INTRODUCTION to the First Edition

No field of study based on sensory experience seems to be overburdened by terminology to the same extent as that dealing with sound and hearing. The visual sense, of course, has received as much attention as the auditory from physics, psychology, neurophysiology, and the visual arts, which have all contributed terminology and jargon alike, but a great deal of it seems to have entered the common vocabulary already, and at least the general notions involved are seldom foreign to the average citizen or student. Terms such as perspective, foreground, background, colour, spectrum, shadow, focus, image, reflection, transparent, translucent and the wealth of descriptive visual terms, not to mention common visual impairments and the complexity of visual language found in contemporary cinema and photography - all of these have found public familiarity in a way that it is hard to imagine their sonic counterparts ever matching. Almost every school child knows what white light is, and how it is composed, but would he know what white noise is, even though the likelihood of it having an adverse effect on him is far greater? The ability to perceive three-dimensional visual perspective when projected onto a two-dimensional surface, by no means a simple achievement given the lateness of its appearance in our civilization, is irrevocably ingrained in the child's perceptual habits at an early age, and yet the ability to distinguish acoustic parameters, or experience subtle nuances of timbre (supposing he knows what timbre, the sonic equivalent of colour, is) may never be among his perceptual skills.

As researchers into every aspect of the acoustic environment, we feel that this paradox reveals the tendency of our culture to trade its ears for its eyes, that is, to rely more heavily on visual information and less and less on aural cues. One reads of blind people a few centuries ago leading normal, productive lives, compensating for their lack of visual sense by an amazingly acute aural faculty, and yet today the obliteration in both urban and rural environments of the subtle acoustic information that allowed such normal orientation and activity has turned this deficiency into a handicap. The areas now barred to these people (operating a motor vehicle, visual media, many industrial and scientific occupations, the many aspects of formal education now made difficult) reveal fundamental biases of our culture toward the visual in its vital institutions and conventions.

The same bias is abundantly apparent in the ways our society has contrived to talk about sound. Most of the visual terms already mentioned have been taken over directly into the sound vocabulary or translated analogously [compare AUDIOCENTRIC]. Colloquial language is similarly invaded: "Seen in this light, one must review each person's background, you see, and focus attention on putting the entire spectrum of viewpoints into perspective, having the foresight to overlook no apparent alternative that would cast a visible shadow of doubt or reflect an inability to make one's basic outlook transparently clear from any vantage point."

While the visual bias of such cliches may be merely amusing, the negative effects of the sonically imbalanced living environments of the world's industrialized nations are not. It is our contention that the cause of this predicament can be traced to the public's waning auditory skills - a basic inability to hear clearly by those responsible for this imbalance, by which we mean to include as much the citizen who buys noisy appliances and vehicles, as the architects who build noise into their (visually and structurally) advanced designs, and the manufacturers who do the same with products that are thoughtlessly unleashed into the sonic environment regardless of their harmful effects.

The majority of terms in this document have appeared within the last century, at about the same rate as the degeneration of the soundscape. The tragedy is that they seem to have been used and proliferated to divert attention from the real problem (which was obvious enough to anyone willing to listen carefully), and to convince the populace that its ears were inadequate tools for assessing the situation, and that such problems might better be left to professionals who knew how to build better meters and devise increasingly complex systems of measurement for what they had already stopped listening to. Among the countless examples, here is a definition offered in a publication of the U.S. Environmental Protection Agency1:

SONIC BOOM - The pressure transient produced at an observing point by a vehicle that is moving past (or over) it faster than the speed of sound.

Note the paradox whereby, on the one hand, the phenomenon is defined physically (as a pressure transient), and not perceptually (as something heard), but on the other hand, it is implied that it only exists "at an observing point" (i.e. a measurement site) and not, as is the case, along a path hundreds of miles long. Moreover, we are asked to imagine a hypothetical terrestrial vehicle breaking the sound barrier; it is only admitted parenthetically that the boom might be caused by something flying overhead. Although the definition is technically accurate, the disparity between the devastating reality of this recently invented sound and the jargon of this definition can only be ascribed to its author having conducted his research in an underground bunker during the last sonic boom in his area!

During the last ten years, the term 'noise pollution' has entered the common vocabulary, long after it had in fact become a reality, and along with increasing public awareness and outcry has come a huge body of research on the harmful effects of noise. We have attempted in this volume to include as many of the terms and systems for noise measurement as we have been able to find documented. The list is staggeringly long, and seems to be increasing every year. All seem premised on the assumption that more elaborate statistical procedures will bring us closer to measuring what is happening and its effects. All of them exchange the reality of the sound for an array of arbitrary numbers, then compare them to an equally arbitrary scale as to what amount of noise is tolerable for bedrooms, libraries, multiple family housing areas, and so on, so that airports, freeways and industries can be allowed to do what they wish as long as the numbers fall within the right limits. In our opinion, all of these systems are circumventions of the real problems of noise, and that the time has long since passed when local governments, anti-noise committees, and the general public should be cowed by the labyrinth of measurements to the point where they can only recommend that more study needs to be done. Millions have already been spent on such research and studies, and the results go largely unheeded; more listening and imaginative thinking are the only things that still need to be done.

Our intention, then, of exhaustively including all such terms is to bring their number and attitude to the reader's attention, with some detail on how they operate so that they may be defeated on their own ground. All of these systems treat the sonic environment as an object on which increasingly complex measurements may be carried out. They all isolate sound from the way in which human beings understand it. In any of these measuring systems, no matter how sophisticated, one sound is treated similarly to any other sound; there is no way to distinguish what meaning the sound has for those making or hearing it, what associations or symbolism it may have, how it may be understood to fit in or not with other sounds, whether it is perceived as background or foreground, wanted or unwanted. In other words, any such device or system treats sound as a signal to be processed, instead of information to be understood. No human intelligence is built into such a system, and yet it is only by discovering how the mind organizes sound input that any assessment of a soundscape may be made.

One trend in noise measurement today is to introduce modifications into the system in question so that it supposedly takes human reactions into consideration. All of these are only marginally useful since the model of human behaviour on which such modifications are based is overly simplified and scientifically out-of-date as well. For instance, sound level meters have for some time now been given a weighting network (the 'A' network) so that they react to loudness depending on the sound's frequency in much the same manner as do the ear and brain, that is, low and very high frequencies are not heard as loudly as those in the middle range. By doing this, first of all, infrasonic vibrations are ignored (that is, those below the lowest perceived pitch, in the range where sound is 'felt' as movement of the air rather than heard). These vibrations have been shown to cause feelings of nausea, tiredness and various physical disorders. At the other end of the frequency range, those near and above the audible limit are also excluded, and yet they have a pronounced effect on the human nervous system. The region where the ear is most sensitive (about 1 to 4 kHz) is not given any special consideration with such meters, even though sounds with a great deal of energy in that region, such as those made by most motors, are extremely annoying and exhausting for the individual. Various more sophisticated systems do consider this latter aspect, but neglect the sound's behaviour in time as well as the previously mentioned considerations.

Other systems use statistical data derived from social surveys to predict community annoyance, and yet such data has been collected from people who have learned to shut out the very kinds of sound whose effect these measurements are trying to assess. The circle continues: the more noise, the greater the barriers of perception people are forced to raise, the less annoyance they will profess, the higher will be the allowable noise the community will be thought to tolerate, and thus the more noise that will result.

A handbook is not expected to have a theme, but in this respect this one is different - it does. It is to break the negative circle created by declining aural sensitivity and the inept operating concepts of those responsible (intentionally or not) for the design of the acoustic community. Our work is fundamentally one of design, in the sense that we are concerned as much with how things ought to be as with how they are. Leadership in this area is slow in coming from the scientific community and is virtually non-existent from the musical one, into whose care the cultivation of sound and meaning was placed some time ago. Our theme then must be experienced in terms of all the documents we have published2, and not simply this one, where it tends to lie below the surface.

During the preparation of this document, the style and nature of its format has often been debated. Should it be a dictionary, or a glossary or a handbook, and so on. In the end it has acquired characteristics of all three. Many entries attempt to be explanations rather than strict definitions, and we have not hesitated to add our own assessment and qualifiers where appropriate. We have also wanted the text to be a useful reference book where information from many sources could be collected for quick access, and so various charts, diagrams and lists have been included to serve this purpose. Terms used in the explanation of another term, and which are themselves defined elsewhere, appear in capitals in the text, at least where it is felt that the additional cross-reference will be necessary or helpful.

Although our aim has been to promote clarity without sacrificing accurate detail, there are many terms and concepts included which no few paragraphs could possibly elucidate to the novice in this field. In this sense, the document is not a textbook, since it is impossible to supply all the related technical background that would be required for an easy assimilation of certain concepts. Instead, we have treated the term as if it had been encountered in some context which prompted the reader to come here for further information. By using the type of vocabulary which normally surrounds the term where it most frequently occurs, we hope that useful insights into its nature will be gained.

Naturally, the terminology which the World Soundscape Project has contributed is included as well. It should be pointed out, however, that only a few of the necessary concepts required by soundscape studies have to date been formulated, but all of them differ from the traditional vocabulary by their positive approach, compared with the negative aspects of sound terminology that have already been mentioned.

For instance, we include the conventional term 'noise pollution', but because of its negative implication (the pejorative sense of 'noise') and its lack of parallel form to similar types of pollution (such as pollution of the air and water which can only be compared to pollution of the soundscape), we propose the alternative term 'sound pollution'. The reader will note from its explanation that we define it as an imbalance of a soundscape, not simply as 'too much loud noise'. To say it is an imbalance implies that it depends on how people perceive and understand the balance or lack of it, in other words, how each sound is weighted in its contribution to the whole. On this basis, loudness (which still is the fundamental emphasis of all noise measurement systems, no matter how modified they may be by other considerations) is not of primary importance. If a sound is understood by someone to be annoying or out-of-place, or to be crowding out other sounds, then this is sufficient to create an imbalanced soundscape. No such objective measurement can arrive at the same conclusion based on physical characteristics of the sound alone (unless one reverts to von Helmholtz's definition of noise as any aperiodic signal, by which 60 cycle hum, transistor radios and background music could never contribute to noise pollution).

The nature of the soundscape is that it joins the outer physical reality to the inner mental processes of understanding it; in fact it is the relationship between the two. No system that accounts for the former while ignoring the latter can be said to be adequate for soundscape analysis, and yet none of those responsible for the sonic engineering of society act on that insight. Such basic modes of perception as differentiation between foreground and background are at the basis of our terms 'sound signal' and 'keynote'. Without the ability to make such a simple distinction, how can one begin to discover how people organize the sounds around them into a representation of the soundscape? But this is the situation we are in, having to point out such simple matters to those who have forgotten how to listen.

A general word of caution to the reader: do not try to use this volume until you have started to listen. Nothing will make sense until you have begun to discover what sound is all about by the only means that is truly valid - listening and thinking about what you have heard. If you try to read about sound first, you will probably get lost in the jungle of terminology and forget your ears. Once you have heard what is going on around (and inside) you, once you have begun to perceive balance and imbalance in a soundscape, once you have discovered how sound creates contours of space and time, then perhaps in hopefully quiet moments you might venture into the thoughts of those whose language will require the reference material contained here. But beware, too much reading and talking about sound may threaten the security of your personal understanding. However, if you are to act within a society committed to talking about sound as opposed to understanding it, you will need the benefit of the technical terminology in order to challenge it when it is used misleadingly. If this is not possible for you, then close the book immediately and go back to listening - it will be of greater benefit.

Our work is incomplete - it may always be so. But for those who have assisted me in bringing this task to its present form, I have the greatest thanks. These are my colleagues, R. Murray Schafer, Peter Huse, Bruce Davis, Howard Broomfield, Hildegard Westerkamp and Adam Woog, who have contributed to the material and its editing; Wendy Pearce, John Oswald, Mike Grambo and A.J. Born who helped with the graphics and many other problems; Linda Clark and Judy Barker who have carefully typed and re-typed it, and Joyce Perry who did the typesetting. Special thanks go to Jean Reed, Dr. Leigh Palmer, Dept. of Physics, Simon Fraser University, Prof. J.B. Large, Institute of Sound and Vibration Research, University of Southampton, Mr. C.A.G.M. Tempelaars, Institute of Sonology, Utrecht, Prof. Allen Strange, San Jose State University, Prof. David Rosenboom, York University, Dr. Diana Deutsch, Centre for Human Information Processing, University of California at San Diego, and Dr. John Grey, Centre for Computer Research in Music and Acoustics, Stanford University, who have read the manuscript and offered valuable comments and suggestions.

Barry Truax,
Director of Research,
World Soundscape Project,
Department of Communication,
Simon Fraser University, Burnaby, B.C.

August 25, 1977


1. Fundamentals of Noise: Measurement, Rating Schemes and Standards, U.S. Environmental Protection Agency, Washington, D.C., Report NT1 D300.15, Dec. 1971, p. 120.

2. See handbook entry under WORLD SOUNDSCAPE PROJECT.