and so will be able to follow the fast lateral groove movements much better.

Activity 9

(a) From reading this section, what restrictions do you consider to have been placed on the ultimate sound quality of cylinder and disc recordings in terms of bandwidth and dynamic range?

(b) Why were these restrictions employed?

Now read the answer

Comment

(a) The linear speed controls the upper bandwidth frequency. If the cylinder or record would have revolved faster, the linear speed would have increased and with it the upper frequency response. In the case of discs the track spacing is dependent on the dynamic range, as louder sounds require a greater deviation of the groove meaning an increased track spacing.

(b) In both cases the recording time (capacity) of the recording medium would be decreased, shortening the playing time. A trade-off between ultimate quality and sound quality had to be made.

Activity 10

Listen to the two audio tracks below. The first track contains an original recording by Emile Berliner and this is followed in the second track by a repeat of the recording of Edison speaking the nursery rhyme ‘Mary Had a Little Lamb’, made in 1927. How do you think Berliner's recording compares with that of Edison? Can you think why both men should have chosen to recite nursery rhymes?

Click below (17 seconds)

Listen in separate player Click play to start.

Click below (10 seconds)

Listen in separate player Click play to start.

Now read the answer

Comment

The recording by Berliner was taken from an original 5-inch (13-cm) diameter vulcanite disc made in 1889. I think you will agree that the reproduction is poor compared with the recording of Edison. However, remember that Edison's recording was made in 1927 as a demonstration of his original invention. I wonder why both Edison and Berliner recited nursery rhymes? Perhaps neither could think of anything more propitious to say at the time, but bearing in mind the poor quality of the sound, it may have been that using well-known rhymes would make the recording more comprehensible. Maybe it was an early marketing ploy.

Activity 11

(a) Which cutting method, vertical or lateral, would give the recording engineer the opportunity to record the louder sound?

(b) Why was it advantageous to record sounds at the highest possible level in these early recordings?

Now read the answer

(a) Edison's vertical (hill and dale) method used on phonograph cylinders was more suitable for recording loud sounds, as a greater depth of deflection of the diaphragm was possible. Berliner's lateral groove on the gramophone disc limited deflection of the diaphragm, otherwise the groove wall would be broken. So, in principle, vertical recording gave a better dynamic range.

(b) The larger the movement of the diaphragm in the phonograph pickup the louder the sound, and so the signal-to-noise ratio was increased thus making the system more suitable for mechanical reproduction.

2.5 Making multiple copies

2 Cylinders or plates?

2.5 Making multiple copies

Berliner was aware that Edison had problems duplicating cylinders. Initially copies were made from a master cylinder using a mechanical engraving process. Unfortunately this method caused the master cylinder to wear out after making just a few copies, so performers had to be asked to record several masters to ensure enough cylinders could be duplicated. An improved recording system allowed multiple master cylinders to be made by feeding several recording phonographs from one horn, but the cylinder-copying process was still far from satisfactory.

It took Berliner six years to perfect disc duplication but it was time well spent, for the principles are still used today to manufacture compact discs. Box 2 compares the manufacturing processes for cylinders and discs.

Box 2: Cylinder and disc manufacture

A process to mass-produce cylinders was finally developed in 1901. Cylinders were moulded using a hard black wax medium that reduced playback wear. The process was known as ‘gold-moulded’ because a gold-coloured vapour was given off during the process. Sub-master moulds were created from the master cylinder, and the wax cylinders manufactured from these moulds. This meant that the artist had to record only a single master cylinder. About 150 cylinders a day could be produced from a single mould.

Disc manufacture using the Berliner process started with the creation of a master disc, known as a matrix. This was a wax-coated metal disc into which the artist cut the recording. Each master disc was inscribed with an identification number, known as the matrix number, which appears near the centre of every record near the label. The master matrix was then used to make moulding tools, known as matrix stampers, using an electroplating process that deposited a layer of metal onto the master. When separated from the master the stamper became a negative replica of the master. The stamper was fitted into a hydraulic press, along with an identification label and the disc material. Once perfected, up to three discs per second (180 per minute) could be pressed in this fully automated process. Early discs were stamped on just one side but eventually double-sided discs were developed that played on both sides.

Unfortunately Berliner's discs, one of which is illustrated in Figure 11, were of variable quality, tending to have flat spots in the groove that caused the pickup to skate across the disc surface (remember, the groove positioned the pickup). From 1897 a hard-wearing compound of shellac, slate powder and carbon black was used (shellac is a resin derived from the secretion of the Lac beetle, Coccus lacca, found in Malaysia). This improved the quality and lowered production costs. The abrasive nature of the slate dust sharpened the playing needle to ensure a continued good fit in the groove (so maintaining the high frequency response) but at the expense of users regularly having to replace worn-down needles – another source of income to record manufacturers! Shellac discs gave an acceptable surface noise and were easily mouldable at relatively low temperatures. At room temperatures shellac discs were brittle and shattered if dropped. Eventually, a relatively unbreakable plastic material called vinyl (short for polyvinyl chloride) was used to manufacture discs.

Figure 11: An example of Berliner's vulcanite disc

Activity 12

When a recording company makes a decision to issue a CD of a recording originally released on a 78 rpm disc, the remastering engineer prefers to get hold of the matrix and make the transfer from that rather than from a normal copy of the released disc. Why should this be the case?

Now read the answer

Comment

Every time an analogue recording is copied there is additional noise added to the original sound, lowering the signal-to-noise ratio. Using the original matrix will ensure the best possible sound. Unfortunately access to the original matrix is not always possible and many reissues of original 78 recordings use normal mass-produced discs.

2.6 Turning the handle

2 Cylinders or plates?

2.6 Turning the handle

The owners of the original hand-cranked gramophones were instructed that the standard velocity for ‘seven-inch plates’ was about 70 revolutions per minute. The owner was also warned that failure to turn the plate at the correct speed would lead to a lowering of the pitch if turned too slow, or a raising of the pitch if turned too fast. It is doubtful if true reproduction of the recorded sound was ever achieved by the owners of these machines! A better power source was needed and as electric motors were far too costly, a suitably powerful and inexpensive clockwork motor was used. It was designed and built by Eldridge Johnson, a craftsman with a passion for the gramophone who would later form Victor Talking Machines and Victor Records, which would become RCA-Victor. The clockwork motor proved an immediate success, with Christmas 1896 seeing the Berliner Gramophone Company of Washington, DC ahead of all the competition, with the factory being unable to keep up with the demand. By mid-1897 the ‘Improved Gramophone’, with a new Johnson-designed motor and soundbox, was launched. This model was destined to become one of the most familiar icons in the recorded music field for it was immortalised, along with a small black-and-white fox terrier dog called Nipper, in a painting by Francis Barraud, shown in Figure 12. This painting was to become the trademark of the HMV (His Master's Voice) Company in Europe and Victor Records in the USA.

Figure 12: Barraud with his painting of Nipper entitled ‘His Master's Voice’

The recording and playback speed would ultimately be standardised at 78 revolutions per minute (rpm), as explained below in Box 3. Actually this can never be taken for granted, because recording speeds varied from under 70 to over 80 rpm. To cater for these differences a speed controller was fitted to most gramophones.

Disc diameters also varied but 7-inch (18-cm) playing for two minutes, 10-inch (25-cm) playing for three minutes, and eventually 12-inch (30-cm) playing for up to five minutes became standard. Eventually recordings were put on both sides of the disc – known then, as now, as the A and B sides – offering better value and greater convenience to users.

Box 3: Why 78 rpm was chosen

Discs revolving at 100 rpm would have given a better sound through improved bandwidth but would have shortened the playing time of the disc to less than Edison's original two-minute cylinder. 40 rpm could have increased the playing time but would have offered a poor sound quality compared with cylinders. 70 to 80 rpm was a compromise offering a reasonable sound and an acceptable playing time. With the introduction of mains-powered synchronous electric motors a speed of 78 rpm became standard. This is because for these types of motor, the rotational speed is dependent on the mains supply frequency. With 78 rpm, simple reduction gearing could be used between the motor and the turntable that required minimal changes when converted from the European 50 Hz to the North American 60 Hz mains frequency supply or vice versa.

2.7 Music matters

2 Cylinders or plates?

2.7 Music matters

There was little difference in sound quality between the phonograph cylinder and the gramophone disc. The limited frequency response of the acoustic recording and playback process restricted the sounds that could be reproduced. Instruments tended to be limited to brass and piano, and middle-register voices (alto and tenor) were the most suitable. So why did the disc succeed over the cylinder? The answer has little to do with technology and much more to do with the tenor Enrico Caruso and the entrepreneurship of one man, as you can read in Box 4.

Box 4: Recording Caruso

On 18 March 1902 Fred Gaisberg, a senior representative of The Gramophone Company and the ‘father’ of recorded sound, set up an improvised recording studio in a bedroom at the Hotel di Milano in Milan, Italy. The studio was little more than a piano on packing cases and a gramophone recorder. In the afternoon ten arias were recorded by a young and relatively unknown Italian tenor, Enrico Caruso. His agent demanded £100 for the recordings, which the entrepreneur Gaisberg paid out of his own pocket. The Gramophone Company had refused to pay, sending Gaisberg the following reply to his cable requesting permission to record Caruso: ‘FEE EXORBITANT FORBID YOU TO RECORD’ (Northrop Moore, J. (1999) Sound Revolutions, London, Sanctuary Publishing, p. 92).

It is generally agreed that these were the first completely satisfactory recordings to be made. They were sold on premium 10-inch-diameter ‘Red Label’ discs at ten shillings (50p) each. They were an immediate success. Caruso's voice had an ideal quality for the recording technology of the time and he is considered to be the first serious musician to appreciate the value of recordings.

His later record of ‘Vesti la giubba’ from Leoncavallo's I Pagliacci, made in November 1902, sold over a million copies. Figure 13 shows a self caricature of Caruso – note The Gramophone Company's logo on the wall!

Figure 13: Recording Enrico Caruso – a self caricature

Ampex GB Limited

Other singers were encouraged to record for The Gramophone Company including, in early 1903, the tenor Francesco Tamagno, for whom Verdi had created the operatic role of Otello. Tamagno insisted that his 12-inch (30-cm) records sold for £1 each and had a special ‘Tamagno Label’, and he received a 10 per cent royalty on each record sold (Tamagno was the first artist to receive royalty payments for recordings). This was followed a year later by two famous female singers, Nellie Melba and Adelina Patti, who both insisted on their own labels, mauve and pink respectively, and a premium selling price of one guinea (£1.05). (At this time 30 to 35 shillings (£1.50 to £1.75) was a good weekly wage for a skilled craftsman.)

Activity 13

Listen to the audio track below. It is a recording of Enrico Caruso (1873–1921) singing ‘Questa o quella’ from the opera Rigoletto by Verdi (1813–1901). This was the second of ten recordings made by Fred Gaisberg in March 1902. You may notice that Caruso clears his throat at the end of the first verse – no editing facilities were available in 1902! This recording has been restored by Ward Marston..

Click below (2 minutes 17 seconds)

Listen in separate player Click play to start.

The reason why the records produced from the Caruso recordings were so popular was that he was singing popular music of the time and the quality of his voice suited the technology – a trained tenor uses a singer's formant to emphasise voice partials between 1 and 3 kHz, which centres on the frequency response of a mechanical gramophone.

Edison had little to offer in the way of competition to Berliner's evergrowing catalogue. He failed to make inroads into Europe and hence record the popular artists of the time, who tended to live and perform in that part of the world. Although the United States saw the origins of the talking machine, Europe really transformed it into a musical instrument by the choice of music and performers. Finally, in 1913, Edison introduced a disc, shown together with some of his cylinders in Figure 14. Typically, it had the same vertical-cut groove method used on his cylinders, which made it unusually thick (6.5 mm), and of course it needed a special Edison disc player. Despite offering a superior sound Edison's disc was too late – Berliner's gramophone records were too well established by virtue of the material they offered. The Edison Company continued to supply cylinders and discs until 1929, when manufacture finally ceased.

Figure 14: Examples of Edison's cylinders and discs

Activity 14

Suggest some reasons why the acoustic recording process limited the types of instruments and voices used.

Now read the answer

The frequency range of many instruments was outside that of the mechanical transducer. Timpani and large stringed instruments just would not be heard. Similarly, many of the small woodwind family suffered in this way. Further, the acoustic qualities of many instruments were too delicate to be reproduced above the surface noise of the disc. An alto or tenor voice with either a piano or brass instruments offered the best opportunity to obtain a good recording.

2.8 Good times and bad

2 Cylinders or plates?

2.8 Good times and bad

The music industry, like any other large industrial business, had good times and bad times. By 1924 the burgeoning of radio broadcasting in the United States caused a severe downturn in record and equipment sales, leading to amalgamations and bankruptcies of many of the record companies. Actually, radio broadcast studio technology proved of great importance to the record industry. The sensitive microphones and electronic amplifiers used in broadcast studios offered improved characteristics that were exploited in the record industry through the development of an electromagnetic cutting head by the American company Western Electric. Unfortunately, they agreed to sell electric recording technology (as it was known) only to American record companies. Not to be outdone, the far-sighted managing director of the British Columbia Record Company went to America and bought the then-ailing ‘States-Side’ company of the same name along with an agreement to use the new recording equipment, thereby securing the technology for use in Europe. To capitalise on the new technology, players with electromagnetic pickups, using an opposite technology to the cutter, were developed. Electric players rapidly replaced acoustic machines, as they were able to exploit the improved characteristics of the electric recordings. In particular, the new recordings were able to use electronic filtering or equalisation to improve the replayed sound quality, as described in Box 5.

Box 5: Electromagnetic pickups and equalisation

Audio signals are recorded as a lateral displacement or ‘wiggle’ in a linear spiral groove cut into the disc, as described earlier. A sinusoidal wave in the groove, as shown in Figure 15(a), will cause a voltage to be generated in the electromagnetic pickup coil, illustrated in Figure 15(b), due to the lateral motion of the stylus following the wiggles in the groove. (The stylus in the pickup moves very freely compared with the arm that is supporting it.)

Figure 15: (a) Sinusoidal signal in groove; (b) magnetic pickup

The level of the generated voltage is proportional to the frequency recorded in the groove, so as the frequency rises the output level rises. The maximum recorded level (the maximum amplitude of the groove ‘wiggle’) is fixed firstly by the groove spacing (if it is too high the groove wall breaks) and secondly by the ability of the stylus to follow the lateral movement in the groove (too large a ‘wiggle’ at too high a frequency and the stylus will be unable to follow the groove). The minimum recorded level is set by the noise in the system (mainly the noise generated from roughness in the disc material). To ensure that the amplitude of the groove ‘wiggle’ is reasonably constant over all audio frequencies, the lower frequencies (below 500 Hz) are reduced and the higher frequencies (above 2 kHz) are boosted when the groove is cut. This means that when the record is played back the opposite characteristics must be applied, i.e. the lower frequencies output from the pickup must be boosted and the higher frequencies reduced. In the late 1950s an international agreement was reached for the frequency characteristics of recording discs based on a specification from the Recording Industry Association of America (RIAA).

The ideal characteristic for such an RIAA replay amplifier is shown in Figure 16. The gain for frequencies above the low corner frequency is reduced until the middle corner frequency is reached. The gain then remains level until the high corner frequency is reached, when the gain is further reduced. Since it is not possible in practice to produce a response that has straight lines and sharp corners, Figure 16 also shows the actual response of a practical amplifier alongside this ideal response. This filtering should therefore restore or equalise the levels of the audio frequencies to those of the original performance.

Figure 16: Response of an RIAA replay amplifer

Prior to the RIAA agreement manufacturers specified their own equalisation, examples of which are included, along with the RIAA characteristics, in Table 1. The use of the RIAA characteristic also produces a useful improvement in signal-to-noise ratio. By attenuating the higher frequencies, ‘surface noise’ in the pickup output caused by dust and groove wear is reduced. However, boosting the lower frequencies means mechanical noise from the turntable and external electrical noise (e.g. mains hum) can be increased.

Table 1: Equalisation characteristics required for 78 rpm and LP disc media

Recording system	Low corner frequency	Middle corner frequency	High corner frequency	Level at 50 Hz*	Level at 10 kHz*
HMV 78	50 Hz	250 Hz	n/s^†	+12 dB	n/s^†
Columbia 78	n/s^†	300 Hz	1.6 kHz	+14 dB	−16 dB
RIAA LP	50 Hz	500 Hz	2.12 kHz	+17 dB	-13.6 dB

* These figures are relative to the amplifier gain at a frequency of 1 kHz.

† These figures are not specified.

Activity 15

Activity 3 should have reminded you that the frequency characteristics of an audio system should be substantially flat for frequencies between 20 Hz and 20 kHz. If a disc was replayed through an amplifier with a flat response, what would the sound be like?

Now read the answer

Comment

The sound would be very tinny, thin and lacking in bass notes. This is because when the disc is replayed by an electromagnetic pickup, the voltage output at low frequencies is reduced in level but at high frequencies is boosted. So to play any record using an electromagnetic pickup it is first necessary to set the replay amplifier characteristics to match the RIAA equalisation.

The Great Depression of 1929 caused considerable losses, with sales dropping to a tenth of their previous value. One by one the record companies went bankrupt or were taken over. In the UK in 1931, The Gramophone Company and Columbia merged to become Electrical and Musical Industries (EMI). By the end of the 1930s the market had begun to rally, with the realisation that radio broadcasting could be used to advantage through record promotions. In America jukeboxes, similar to the one shown in Figure 17, flourished and by 1939 over 13 million discs were sold just to stock the nation's 225 000 jukeboxes!

Figure 17: A jukebox from 1939

By this time also, many recordings now considered historically (and musically) important had been made by composers such as Elgar, Stravinsky and Rachmaninov. Many of the world's finest performers had also made recordings.

Following the Second World War (1939–1945), demand for records increased dramatically (supplies of shellac had been diverted to the war effort, so creating shortages of gramophone records – indeed, old records were recycled). An example of the upsurge is demonstrated by the figures for sales of an early recording of a popular piano concerto, which sold 102 copies in 1935 and 62 756 copies in 1946.

Record popularity was due in no small part to improvements in recording techniques. For example, an engineer at The Decca Company in England developed an extended frequency response as part of the war effort. The ‘full frequency-range recording’ (ffrr) technique gave a bandwidth from 30 Hz to 14 kHz; this ensured sounds of instruments included hitherto unheard harmonics, giving a much fuller sound.

Still, not everyone was happy with a technology that, apart from improvements in fidelity, had remained substantially unchanged since the early 1900s. Record consumers were no longer satisfied with excerpts of symphonies or musical works shortened to fit to one or two sides of a disc. Full-scale symphonies and choral works were available as sets. For example, Bach's St Matthew Passion (approximately three hours of music) came on eighteen double-sided 12-inch records, but listening to this work involved changing records 36 times, hardly convenient or indeed conducive to a fine musical experience!

In 1948 Peter Goldmark, head of research at Columbia Records in America, demonstrated a 12-inch (30-cm) non-breakable microgroove vinyl disc capable of playing 23 minutes each side. Columbia called it the LP (for long-playing) disc. It revolved at 33⅓ rpm with up to 300 tracks to the inch (120 per cm). The rival company RCA-Victor seemed not to be impressed with the LP. They responded with a 7-inch (18-cm) microgroove vinyl disc that revolved at 45 rpm, the so-called 45, which had a similar track pitch to the LP and played for up to 4 minutes. The ‘Battle of the Speeds’ commenced.

Activity 16

Can you suggest how the record-buying public responded to these two new ‘standards’?

Now read the answer

Comment

The immediate response from the record-buying public was to stop purchasing records until the outcome of the battle was decided!

Fortunately for all the record companies a truce was declared by 1950, with the 78 rpm disc the loser. The LP was adopted for classical recordings and the 45 for popular music. In Europe the change took a little longer, but by the end of 1952 LPs were available from European manufacturers.

The LP is not quite the end of the story of the gramophone record. As far back as 1931, the British engineer Alan Blumlein designed and patented a stereophonic (from the Greek meaning ‘solid sound’) recording system that used two sound channels to create a virtual sound ‘stage’ where an individual sound source (instrument, voice, etc.) could be located at any point between two loudspeakers placed at the front left and front right of the listener. The location of the source is determined by the relative intensity in the two channels. The patent covered two possible ways of cutting the groove in the record to allow two separate channels to be recorded. The V-L (vertical-lateral) method combined hill-and-dale and lateral cutting systems, whereas the 45/45 technique was similar except the cutter was tilted at an angle of 45° to the surface of the disc, putting the stereo signal into the groove walls, as illustrated in Figure 18.

Figure 18: The V-L and 45/45 recording techniques compared

In 1958 the 45/45 standard was adopted by the industry, having been patented in the United States by Westrex/Bell as early as 1937.

Activity 17

Can you think of a problem that existing record users might find with the introduction of stereo discs?

Now read the answer

Comment

Non-compatibility with existing monophonic (single-channel) systems meant the need to produce both mono and stereo discs. Retailers would have to stock both versions of the record. A stereo disc could be damaged if played on a mono pickup that was not designed to be compatible with stereo discs. This is because the stereo pickup needs to move in both the horizontal and vertical directions to cope with the 45/45 movement, whereas the monophonic pickup only moved horizontally; this could potentially cause damage to the stereo groove wall. Also not all the music information could be recovered by having a monophonic pickup. ‘Stereo-compatible’ monophonic pickups were eventually manufactured to overcome this problem, allowing the production of monophonic discs to be phased out.

This brings to a close the story of the record (cylinder and disc), the main source of recorded sound for nearly a hundred years. Apart from refining manufacturing techniques, little change to the technology took place. There is still a demand for vinyl discs from audiophiles, who believe the analogue sound cannot be surpassed. But it is DJs, who have made ‘turntablism’ an art form in its own right by creating new music by ‘scratching’ tracks from vinyl discs, that are keeping disc record playing alive. This demonstrates a use of the phonograph not even imagined by Edison!

Activity 18

Why are the following factors important in the quality of disc reproduction? What aspects of the quality of the reproduced sound do they affect?

The hole is exactly in the centre of the disc.
The disc lies flat on the turntable, not warped in any way.
The disc is made from a smooth material.

Now read the answer

If the hole is not in the centre the disc will turn eccentrically, causing variations in the linear speed and consequently changes in the pitch of the replayed sound.
If the disc is not flat there will be an audible noise every time the ‘bump’ is encountered. This will increase the signal-to-noise ratio.
The smoother the material the better the signal-to-noise ratio, as any ‘roughness’ in the groove will be reproduced as noise. (This is apparent when comparing the signal-to-noise ratio of 78 rpm discs made of shellac and slate dust, which is quite rough against the smooth plastic material of the LP.)

Your answers to the first two parts of the above activity should have described an effect known as wow. Wow is a low-frequency pitch variation that, in discs, can be caused not only by the spindle hole in the disc not being exactly centred or by the disc being warped, but also by slow variations in the disc motor speed. There is a second related effect called flutter, which is a higher-frequency pitch variation caused mainly by faster variations in the speed of the disc motor.

3.1 Introduction

3 Sounds from magnets

3.1 Introduction

I've an opera here you shan't escape – on miles and miles of recording tape.

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

Sounds, pictures, measurement data, financial statistics, personal details, etc. can all be recorded and stored on magnetic media, i.e. materials that are able to be magnetised to store information for future retrieval.

Activity 19

Construct a table of all the different types of magnetic media you think you may have used and what you kept on each type of media. Were you able to put any of the media to more than just one use, i.e. store different sorts of things on that media? Do not worry at this time if you are uncertain as to what I mean by magnetic media.

Now read the answer

Comment

The media types I thought of are shown in Table 2.

Table 2: Various types and uses of magnetic media

Magnetic media type	Use
Audio reel-to-reel tape	Music and speech
Audio cassette tape	Speech, music and computer data
VHS tape	Videos for television and digital audio
DV (digital video) tape	Home movies
Hard disk*	Computer data, music, speech, videos
Floppy disk	Computer data and music

Note: * There are two forms of the spelling. My convention will be that discs originally designed for music storage will be spelt with a ‘c’, whereas disks used for computer storage will be spelt with a ‘k’.

Did you notice from my list in the above activity that most magnetic media can have more than one use? I doubt that the designers of the compact cassette ever imagined it being used to store computer data (as was the case in the 1980s when cassettes were used with home computers). Magnetic media are incredibly versatile for recording and storing information due to their convenience of use, low cost, reusability and reliability, although not all these qualities are necessarily exploited. For example, audio and video recordings are often made only once and kept indefinitely, whereas data on a computer disk may be changed by the minute, as with the word-processor data file I am updating as I write (and rewrite!) this section of the unit.

3.2 Recording on the wire

3 Sounds from magnets

3.2 Recording on the wire

A paper published by Oberlin Smith in an 1888 issue of Electrical World discussed the possibilities for recording sound using the property of magnetism. He envisaged a cotton thread impregnated with steel dust passing through a coil carrying a current controlled by a microphone. The variations with the sound in the strength of the current would cause corresponding magnetic fluctuations in the magnetic medium. Unfortunately he dismissed his idea because, as he said in his paper, he thought that ‘the magnetic influence would probably distribute along the wire in a most totally depraved way’.

Smith's ideas remained theoretical as he never performed any experiments. However, by the end of the nineteenth century Valdemar Poulsen, a Danish electrical engineer, had demonstrated Smith's hypothesis. Poulsen's ‘telegraphone’, shown in Figure 19, was patented in 1898. It used steel wire wrapped around a brass cylinder as the magnetic medium. At the Paris Exposition of 1900, Poulsen made a recording of Emperor Franz Josef of Austria that is the oldest magnetic recording now in existence.

Figure 19: Poulsen's original wire recorder

The lack of appropriate technology meant that the telegraphone could not compete with the gramophone. The development of an electronic amplifier using the thermionic valve (vacuum tube) enabled the tiny magnetic fluctuations in the steel wire to be magnified to a usable level. By 1924 a German engineer, Dr Curt Stille, had developed a machine that could record sounds on a steel tape. The BBC (British Broadcasting Company) showed great interest for, at this time, they used disc recorders for pre-recording programmes and talks that were cut into acetate discs, replayed maybe twice and then discarded. So they sent two engineers to Berlin for a demonstration. They offered to buy the machine but were refused and so returned empty-handed. In 1931 Louis Blattner purchased a Stille machine, shipped it to England and renamed it the Blattnerphone, illustrated in Figure 20. It used 2-inch (50-mm) wide flat steel tape and could record for up to 20 minutes.

Figure 20: A steel tape recording machine

Taken from www.acmi.net.au/AIC/BLATTNER_STILLE.html

The BBC evaluated it but were unhappy with the signal-to-noise ratio due to a constant background hiss, caused by the physical qualities of the steel tape. Blattner eventually sold out to the Marconi Company, who in conjunction with Dr Stille further developed the recording machine. In order to provide a suitable audio bandwidth they found it was necessary to run the now one-inch-wide steel tape at a rate of 60 inches per second (152 cm per second). This meant that nearly 2 miles (3.22 km) of metal tape was required for a half-hour programme! Such was the pressure for an easy record and playback system that the BBC used steel tape recorders for a while, as demonstrated in the next activity.

Activity 20

Listen to the two audio tracks below. The first track contains a recording of the famous statement made by the Rt Hon. Neville Chamberlain on his return from Munich. This was recorded on a steel tape recorder in September 1938. As a comparison, the second track contains a 1932 experimental disc recording.

Notice the difference in background noise between the magnetic steel tape recording and the disc recording of 6 years earlier.

Click below (25 seconds)

Listen in separate player Click play to start.

Click below (1 minute 14 seconds)

Listen in separate player Click play to start.

Poor signal-to-noise ratio meant that steel tape was eventually discarded but one of the first home magnetic recording machines, the Webster wire recorder (described in Box 6), used thin steel wire, echoing Poulsen's idea.

Box 6: The Webster wire recorder

The Webster wire recorder was introduced in 1946 and remained popular with amateurs until the late 1950s.

The quality of this recorder was, for the time, surprisingly good – this was perhaps in part due to the fast wire speed of 30 ips (from which all the subsequent standard tape speeds – 15, 7½, 3¾ and 1 7/8 ips – were derived). Figure 21 is a photograph of the Webster wire recorder. The steel wire was 0.0036 inch in diameter and reels provided up to an hour of recording time.

Figure 21: A Webster wire recorder

3.3 Magnetic tape recorders

3 Sounds from magnets

3.3 Magnetic tape recorders

Experiments showed that the use of paper tape coated with iron oxide particles significantly improved the signal-to-noise ratio and enabled a lower tape speed to be used. A plastic-based version of this magnetic tape, developed by the German company BASF, led to the development of a commercial tape recorder with audio characteristics that could nearly match those of the gramophone record, but not at an economical price. Secret work on tape recorders was undertaken by the Germans throughout the Second World War. This was revealed when Allied forces captured the Radio Luxemburg studios in 1944 and discovered machines capable of outperforming discs in both sound quality and playing time. In America the Minnesota Mining Manufacturing Company (3M Co.) further refined the tape (their experience with adhesive tapes proved advantageous) while the Ampex Corporation developed a machine with a frequency response of 30 to 15 000 Hz at a tape speed of 7½ ips (19 cm/s) and a signal-to-noise ratio of 50 dB, certainly equalling, if not bettering, the characteristics of discs at that time. The tape speeds used for different recording characteristics are discussed in Box 7.

Box 7: Tape speed

The audio bandwidth of a tape recorder is determined to an extent by the selection of the tape speed, i.e. the rate at which the tape is drawn across the record and play heads, shown in Figure 22. The wavelength of the audio signal recorded onto the magnetic tape is proportional to the tape speed. As the tape speed is increased, a greater proportion of the tape is used to store the audio signal, allowing higher frequencies to be retained on the tape. Because high tape speeds are less economical on tape usage, tape recorders had speed controls to allow users to select the tape speed to suit the audio quality required, as detailed in Table 3.

Figure 22: The tape path on a tape recorder

Table 3: Tape speed vs bandwidth

Tape speed	Bandwidth	Use
38 cm/s (15 ips)	20 Hz–20 kHz	Studio recording
19 cm/s (7½ ips)	30 Hz–15 kHz	High-quality home recording
9.5 cm/s (3¾ ips)	40 Hz–13 kHz	General domestic music and speech
4.8 cm/s (1 7/8 ips)	50 Hz–6 kHz	Recording speech (dictation)

Soon tape recorders were in use by the American radio networks for pre-recording their broadcasts, the entertainer Bing Crosby being one of the greatest proponents of the technology. Recording companies were also quick to embrace the benefits of tape – especially the ease with which mistakes could be edited and retakes inserted. Also the ability to record for longer periods (30 minutes or more) meant less need for recording sessions to be split into short takes. Early domestic recorders were used primarily for playing stereo recordings, but they were costly in terms of both the hardware and the media: a pre-recorded stereo tape cost five times that of the equivalent mono LP disc. The sales of pre-recorded tape plummeted once stereo LPs became available in 1958. From that point on, domestic tape recorders (similar to the one illustrated in Figure 23) were used mainly by enthusiasts for home recording.

Figure 23: An enthusiast's home tape recorder

Activity 21

By referring to the information given earlier, construct a table that compares the frequency response and playing time of the newly developed magnetic tape with that of 78 rpm discs of the same period (1945).

Now read the answer

Table 4: Comparison of 78 rpm disc and magnetic tape media

Characteristic	78 rpm disc	Magnetic tape
Frequency response	30 Hz–8 kHz	30 Hz–15 kHz
Playing time	5 minutes per side	30 minutes (minimum)

Tape could offer twice the bandwidth and six times the playing time.

The frequency response of magnetic tape was between 30 Hz and 15 kHz, and the playing time was up to 30 minutes. The frequency response of a 78 rpm record was 30 Hz to 8 kHz. The playing time was up to 5 minutes for each side of a 12-inch (30-cm) disc.

3.4 Compact cassettes

3 Sounds from magnets

3.4 Compact cassettes

The use of magnetic tape for home use has always been somewhat problematic. Whilst it offers several advantages over discs, being capable of high-quality sound, substantially free from surface noise and able to make personal recordings, tape never became so popular as to make any serious inroads into the sales of discs. Why should this be the case? The answer is one of convenience, for magnetic tape has always been difficult to handle compared with discs – threading the tape through the machine and onto the take-up spool was a fiddly process, and the tape could easily get damaged or snap.

Many companies developed tape cassette systems based on standard quarter-inch tape but none succeeded in gaining acceptance by consumers. The compact cassette system, shown in Figure 24, was developed by Philips Gloeilampenfabrieken in 1963 for recording speech (shades of Edison!). Philips called their cassettes compact to distinguish their system from other audio cassette systems and they made no pretence of achieving high-quality sound, deciding to use a slow tape speed (1 7/8 ips) and a new narrow one-eighth-inch-wide tape to keep the whole system as small as possible. The convenience of slotting cassettes into the machine rather than having to thread tape around guides and tape heads made this format much more suitable for consumers.

Figure 24: A Philips audio cassette recorder with a compact cassette

To use the compact cassette system in place of vinyl LPs necessitated overcoming two obstacles: first, the limited bandwidth due to the low speed, and second, the poor signal-to-noise ratio because of the low signal level output from the narrow tape. The bandwidth was increased to a degree by the use of special magnetic tape formulations, including high-density ferric oxide, chromium dioxide and pure metal compounds. The signal-to-noise ratio was also improved because these tapes allowed signals to be recorded at higher levels. However, the poor signal-to-noise ratio was really only solved by the Dolby Laboratories, who developed and licensed a consumer version of their professional noise-reduction system, Dolby A. The Dolby B noise-reduction system described in Box 8 dramatically improved the sound quality on compact cassette tapes, enabling them to rival discs. Remember that although Dolby B encoding can reduce tape hiss, it cannot be used to improve the quality of the original recorded sound.

The ability to make Dolby-encoded home recordings was a very attractive feature of the system and certainly contributed to the wide acceptance of the compact cassette. This was exploited particularly in automobile audio systems where a copy of an LP or CD could be played whilst driving. Sales of classical music compact cassettes overtook LPs by 1983 but were themselves overtaken by CDs in 1988. By 1994 classical CDs took 78% of the market, compact cassettes 21% and LPs a mere 1% (data from the Statistics Handbook (1995), The British Phonographic Industry, London, p. 21).

Box 8: The Dolby B noise-reduction system

Dolby Laboratories developed their Dolby B noise-reduction system to improve both the frequency response and the signal-to-noise ratio of the compact cassette system.

Magnetic tape can hold only so much signal; beyond this it will saturate (i.e. the magnetic particles on the tape cannot be magnetised any more). The louder the signal being recorded, the closer the tape becomes to being saturated. For a particular tape recorder and tape the amount of tape hiss is constant. Thus the louder the wanted sound, the less obtrusive the hiss will be. However, if loud (high-level) signals are recorded and at the same time boosted significantly for the purpose of noise reduction, the tape would saturate and the recording would become distorted.

The basis of the Dolby noise-reduction system is that low-level high-frequency signals are boosted when the recording is made, and the opposite process is carried out on replay. The process is applied only to high-frequency signals, as this is the frequency range where the hiss is most obtrusive.

To boost the noise-reduction effect further, the Dolby B system uses a sliding range for the frequency where the signal boost starts to happen. When the sound signal is very low or contains few upper frequencies, the boost start point slides to its lowest frequency, giving on replay a maximum of 10 dB noise reduction above 4 kHz. As the sound level increases and/or there are more higher frequencies in the signal, the start point frequency rises and so the perceived reduction in noise on replay is reduced; but of course because the signal is louder in the upper frequencies, the hiss is less noticeable.

The key to successful operation of this system is in the positioning of the sliding bands, and the ability of the decoder in the replay machine to track these changes in frequency and so reproduce exactly the original signal. If, for some reason, the frequency response of the encoded signal is changed before it reaches the decoder, mis-tracking of the sliding bands will occur. How audible this becomes has to do with several factors, including the nature of the music, the listening conditions and the sensitivity of the listener. However, audible effects of mis-tracking are minimised by limiting the overall boost range to 10 dB.

Activity 22

Disc recordings have always had a specific advantage over tape when it comes to accessing a particular part of a recording. By describing the different technologies used to store the sound, can you suggest what that advantage might be?

Now read the answer

On the tape the sound is recorded as a series of magnetic fluctuations along its length. In order to get to a particular part of the recording the tape must be wound forwards or backwards. This may take several minutes, especially if the required sound is at the other end of the tape.

On discs the sound is also recorded serially as a single spiral track. However, to find the equivalent sound on a disc is a relatively quick operation, performed by simply placing the pickup at the appropriate place on the disc surface. This takes the same time no matter where it is on the disc. The speed and ease of access to particular songs has always given an advantage to the disc over tape as a commercial replay medium.

Activity 23

Listen to the audio track below. You will hear an original live digital recording made at The Open University especially for this activity. During the recording four different formats were used: direct digital, an original compact cassette tape without noise reduction, the same tape with Dolby B noise reduction and a metal-compound cassette tape again with noise reduction. Listen carefully to the differences in the quality of the recorded sound.

Note: the differences are quite subtle and you may find them easier to distinguish using headphones (but remember to check your volume levels first if you are switching to headphones).

Click below (1 minute 38 seconds)

Listen in separate player Click play to start.

Now read the answer

Comment

I expect you noticed the very intrusive tape hiss after about 18 seconds. I am sure you agree this is unacceptable for most music recordings although it could be tolerated for speech. The tape hiss is reduced to an acceptable listening level after a further 25 seconds by using a Dolby B noise-reduction processor. This cuts the tape hiss by about 10 dB but maintains the tonal balance of the sound. This would not be possible using conventional filters (e.g. treble-cut tone controls), which although they would suppress the tape hiss would also affect the tonal balance of the sound. Finally, after a further 30 seconds the tape hiss becomes almost inaudible through the use of a metal compound cassette tape and Dolby B noise reduction. This combination cuts the hiss by a further 10 dB, making the overall sound quality very close to the original digital recording at the beginning of the track.

3.5 Studio tape recorders

3 Sounds from magnets

3.5 Studio tape recorders

The importance of tape recording to record production cannot be overemphasised. From its development until the coming of digital tape recorders in the late 1970s, the analogue tape recorder was at the heart of the professional music recording studio. Initially, the full width of the standard quarter-inch tape was used for making monophonic recordings. Stereo needed two tracks – one for each channel. Rather than doubling the tape width, a decision was made to halve the track width by incorporating two discrete heads one above the other in a single head assembly. This reduced the signal-to-noise ratio by 3 dB because of the reduced output signal from the replay head. As technology advanced, more tracks were able to be added whilst keeping the noise to an acceptable level. By also widening the tape, even more tracks could be incorporated so allowing individual instruments to be recorded on separate tracks for down-mixing at a later date. Figure 25 shows a professional 24-track analogue tape recorder using special 5-cm (2-inch) wide tape.

Figure 25: A professional 24-track analogue tape recorder

Ampex GB Limited

These complex machines are capable of reproducing high-quality sound for each track with a bandwidth equalling the average human ear and they represent the pinnacle of analogue multitrack tape recorders.

Activity 24

Why is it important that the plastic backing material of magnetic tape be as resistant as possible to stretching?

Now read the answer

Comment

The effect of stretching the tape is to make it longer. This means that it takes more time for the original length of tape to pass the head, effectively slowing the tape speed. The pitch of the signal in the original recording will consequently be lowered.

4 Unit summary

Sound recording really took off once the public's demand for recorded music had been acknowledged. The choice of technology, cylinder or disc, was determined more by the selection of the artist and material than the quality of the sound. Development of disc technology was slow due to the lack of better alternatives, remaining substantially unchanged for over fifty years. The development of radio broadcasting caused a slump in the record industry but eventually it not only provided improvements in recording technology, by replacing acoustic recording with electrical methods, but also became a shop window for records. Once perfected, magnetic tape offered a superior sound quality to 78 rpm records and spurred the record industry into developing the long-play vinyl disc, which improved the quality of sound and, most importantly, increased the playing time. Difficulties in operating conventional tape recorders led to the development of the compact cassette, sales of which overtook LPs once the sound quality had been improved by the Dolby B noise-reduction system.

Then I never did care for music much – It's the High Fidelity!

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

Activity 25

To round off this unit on the history of sound reproduction on a lighter note, listen to the audio track below. This is the complete version of ‘The Song of Reproduction’ by Michael Flanders (1922–1975) and Donald Swann (1923–1994), performed by the composers in a live recording from the late 1950s of their popular At the Drop of a Hat comedy show.

Click below (2 minutes 39 seconds)

Listen in separate player Click play to start.

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Acknowledgements

The following material is Proprietary (see terms and conditions) and is used under licence

Figures

Figure 7: The Royal Scottish Museum, Edinburgh

Figure 8: The Royal Scottish Museum, Edinburgh

Figure 20: taken from www.acmi.net.au/AIC/BLATTNER_STILLE.html

Figure 13 and 25: Ampex GB Limited

We also thank Nigel Bewley (British Library Sound Archive), Daniel Leech-Wilkinson (King's College, London) and Robert Philip (The Open University) for advice on the restoration of recordings; Stephen Potter for loan of the 78 rpm disc set of the Elgar Violin Concerto; and Bill Strang for playing the piano for Activities 17 and 26.

Every effort has been made to trace all the copyright owners, but if any has been inadvertently overlooked, the publishers will be pleased to make the necessary arrangements at the first opportunity.

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