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 throug
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 thou
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 th
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. Note: This optional activity requires the use of a 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 Author(s): Module team
Academic staff
Dr Alec Goodyear (course chair) Professor Nicholas Braithwaite Jan Kowal Dr Tony Nixon Dr Sally Organ Robin Harding (critical reader) James McLannahan (critical reader) Dr Martin Rist (critical reader) Dr George Weidmann (critical reader) Peta Jellis (course manager) P Acknowledgements Grateful acknowledgement is made to the following sources:
Figure 7 (a): PDB ID 1BKV Kramer, R. Z., Bella, J., Mayville, P., Brodsky, B. and Berman, H. M. (1990) ‘Sequence dependent conformational variations of collagen triple-helical structure’, Natural Structural Biology, vol. 6, pp. 454–57
Figure 7(b): PDB ID 1ATN Kabsch, W., Mannherz, H. G., Suck, D., Pai, E. F. and Holmes, K. C. (1990) ‘Atomic structure 4 Engineering with proteins What are the prospects for designing and making new proteins for specific purposes? The technology exists to build polypeptide chains unit by unit in a test tube, but this is time-consuming and expensive. Often a more practical approach is to find ways of working with nature to produce useful substances in a form that we can use. This might involve extracting a naturally occurring protein and chemically modifying it in some way, or using genetic engineering to produce a particular protein in 3.1 Protein diversity Of course, our bodies can't just be made up of squidgy bubbles of phospholipid, or we would collapse in a heap on the floor! Stiffer frameworks, both inside and outside the cells, also exist and help to define shape and add strength. These frameworks are formed largely from structural proteins, a class of polymeric materials that form fibres and filaments to provide mechanical support for cells and tissues. Structural proteins are made inside cells but are often then moved into the spa 1 Biological materials Materials engineers have long recognised the impressive range and combination of properties offered by biological materials. Figure 1 shows some representative examples of the combination of tensile strength and toughness (measured by Young's modulus, or elastic modulus for polymers) offered by natural mat Acknowledgements Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: 5.14 Response and damping You have learned so far in this chapter that when a musician plays an instrument, they force the primary vibrator to vibrate. If the primary vibrator is driven at one of its resonance frequencies, the normal mode of vibration corresponding to that resonance frequency will be excited. Now, in practice it is also true to say that even if the primary vibrator is driven at a frequency close to the resonance frequency, the normal mode will still be excited, but just to a lesser degree. In other wo 5.12 Vibrating air column: pitches of notes produced by wind instruments In a wind instrument, the air column is the primary vibrator. To excite the air column, a musician either blows across it (e.g. flute) or blows down it via a mouthpiece (e.g. trumpet) or reed (e.g. oboe). This supplies energy, which starts the air column vibrating. The air column isn't just forced to vibrate in one single mode; as with the string, it vibrates in a combination of several modes. To a good approximation, the air column of a flute is cylindrical with two open ends and, as a 5.4 Vibrating string: normal modes of vibration The frequencies at which standing waves can be set up on a string are the string's natural frequencies. They can be determined quite easily. The first thing to note is that the end of the string being held by the person is tightly gripped so any pulse or wave that returns to the person's hand will be reflected and inverted. Therefore both ends of the string can be considered to be fixed and so must be at nodes of the standing wave. But you learned earlier that the distance between adjacent no Learning outcomes By the end of this unit you should be able to: Explain correctly the meaning of the emboldened terms in the main text and use them correctly in context; Identify whether a given sound source can be classed as a musical instrument and explain why (Activity 2); Identify the primary vibrator and any secondary vibrators in the most common types of instrument (Activity 3); Appreciate that, when a note is played, a musical ins Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: This extract is taken from TA212. © 10.4 Summary The decibel (symbol dB) is a way of expressing a ratio. It is based on logarithms, and so adding decibels is equivalent to multiplying their corresponding ratios. Decibels can be used to express absolute values by referring them to a reference value. A common use of decibels is to express ratios of amplitudes. For instance, the amplification (or gain) of an amplifier can be expressed either as the ratio of the output and input amplitudes, or as a certain number of decibels. With a multi 9.1 Frequency range The lowest frequency humans can hear is approximately 20 Hz. The upper limit for humans is nominally 20 000 Hz (20 kHz), but this limit tends to decline with age, and for most of us it is well below this figure. 8.3 Summary A fundamental musical and acoustical relationship is the octave. Pitches that are one or more octaves apart are heard musically as different instances of the same sound. A one-octave increase in pitch corresponds to a doubling of frequency. For musical purposes, a pitch range of one octave is divided into discrete steps, known as scales, the individual pitches of which are given letter names (A, A 8.2 Octave pitch and frequency increments Because a doubling of frequency corresponds to an octave increase of pitch, it follows that there is no constant increment of frequency that always corresponds to a one-octave increment of pitch. That is to say, there is no fixed amount by which a frequency can be augmented that will always produce a one-octave pitch rise. For instance, starting at the pitch A4 with a frequency of 440 Hz, we need to augment the frequency by 440 Hz to get the pitch one octave above (880 Hz). B
Activity 1 (Optional)
T356 course team
External assessor
Figures
Author(s):
Audio Materials
Activity 27 (Self-Assessment)
