Fundamentals of Sound - Module 01: Introduction

Fundamentals of Sound: definitions and scope of study

DEFINITIONS

The study of sound is a multidisciplinary field concerned with the physical (e.g., vibrations; waves), physiological (e.g., structure and function of the ear), and perceptual (e.g., auditory sensations) correlates of sound production, transmission, processing, storage, reproduction, and reception. This course forges a link among three frames of reference --physical, physiological, and perceptual-- by examining how physical sonic stimuli interact with the auditory system to give rise to auditory sensations and perceptions.
["Frame of reference": A collection of concepts and definitions accepted by a particular field or domain of discourse, representing a particular way of understanding the world.]

Cognitive Psychology of Sound extends this general framework by examining the implicit and explicit processes through which auditory perceptions are organized into meaningful wholes. It provides an empirical basis for understanding how we interpret and evaluate sound and sound structures, to be addressed in greater detail elsewhere in the curriculum.

For an alternative introductory resource relevant to our course, see Music & Science [ Center for Music & Science; University of Cambridge ]

FIELDS OF STUDY

Our study of sound will engage several fields of acoustics and related disciplines:

Physical Acoustics (vibrational/physical frame of reference)
The study of the generation, transmission and modification of sound waves.

What are the physical bases of our meaningful and emotional responses to sound?
Specifically:
    _ How are sound waves produced, and how are they influenced by the source's material, construction, and mode of excitation?
    _ How does transmission through the air and other media modify sound waves before they reach our ears?

Of the many relevant areas, we will focus on Musical, Architectural, and Environmental Acoustics.

Physiological Acoustics (biological/physiological frame of reference)
The study of the auditory system's response to sound waves.

What are the physiological bases of our meaningful and emotional responses to sound?
Specifically:
    _ How does the ear process acoustic energy, and at what degree of accuracy?
    _ How is acoustic energy transformed into neural activity and auditory sensation?

Together, Physical and Physiological Acoustics provide the foundation for Psychoacoustics, a discipline that investigates the relationship between the physical properties of sound stimuli and auditory sensations and perceptions.

Signal Processing and Notation (symbolic frame of reference)
The study of sound through its electronic, graphical, and mathematical representations
(a special application of semiotics --the study of signs and symbolic systems-- of which music notation is an example).

What are the formal bases of our meaningful and emotional responses to sound?
Specifically:
   _ How does manipulating a sound's electronic or symbolic representations relate to manipulating the acoustic wave and the resulting auditory sensation, and vice versa?

In our course, we will limit our investigation to a small subset of graphical representations of sound, particularly sound signals & spectra, along with a conceptual introduction to the fundamentals of digital audio.

COURSE FOCUS: Auditory Sensitivity and Perception

In our study of sound we will explore

Absolute Thresholds (limits of sensation):
    The lowest or highest stimulus magnitudes that are safely and reliably detected as sensations.

Difference Thresholds (Just Noticeable Difference or JND):
    The minimum change in a physical variable required to produce a detectable change in the corresponding sensation.

Nature of Relationship between Physical and Perceptual Changes:
    Direct versus inverse relationship; linear versus nonlinear relationships and type of nonlinearity.

Effects of Stimulus Duration and Level on items 1-3:
    Impact of the degree of exposure to a stimulus on perception, including phenomena such as adaptation, fatigue, and damage.

Effects of Stimulus Interactions and Broader Context on items 1-4:
    Impact of the presence of additional stimuli --whether simultaneous, preceding, subsequent, or remembered, and in any modality-- on stimulus perception and its relationship
    to the corresponding sound wave's physical features.

2. NOISE The meaning of noise varies with context and frame of reference, particularly between physics and communication. Although noise falls within the broader categories of sound and signal, it is often contrasted with them, by referring to unintended, undesirable, or unfamiliar sounds/signals. The concept of noise is further ambiguated by Noise Music, which challenges conventional distinctions between sound, noise, and music (see below).
Noise as "Unwanted Sound" Noise Music
For this course, we will distinguish between two definitions of noise, depending on context.
*2.1. Noise as a Physical Phenomenon* Noise is an auditory sensation associated with non-periodic sound signals with broad, dense, relatively flat spectral distributions. (Physical frame of reference: characteristics that can be objectively measured)	*2.2. Noise as Unwanted Sound* Noise is an auditory sensation that is undesirable, unpleasant, or unintended within a given context, interfering with sounds or auditory experiences that are desirable, pleasant, or intended within the same context (Cognitive/semantic frame of reference: judgments that depend on communication, context, and subjective evaluation)
	(image source)
We will alternate between these two definitions, as appropriate to the context.

David Byrne (2012)) (short video interviews) Book Review (The Guardian) AUDIO BOOK: Part 1 Part 2	Jeff Tweedy (2020) (podcast hosted by Malcolm Gladwell)	3. MUSIC For the purposes of this course, we adopt the following operational definition: Music is temporally organized sound and silence that is a-referentially communicative within a context. [ Kendall, R. A., & Carterette, E. C. (1996). Comparative music perception and cognition. In D. Deutsch (Ed.), The Psychology of Music (2nd ed., pp. 311–345). Academic Press. ] The definition emphasizes two central aspects of music: temporal organization & communication. Music is an essentially temporal and emotional art. Susanne Langer describes music in terms of virtual time, while Bennett Reimer argues that music's core value lies in its ability to articulate the human emotional dimension, serving as a unique form of "knowing through feeling". When listening to music, we respond in some way; our behavior, attention, or experience changes, indicating that we received, interpreted, or participated in the creation of something. What we receive is not necessarily a specific verbal message. It is an intention communicated through the patterns and relationships emerging in the act of organizing sound in time. The result is comparable to the communication effect of the prosodic dimension of language --its rhythms, intonation, and patterns of emphasis. The importance of context is a direct consequence of music as communication. All communication involves both shared and unshared knowledge; together, these form the broader context within which communication takes place. Music's potential for a-referential communication --communication that does not necessarily refer to anything outside the auditory sensations themselves-- distinguishes it from ordinary linguistic communication. Analogous to abstract animation, music can communicate through patterns of motion, change, action, and development, without necessarily representing specific objects or events. In this sense, music may be understood as a kind of noun-less language, composed primarily of "verbs" and actualized in the temporal unfolding of sonic processes and relationships (potential / motion / action / narrative: all concepts with a fundamentally temporal dimension).
Model of musical communication - adapted from Kendall & Carterette,1990: 132.		4. MUSIC AND COMMUNICATION Understanding music involves interpretive translation across frames of reference, with music emerging through interactions, at various levels, among composer, performer, and listener, broadly defined. Like other forms of communication, music depends on some degree of shared explicit (i.e. describable) and implicit (i.e. unspoken/assumed) knowledge. This shared knowledge helps make the meanings we infer during a musical experience relatively consistent and intelligible. However, intended and received messages are not necessarily the same. This is especially true of music, given its a-referential (or self-referential) potential. In addition, although some shared knowledge is necessary for effective communication, each communicative encounter always involves some degree of unshared knowledge. This helps explain why there is no one-to-one correspondence between a composer's intended message and the message constructed by a listener. The term constructed message is important: Listeners are not passive recipients of musical information. They actively organize and interpret what they hear. 4.1. Listening as an Act of Configuration Listening to music means configuring music. Listening involves organizing incoming sounds into patterns, relationships, and temporal wholes that are meaningful to the listener. Listeners naturally seek patterns and may discover or even configure relationships that were not intended during composition. This can occur even in the extreme case where no patterns were intended, as in some aleatoric compositions or when listening to environmental sounds. The productive potential for discovering new organizations and meanings allows musical works to outlive their composers, historical eras, styles, intensions, and original cultural contexts. Sounds and sound patterns, by themselves, do not necessarily constitute music. The listener is the agent through whom sounds and their combinations are transformed into music and art. A composer can be considered the first listener of a work; from the standpoint of music perception, this may be where their privileged status ends.
THE WORLD OF MUSIC Sampling the depth and breadth of sonic and structural possibilities that can constitute music. Additional resources: Music across the world & The evolutionary bases of music (University of Cambridge) The Music Instinct: Science & Song (PBS)
Excerpt from 'Raga Hameer'. Traditional piece arranged by Vilayat Khan. 'The Music of India and Pakistan' CD. The Rough Guide. World Music Network © 1995. 'Green Frog'. Arnhem Land; Northern Australia, Wangga song. A.Maralung: voice & clapsticks; P.Manaberu: didjeridu. 'The Garland Encyclopedia of World Music CD, Vol. 9: Australia & the Pacific Islands.' Garland Publishing © 1986. 'Caymmi Mostra Ao Mundo O Que A Bahia E Mangueira Tem'. Rio De Janeiro. Samba Enredo by Thobias Da Vai-Vai. 'The Music of Brazil' CD. The Rough Guide. World Music Network © 1998. 'Almamy Bocoum'. Senegal; West Africa. By Mansour Seck. 'West African Music' CD. The Rough Guide. World Music Network © 1995. 'Mauritania My Beloved Country'. Mauritania; West Africa. By Khalifa Ould Eide & Dimi Mint Abba. 'West African Music' CD. The Rough Guide. World Music Network © 1995. 'Jaya Semara'. Indonesian Gamelan for Kebyar gong. UCLA Gamelan Ensemble. Three-part Bulgarian vocal piece. Fieldwork recording by Prof. T.Rice, UCLA. 'Jesu, Joy of Man's Desiring', from the Cantata 'Herz und Mund und Tat und Leben.' J.S.Bach (BWV 147). W.Basch: Trumpet; W.Rubsam: Organ. CD, Pro-Arte Records © 1986. 'Sonata No. 2 for Cello and Piano (1994) - II: Allegro', in "Schnittke - Complete Works for Cello and Piano - Alexander Ivashkin, cello - Irina Schnittke, piano" - Chandos Records Ltd. © 1998. Excerpt from 'Symphony No. 21 - Opening' by Anton Webern (1927-1928).

Sound, Noise, Music: Essential and Operational Definitions
ESSENTIAL AND OPERATIONAL DEFINITIONS *Essential definition: a definition that, within a given context: (a) identifies the necessary* (i.e., without them the concept would lose its identity) and sufficient (i.e., no additional ones are required) characteristics of a concept, and (b) uniquely distinguishes the concept from all others (i.e., no other concept shares exactly the same defining characteristics). Operational definition: an essential definition of a concept that also (a) identifies procedures or operations (numerical or otherwise) that allow its instances to be reliably identified and measured, within a given context, and (b) permit other investigators to repeat the procedure and compare results. In short: Essential definitions establish what we mean; operational definitions establish how we determine whether, and to what extent, the definition applies in a particular case. Example 1: Psychoacoustics — Absolute Hearing Thresholds Essential definition: The lowest and highest sound stimulus magnitudes that are safely and reliably detected as auditory sensations. Necessary and sufficient characteristics: i) a sound stimulus and ii) general detection criteria and listening conditions. Definition uniqueness: it distinguishes an absolute threshold (detection of a stimulus) from a difference threshold (minimum detectable stimulus change). Operational definition: Specific stimulus type, listening conditions, testing procedure, detection criterion, and numerical outcome. For example: Present a listener with a tone of a specified frequency and duration, varying its sound pressure level in a controlled listening environment. Use a standardized procedure, such as repeated trials with an adaptive staircase, to estimate the level at which the listener detects the tone according to a predetermined criterion (e.g., 50% detection). Express the resulting threshold in dB SPL, under the specified test conditions. Example 2: Geometry — A Triangle Essential (and operational) definition: A triangle is a closed, plane geometric figure formed by three straight line segments joined end to end. Necessary and sufficient characteristics: i) closed, planar figure with ii) exactly three straight sides, joined end to end. Removing any of these characteristics would allow figures that are not triangles, while features, such as particular lengths or angles, do not add to the concept. Definition uniqueness: This definition distinguishes a triangle from other plane polygons, such as quadrilaterals (four sides) and pentagons (five sides). Note: The triangle example is especially straightforward because its essential definition necessarily contains characteristics that are precise and readily verifiable. The psychoacoustic example illustrates why definitions in empirical sciences require a specific "operational" component.
	1. SOUND The term "sound" is often used loosely to refer to three distinct phenomena, each associated with a different frame of reference: (a) Auditory sensation; the experience of hearing (perceptual frame of reference) (b) Physical disturbance; a disturbance in a medium that can produce an auditory sensation (physical frame of reference) or (c) Intended/desired/pleasant auditory sensation; often contrasted with noise, understood as unintended/undesired/unpleasant auditory sensation (cognitive/semantic frame of reference) For this course, we adopt the following definition: Sound is the sensation arising when sonic energy —vibrational energy within the response limits of the human auditory system— reaches the ear. Review the 3 video examples of sonic energy visualization.