10.3 The decibel as a measure of sound amplitude As I mentioned earlier, because a decibel is a way of expressing a ratio, it cannot by itself express the absolute size of anything. To express absolute values it must be referred to a fixed reference quantity, against which whatever is being measured can be compared. In the context of acoustics the reference used is the lower limit of audibility – the threshold of audibility. This varies from person to person, but has a nominal value that can be expressed as a pressure wave with an
10.1 Introduction For a variety of reasons, not least the very wide dynamic range of human hearing, the decibel (symbol dB) is often used as a unit for the amplitude of sound waves. The decibel is also used in other contexts, such as specifying the amplification of amplifiers or the degree to which a signal is affected by noise. In the context of sound, the use of the decibel as a unit captures something of the subjective impression of the way loudness changes with amplitude. The decibel unit has
6.1 Defining amplitude Another important property of a sine wave we need to be able to specify is its amplitude. In essence, the amplitude of a sine wave is its size. Unfortunately there are various ways of defining what is meant by the size of a sine wave, and you are likely to come across many of them in material you look at outside this unit. Before I explain what our definition is, it will help matters if we look at what is meant by the average value of a sine wave. Figure 16 shows a sinusoidally a
1.3 Describing sound Let's now take a closer look at my list of categories from Activity 3, starting with item (a). In each of my descriptions of this sort, I referred to the source–cause of the sound: that is, an object or an instrument (the source of the sound) and ways of using it to produce a sou
7.2.4 Trap 4: words and wordiness I have seen some effective rich pictures with lots of words in them but they are quite rare in my experience. More often, lots of words make the rich picture less rich. Part of the later use of a rich picture might include looking for patterns. Words inhibit your ability to spot patterns. If you do use speech bubbles, use what people say, not your interpretation, unless the bubble is about some general attitude. Examples might be ‘Aaagh!’, ‘Help!’, ‘Oops!’ – the sort of th
2 Part 1 Starting the unit Welcome to T306_2 Managing complexity: a systems approach – introduction. As I write, I experience a sense of excitement. For me, as for you, this is the beginning of the unit. These are the first few sentences I'm writing and so, although I have a good idea of how the unit is going to turn out, the details are by no means clear. Nevertheless, the excitement and anticipation I, and maybe you, are experiencing now is an important ingredient in what will become our experiences of the u
13 Part 2: 4 Preparing for innovation Many inventors have said that having the idea for an invention is the easy part. This is often demonstrated by the frequency of examples of simultaneous invention. At one exhibition of inventions I attended there were three separate portable ladders to escape from fires, two systems for using rainwater to flush toilets, two types of portable vehicle wheel clamp, and two methods of reducing red-eye in flash photography. In most cases of technological innovation only one of the competing techno
10.5 Desire to help others This is a less common motivation but it shows not everyone is driven by money. In 1991 the inventor Trevor Baylis saw a BBC documentary about the spread of HIV/AIDS in Africa. What was needed was a way of broadcasting the safe-sex message to people in areas without electricity and where batteries for a radio could cost a month's wages. Solar power wouldn't necessarily help as most people who could get to a radio listened in the evening after work. While absorbing this information he ima
9 Part 2: Invention Having taken a broad look at the whole innovation process from invention to diffusion, I'll go back and look more closely at what motivates individuals and organisations to invent. Then I'll consider how people generate ideas for inventions and the designs based on the inventions.
4.4 What was innovative about the telephone? The most obvious innovative aspect was that speech was being transmitted, so in principle anyone could use a telephone for communication. The use of the telegraph required skilled operatives. A message had to be translated into the dots and dashes of Morse code and transmitted using a single keypad making and breaking the connection in an electrical circuit. At the other end of the wire another Morse operator translated the received clicks into the words of the message. With the telephone no
1.2.2 Visualisers and verbalisers A major point about diagrams is that some people naturally relate well to them and use them frequently, while others tend to prefer textual material. The former are sometimes referred to as visualisers and the latter as verbalisers. There is nothing wrong with either of these tendencies, but in subjects like systems thinking, social science or technology, where text and diagrams support each other, it is important to be comfortable with both. In addition, it is helpful to rememb
1.1.3 Features of diagrams As there is variety in the types of diagrams we can see and use we need to think more broadly about what diagrams are trying to represent. One distinction which follows on from the discussion above is:
Analogue representations: these diagrams look similar to the object or objects they portray. At their simplest they are photographs of real objects and at their most complicated they are colourful, fully labelled drawings of the inner workings o
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4 Who are the users? This section reveals that ‘users’ can include a wide variety of people – not just the final purchasers or consumers of a product. The section also makes the case for strong user representation in the design process. Of course, it is not only me who uses the various products in my home; other people use them as well, both members of the family and visitors. Sometimes the range of users of a product, and their different needs, can be diverse. And in addition to the obvious or intend
5.8.1 Nitrate removal Nitrate in water has become a significant problem and the EU Directive sets a maximum admissible concentration of 50 g m−3 measured as NO3−. This is equivalent to 11.3 g m−3 as N. High nitrate levels can cause cyanosis or methaemoglobinaemia in babies. Legislation allows the designation of nitrate-vulnerable zones and these help to prevent nitrate levels in natural waters increasing in affected areas.
Ion exchange is used in some
5.6 Filtration In filtration, the partially treated water is passed through a medium such as sand or anthracite, which acts as a 'strainer', retaining the fine organic and inorganic material and allowing clean water through. The action of filters is complex and in some types of filter biological action also takes place. Sand filters are used in water treatment to remove the fine particles which cannot be economically removed by sedimentation. They have been effective in removing Cryptosporidium, a pr
1.7 Conclusions Could both of these students have got more from their involvement with the course if they had taken time to reflect on their goals and their strengths and weaknesses, especially at the beginning of study? Alan, whose reaction to the course was positive, for example, could have learned more about how the course succeeded if he had reflected rather more in the beginning about his initial scepticism and his preference for communicating verbally rather than in writing. What was the reason for his
1.4 Defining reflection Reflection is both an academic concept and also a word in common use, combining ideas of thinking, musing, pondering and so on. This everyday meaning is a good basis from which to start: reflection is very much to do with thinking. However, one of the most important things about reflection is that it enables us to think about our own thinking – about what it is that we know or have experienced. Such reflection might be summed up in the phrase, 'the mind's conversation with itself'. Wh
1.2 Learning beyond course study Learning how to learn has become an important goal in higher education. There is a national context in which an emphasis on ability to learn has come to prominence. It is now widely asserted that an ability to learn is as important an outcome of university study as knowledge of a discipline. This is a view put forward strongly by employers, for example, who have an interest in the employability of graduates and the skills they bring into the work place. It is a view which has been reiterated
1.1 Effective course study Research into how people study effectively suggests that it is important to pay attention not only to the content of what we are trying to learn but also to the process of our learning. Time spent on the process of how you are learning need not be a distraction from achieving your learning goals. It should support your efforts to achieve them. However, thinking about the process of your own learning is not something which typically forms part of most formal courses of study. Most people
