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 appa
Author(s): The Open University

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:

## Author(s): The Open UniversityLicense informationRelated contentExcept for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

In this section I am considering sine waves that have the same frequency, but are out of step with each other.

Suppose we have two detectors at fixed points, A and B. At this moment in time A is in a high pressure region and B in a low pressure region. If we were to look again shortly later B would now in a high pressure region and A in a low pressure region. The pressures at A and B would be out of step with each other. The pressure variation at B is not in phase with that at A. The ex
Author(s): The Open University

The speed of sound in air, symbol v, is approximately constant at 340 metres per second. (You do not need to memorise this value.) As temperature increases, the speed increases slightly.

Speed, frequency and wavelength are related by the formula v = f Ã— Î». Other forms of this relationship are f = v/Î» and Î» = v/f. Because the speed is approximately constant, it follows that frequency and wavelength are inversely pr
Author(s): The Open University

One way to establish the speed of sound is to measure it experimentally. That is, one measures how long the sound takes to travel a known distance, and from this works out the speed. The answer turns out to depend somewhat on the prevailing temperature and humidity. At an air temperature of 14 Â°C the speed is 340 metres per second and at about 22.5 Â°C it is 345 metres per second. That is a change of speed of less than 1.5 per cent for an appreciable change of temperature. To a reasonable ap
Author(s): The Open University

Pressure in the air is related to how closely packed the molecules are. Other things being equal, more closely packed molecules are at a higher pressure than more dispersed molecules. Sound is associated with fluctuations of the air pressure caused by local disturbance. Fluctuations of pressure travel outwards away from the disturbance, carrying energy imparted by the disturbance.

A simple form of local disturbance to air pressure is a vibrating tuning fork. It generates a pressure wave
Author(s): The Open University

In this section we shall be looking at the behaviour and properties of pressure waves in the atmosphere.

Sound originates from the motion or vibration of an object. Let's look at an example of a sound wave generated by a vibrating tuning fork. The prongs of the tuning fork move backwards and forwards cyclically. A cycle is a complete series of movements up to the point where the movement starts to repeat itself. As the prongs of the fork vibrate back and forth they push on neighbouring
Author(s): The Open University

In the previous section I posed a question: what is sound? Take a few minutes to think about this. This may seem a straightforward question, but in fact sound is a rather more complicated thing to pin down than you might think on a first analysis. In this section I would like to explore and map out this complexity, and we shall do this together, based on your own experience with sound. To start, I'd like to propose some listening activities.

Author(s): The Open University

Music technology in one guise or another is part of everybody's life, because music is a part of almost everybody's life. For instance, if you are an instrumental performer of music, professional or not, then your instrument, be it the harp or the rock'n'roll drums, will be the result of considerable technological expertise on the part of the instrument maker. On the other hand, if you are not a performer but like to listen to music, the chances are that most of your listening is done via a h
Author(s): The Open University

After studying 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;

• describe simply what a pressure wave is and give a simple explanation of sound in terms of a travelling pressure wave;

• explain â€˜cycleâ€™ in terms of an oscillating source and the pressure wave it produces;

• relate amplitude (including peak-to-peak and r.m.s.), frequency, period a
Author(s): The Open University

When I first described some of my experiences of the child-support case study above, I attributed the properties of mess, complex, or hard-to-understand to the situation. So, are mess, complex, and hard-to-understand the same thing? If they are, why is the unit called Managing Complexity, rather than, say, Managing Messes? A glib answer is you might not have been attracted to it because of the everyday meaning of mess. Yet another answer is that complexity is a rich term whose everyday meanin
Author(s): The Open University

The metaphor of the juggler keeping the four balls in the air is a powerful way for me to think about what I do when I try to be effective in my practice. It matches with my experience: it takes concentration and skill to do it well. But metaphors conceal features of experience, as well as calling them to attention. The juggler metaphor conceals that the four elements of effective practice often seem to be related. I cannot juggle them as if they were independent of each other. I can imagine
Author(s): The Open University

Multiple-cause diagrams are another way of using interconnectedness to structure a complex situation. In this case, the interconnectedness is that of causation. Multiple-cause diagrams represent both sufficient and contributory cause, without making a distinction between them. Drawing multiple-cause diagrams allows for the identification of systems of causation. Such a system can be pictured as an interconnected group of events or effects; the effect is of a system that behaves
Author(s): The Open University

I want to return to the definition of a system I used earlier: an assembly of components interconnected as if they had a purpose. In the last section, I used purpose as a way of structuring the complexity of the case study. In this section, and the sections that follow, I want to turn to the idea of interconnectedness as another way of structuring the complexity. In the case of influence diagrams, I search for interconnection in the form of influence to hold together a structure
Author(s): The Open University

Before moving into a discussion of the missing element of the rich picture, I want to direct your attention to all the thoughts and ideas I have encouraged you not to put into your rich picture. I imagine you might have collected quite a list of loose ends. The next activity will involve some of these.

Expect to take about half an hour to do the next activity.

Author(s): The Open University

I hope that, by now, you have a rich picture you are pleased with. This is a considerable achievement because, despite the informality of the rich picture's style, a rich picture that effectively captures the complex situation takes a lot of effort to achieve. It depends crucially on being prepared to enter into the experience of the situation of interest and to interrogate that experience thoroughly. Noticing is not enough. Each feature of the situation has to be carefully captured by repres
Author(s): The Open University

Remember to date your rich picture and not to throw away any previous versions. Old versions of rich pictures provide you with a record of your developing understanding.

The next activity is an invitation to improve your rich picture by digging yourself out of any of the traps you may have fallen into. In this activity, I suggest a certain ruthlessness in reviewing your efforts so far. You should not, however, see this as an evaluation of your performance in the task. My experience is t
Author(s): The Open University

A distinguishing feature of rich pictures that turn out to be useful seems to be they are just what they say they are, rich. If I take usefulness as the criterion, the useful rich pictures are the ones bursting with interest and activity. They don't seem to tell a single story, there are lots of stories going on simultaneously. They reveal stories you didn't consciously build into them.

How is such a rich picture to be achieved?

Use everything you find in the situation. This means
Author(s): The Open University

This trap is one of the most fundamental mistakes you can make in systems thinking. There are lots of metaphorical phrases in English that can entice you into the trap. We can talk about â€˜the nub of the problemâ€™, â€˜the key issueâ€™, â€˜the basic problemâ€™, â€˜the real difficultyâ€™ and so on.

Like all traps, once it has sprung, it can be very difficult to get out. The trap seriously limits one's ability to think about the situation in its full complexity. This is precisely because
Author(s): The Open University

This section is mostly concerned with thinking about your rich picture and the complex situation it depicts.

There are lots of ways of drawing a good rich picture and very few ways of drawing bad rich pictures. So my next strategy in supporting your learning, and your experience of this complex situation, is to propose a number of checks you might use to ensure you have not fallen into the trap of the less-effective rich picture.

Although my discussion will focus on rich pictures,
Author(s): The Open University