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INTRODUCTION: Sound is .... |
An interdisciplinary survey
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INTRODUCTION: Sound is .... |
To begin the Tutorial, it may be useful to get an overview of the basic approaches of some of the disciplines we will be presenting here. The main point is to introduce them in a general way to establish their basic perspectives and give some idea of how they approach the subject of sound. We also hope to show that there are important links, as well as contrasts, between the scientific, social and artistic traditions within which they have developed. When understood together, they can provide us with a better appreciation for the role that sound plays in our lives and the environment.
A) Sound is ... , an overview
B) How different disciplines approach sound
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A. Sound is .... , an overview. If we asked a lot of people what sound is, there would likely be many different perspectives, but a common theme would be about sound related to hearing. But from a communicational and soundscape perspective, we would want to place more emphasis on listening as our way of processing and understanding sound, not just registering it as a sensory phenomenon. Similarly, there are other issues involved if our focus is mainly “sound is something we can hear”, such as:
– our hearing range is limited in terms of frequency; in particular, in the lowest frequency range (below about 20 Hz) called infrasound, we are more likely to feel the vibration of sound waves, not actually hear it
– in the low frequency range above infrasound, called the “bass” in music, the sound waves will interact with our physical body, and resonate in the chest and other cavities; sound and hearing is more than what comes through the ear
– in the very high frequency range (above 20 kHz) called ultrasound, you probably know that other species, including cats and dogs, can hear sound waves that we cannot; unfortunately we will not be able to incorporate all bio-acoustic aspects of sound here, other than in some tantalizing references, such as the Acoustic Niche Hypothesis
– below that very high frequency range, hearing loss due to age and noise exposure can severely reduce our sensitivity to sound; this is something we will deal with in the Audiology module
– you can also experience sound that does not originate in the external world; hearing has a non-linear component called combination tones that we will explore; a ringing or other buzzing sensation can be experienced after noise exposure, and when persistent is an unfortunate indicator of more serious hearing problems
– the term “aural diversity” has been suggested in recent years to draw attention to the fact that one cannot assume “normal hearing” to be the actual norm, since there are so many variations in human hearing – and have been historically – that we cannot always know what people are hearing in terms of sound
Note: at this point, don’t worry if you don’t understand all of the technical terms being used here. They will be explained in the subsequent modules, and links to our reference work, the Handbook for Acoustic Ecology, will be provided.
Going beyond the above limitations to what our relationship to sound is, also consider the following:
– our concept and experience of sound cannot be separated from its complement, silence; each depends on the other, and its role has been widely discussed from a philosophical perspective through to an ecological one, a discussion that cannot be adequately dealt with in this Tutorial, although one important role is incorporated into the Speech module
– from a communicational perspective, we can and should think of sound as creating relationships within an ecoacoustic system, our communities, and our everyday lives, not merely as the transfer of energy and messages which has traditionally been the norm with models of sound
– our understanding of the role of the brain in sensory processing is still developing through research, but one principle to keep in mind is that the processing of auditory information is closely linked to all other brain centres; in this Tutorial, we need to treat sound largely in isolation from the other senses, but as we go through the psychoacoustics of sound perception, we will always get to the point where higher processing in brain functions will open up to much more complexity than we can deal with here
– concepts such as “beyond the ear” and Seth Kim-Cohen’s argument for a “non-cochlear music” (in his book In the Blink of an Ear) suggest an even broader approach to what the implications of sound are, so we need to keep an open mind on the subject
On the other hand, what we hope to achieve with this Tutorial is to bridge many of the disciplines that have contributed to our understanding of sound. As we will discuss next, they have evolved along their own paths and developed their own terminology, not always making links with each other.
Our approach is to assume that sound is an interdisciplinary area of study, and we will do our best not to be confined within any one approach.
In addition, as you can see in how the modules here are structured, we will provide an equal balance between the traditional acoustic models of sound, and the electroacoustic practices that have developed over the last century. The differences between them are fundamental, as we will see in the next module (that spans both areas), but electroacoustic practice is inherently related to, and dependent on, our experience of acoustic sound as it has developed over a much longer time. And, of course, electroacoustic practice culminates with acoustic sound.
Moreover, electroacoustic sound over the better part of the past century has profoundly changed from an analog to a digital practice, although we will show how digital practice is embedded within the analog. Like all innovation, it is the new affordances of the digital format that are the most striking, but we will always introduce them in relation to their analog predecessors.
Finally, this Tutorial is geared towards the creative aspects of sound and sound design, most clearly with examples of electroacoustic composition, and the biggest overlap with the acoustic world, namely Voice and Text-based composition, and Soundscape Composition. Despite their more experimental forms being cultural marginalized today, it is our belief that they have a great deal to contribute to an expansion of our experience of sound and listening.
B. How different disciplines approach sound. One of the many problems with pursuing an interdisciplinary approach is that the most established, traditional disciplines have developed their own conceptual framework and “correct” terminology to describe what they are studying. If you do not “speak their language”, in the sense of using that terminology correctly, you will not be taken seriously.
However, when those who are “outside” the discipline come to visit and learn from its professional practitioners, their curiosity is often not satisfied because of the lack of access to the most relevant information. This is not really the fault of the discipline, because research publications are the primary form of communication between researchers, and there is little need for explaining matters in simpler language to outsiders.
That is left to projects referred to as “knowledge transfer” (which is also the intent of this Tutorial), and often the practitioners themselves, with notable exceptions, are not the best equipped to handle that.
We are going to introduce the main academic disciplines that are essential to an understanding of sound by a somewhat novel approach (which dates back to the first edition of the Handbook in 1978), in the form of a simple chart. In it we try to identify the basic “unit” and “ground” of the discipline, and suggest what its approach to “design” will be.
The terms “figure” and “ground” are from Gestalt psychology and geared towards perception, but we will apply them in a more general sense to this survey. We will substitute “unit” for “figure” and treat it as the most basic concept used in a discipline from which all else will be derived. The analogy is not perfect, but it will attempt to capture the general model of sound which is inherent to the discipline.
The concept of “ground” is simply the logical complement to the unit, i.e., that which it is not, or that which it is distinguished from. With the exception of soundscape studies, the basic model in each of these disciplines is the energy and signal transfer model that will be discussed in the next module.
DISCIPLINE
UNIT
GROUND
DESIGN
ACOUSTICS (theoretical)
sound wave
oscillation
medium
applied acoustics
ACOUSTICS (applied)
sound wave
noise
atmospheric pressure
ambience
acoustical engineering
noise control
architectural acoustics
PSYCHOACOUSTICS
stimulus
(sound object)
background noise
(silence)
acoustic design
auditory display
ELECTROACOUSTICS
audio signal
background noise
sound synthesis
audio design
MUSIC (Western)
note
silence
composition
SOUNDSCAPE STUDIES
sound event
sonic environment
keynote
ambience
soundscape design
acoustic ecology
Acoustics. The discipline of “pure” or theoretical acoustics is a branch of Physics, and it generally deals with mathematical models of sound and its behaviour. The sense of it being “pure” is that it generalizes the behaviour of sound as an oscillation and a wave, characteristics of oscillatory motion in general that are common to all forms of energy transfer, including for instance, electromagnetic radiation such as light waves or radio waves.
This generalization is also reflected in the “ground” being a “medium”, so it is not specific to air, liquid, or solid. Sound being a physical vibration needs this medium to propagate, and therefore is restricted to the planet as a whole, not outer space.
The design aspect of acoustics is usually left to acoustical engineers, as in the next category, but there are instances where a theoretical acoustic construct, such as destructive interference, for instance, finds a practical application as in noise-cancelling headphones.
If you look at the subject index of the Journal of the Acoustical Society of America (JASA), you will find thousands of subtopics, not all of which refer to sound that can be actually heard.
Applied Acoustics. As mentioned, the applied aspect of acoustics is Acoustical Engineering, a branch of Engineering in general, that deals with real-world issues involving sound. Their conceptual unit is also the sound wave, but since a large part of acoustical engineering deals with “noise”, that is equally a fundamental unit.
The traditional approach to acoustic engineering is quantitative, measuring every aspect of the sound wave in actual environmental conditions. Hence the “ground” is equally applied. A sound wave is considered to be a coherent variation in sound pressure around the local atmospheric pressure (which changes with altitude). The term “coherent” refers to the orderly movement of air particles around the random movement of the molecules of air, a liquid or a solid.
Therefore, what constitutes measurable noise as a "unit" needs to be distinguished from ambient noise which is always present, clearly a fairly arbitrary distinction for a continuum, but one that can be done statistically. For instance, an ambient sound level is regarded as the one that is exceeded 90% of the time, as we will discuss in the Noise Measurement module.
Acoustical engineering often extends into the matter of subjective response, but it is done with the same attempt at objectivity, not subjectivity. This is made possible by the prevailing Stimulus/Response (S/R) model which allows a subjective response to be measured. In other words, these engineers are not trained in Psychology and Sociology and would prefer to leave such considerations to those who are. The other solution is to limit subjectivity to general terms like “annoyance”.
However, over the past decade or so, particularly in Europe, acoustical engineers have accepted that a way forward in dealing with noise issues is to adopt a soundscape model, that is, to include the sonic environment as it is perceived. This involves qualitative research, and so it would appear that a new generation of acoustical engineers will need to broaden their training.
Of course, it also needs to be acknowledged that the branch of acoustical engineering known as architectural acoustics has been practiced much longer for dealing, most famously, with concert hall acoustics. Subjectivity in that case has come to be measurable through listening tests, and in the classical S/R model, correlating them with physical variables.
Psychoacoustics. In the next module, we will trace the rise of psychophysics in the 19th century as a branch of Psychology. Psychophysics applies to all forms of sensation, and so Psychoacoustics devotes itself to its auditory forms. Its traditions are also rooted in the classic S/R model, that became quantifiable in the 1920s with the emergence of the electrical form of the audio signal that could be used for testing human response, including hearing ability. The key unit, then, is the “stimulus” which needs to be isolated from both the “background noise” (e.g. via headphones or an isolation chamber), and any other sounds that might be present and confound the human response.
All of our Acoustic modules will take you through the classical approaches of Psychoacoustics and what they tell us about sound and how it is processed in hearing. We will also cover how the classical model has evolved into the more contemporary unit of the “percept” as an integrated perceptual image, involving cognitive behaviour. These distinctions should make it clear why the "psychological effects of sound and music" are not really found in Psychoacoustics, but more likely in Psychology and Sociology, at least not until more recently.
The two terms in brackets in this category (sound object and silence) refer to an alternative form of psychoacoustics that emerged in the 1950s with the musique concrète work in Paris developed by composers such as Pierre Schaeffer at the GRM, a radio sponsored studio. Their “stimulus” unit was called a “sound object” (l’objet sonore) which could be isolated in a studio recording by close miking.
In the second Vibration module, we’ll include some excerpts of their Solfège de l’objet sonore publication (1967) where the electroacoustic manipulation of recorded sounds led to an awareness of the complexity of real-world sound and timbres that ran opposite to the reductionistic models of Psychoacoustics at the time.
Except for those electroacoustic composers who of course developed compositional strategies from their sound object research, design applications of psychoacoustics have been carried out more pragmatically with a range of techniques we can call “acoustic design”. Perhaps the first was the very practical one of telephone bandwidth being limited to the essential speech frequencies in order to maximize the efficiency (and profitability) of telephone networks in the 1930s.
However, as documented by Jonathan Sterne in his book on the subject, the contemporary mp3 encoding methodology for data reduction in music transmission is guided by psychoacoustic principles as well. At a different level of industrial design, background music (popularly branded as Muzak) was added to factory and other working environments, particularly during the war years, to promote productivity, and later in consumer contexts, based on psychoacoustic principles of stimulation. In recent decades, the practice of mapping any form of data onto sound, called sonification, sometimes based on psychoacoustic principles, has supported the development of auditory display systems.
Electroacoustics. In the next module, we will outline the historical development of electroacoustics in the context of recording, radio and telephone, all made possible by converting acoustic energy to an audio signal which is unconstrained by the limits of acoustic behaviour. Therefore, the audio signal is the obvious unit, and in the analog tradition it needed to be distinguished as clearly as possible from the inevitable background noise, which was its “ground”.
Since this dramatically new form of sonic communication was tied to an emerging commercial industry, its technical developments had to run in parallel with the creation of the consumer, and so we will also deal with advertising strategies in the 20th century that promoted the concepts of “fidelity” and “sound quality” in making purchasing decisions.
What is not as well understood is that these technological and economic developments allowed not just new technology but new forms of listening to develop, both the more analytical type of foreground listening, and the more distracted background listening as reproduced sound became used as an accompaniment soundscape. We will document both of those developments, and of course the Electroacoustic modules are precisely formulated to develop analytical listening abilities as well as creative output through sound synthesis and audio design.
Music. The development of music in Western culture over the centuries also interacted with the communication modes of its time, which up until the 20th century, were formulated within the literate tradition of reading and writing. The tradition of reading and writing a score is based on the “unit” of music being the note – a self-contained musical event with pitch, loudness and duration – that could be indicated in a graphic form that evolved from the mnemonic style of notation in Medieval times.
The assumed “ground” for the musical note is an imagined silence, one that can also be quantified in notation (with its only variable, duration). Calling it “imagined” reflects the kind of idealization of music as a self-contained entity, and some of the more attentive listening practices that evolved in the later 19th century through the social structure of the concert hall which gradually established audiences as silent listeners.
However, this socially established figure-ground could be challenged. John Cage, in his well-known 4’33” work flipped figure and ground by notating no sounds in the score and letting the ambience provide the foreground, thereby challenging listeners not to bracket out those sounds. Somewhat similarly, but for different purposes, R. Murray Schafer in one of his educational booklets added notations of sounds actually heard during a performance of a Beethoven Symphony, to the score.
This approach to music in notated form contrasts with purely aural traditions that never disappeared (just as written language didn’t supplant oral traditions). However, the older aural/oral traditions are ones that are embedded in their cultures, so it’s doubtful we could apply a unit/ground concept in those contexts. Admittedly the “ground” could be the culture itself, but it is obviously not in any kind of opposition to the music being practiced.
Composition, in the Western literate tradition, continues to be bound to the written score, but just as electroacoustic technology changed listeners’ relationships to sound, so too it has redefined electroacoustic music as more sound based than note based. However, it is our belief that, despite being culturally marginalized, experimental electroacoustic composition offers the greatest advancement to creativity through sound.
My favourite anecdote about how disciplinary traditions can collide occurred during the first joint meeting of the Noise and Music sections of the Acoustical Society of America Conference at a hotel in Washington, DC. Several other colleagues and I were presenting examples of soundscape projects to the music group, and I was playing a recording of Vancouver foghorns as an example of a soundmark. A fellow in the session next door popped his head in, and (rather sheepishly) requested we turn down the sound as it was “disturbing the equations”.
Soundscape Studies. It could be argued that, like oral traditions, soundscape studies does not have a clearly defined unit/ground basis, because it treats the soundscape as a whole. However, in contrast to the “sound object”, isolated from its context, the equivalent in soundscape studies would be the “sound event” that attracts foreground attention, or the sonic environment perceived as a whole. In fact, the World Soundscape Project’s recordings provide support for that designation as they always documented their sounds in context, unlike a sound effects library, for instance, that isolates them.
The “ground”, then, would be the keynote sound which is defined as any sound that stays consistently in the background of the listener’s perception because of its ubiquitous presence. Sometimes this is the ambience, but it can also be a sound signal that is frequent and non-salient in the sense that it doesn’t involve the listener. An example would be living near a busy hospital, where ambulance sirens are commonplace.
In terms of soundscape design, we will be presenting its various elements in terms of acoustic space, understanding how it functions and when it achieves a functional balance. From a larger perspective, we can try to understand the soundscape as a system of interacting elements that seems best described as an acoustic ecosystem.
First, however, we need to start from the beginning in the next modules to establish a foundation of knowledge about how sound functions, how it is analyzed in the auditory system, and how it leads to the kind of information that listening provides. To do this, we will examine the energy transfer model in each discipline to understand how that process begins.
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