TORIma Academy Logo TORIma Academy
Acoustics
Arts

Acoustics

TORIma Academy — Branch Of Science

Acoustics

Acoustics

Acoustics is a branch of continuum mechanics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration,…

Acoustics is a branch of continuum mechanics that focuses on mechanical wave phenomena in gases, liquids, and solids, encompassing topics such as vibration, sound, ultrasound, and infrasound. Professionals specializing in acoustics are termed acousticians, whereas those engaged in acoustical technology are often referred to as acoustical engineers. Acoustics finds widespread application across nearly all facets of contemporary society, notably within the audio and noise control sectors.

Audition constitutes a vital survival mechanism in the animal kingdom, while speech represents a hallmark of human cultural and developmental evolution. Consequently, the discipline of acoustics permeates numerous aspects of human civilization, including music, medicine, architecture, industrial manufacturing, and military applications. Similarly, various animal species, such as songbirds and frogs, employ sound and hearing as fundamental components of mating rituals or territorial demarcation. As observed in numerous other domains of knowledge, the interplay among art, craft, science, and technology has collectively propelled advancements in acoustics. Robert Bruce Lindsay's "Wheel of Acoustics" provides a widely recognized conceptual framework illustrating the diverse subfields within acoustics.

History

Etymology

The term "acoustic" originates from the Greek word ἀκουστικός (akoustikós), signifying "pertaining to hearing" or "prepared to hear," and from ἀκουστός (akoustós), meaning "heard" or "audible." Both terms ultimately stem from the verb ἀκούω (akoúō), which translates to "to hear."

The Latin equivalent is "sonic," from which the term sonics historically served as a synonym for acoustics before evolving into a distinct subfield. Frequencies exceeding the audible spectrum are designated "ultrasonic," while those below it are termed "infrasonic."

Early research in acoustics

During the 6th century BC, the ancient Greek philosopher Pythagoras investigated the aesthetic qualities of musical sound combinations, discovering explanations rooted in numerical ratios that characterize the harmonic overtone series of vibrating strings. He is credited with observing that harmonious tones result when the lengths of vibrating strings are represented by integer ratios (e.g., 2:3, 3:4), with smaller integers correlating to greater harmony. For instance, a string of a given length would produce a notably harmonious sound when paired with a string twice its length, assuming other variables remain constant. In contemporary terminology, if a plucked string produces the note C, a string of double its length will yield a C an octave lower. Within a specific musical tuning system, the intermediate tones are subsequently defined by ratios: 16:9 for D, 8:5 for E, 3:2 for F, 4:3 for G, 6:5 for A, and 16:15 for B, arranged in ascending pitch.

Aristotle (384–322 BC) posited that sound comprised compressions and rarefactions of air, describing it as "falling upon and striking the air which is next to it," an insightful articulation of wave motion's fundamental character. The treatise On Things Heard, commonly attributed to Strato of Lampsacus, asserts a correlation between pitch, the frequency of air vibrations, and the velocity of sound.

Circa 20 BC, the Roman architect and engineer Vitruvius authored a treatise detailing the acoustic characteristics of theaters, encompassing discussions of interference, echoes, and reverberation, thereby laying the groundwork for architectural acoustics. Within Book V of his work, De architectura (The Ten Books of Architecture), Vitruvius conceptualizes sound as a three-dimensional wave analogous to a water wave, which, upon encountering obstructions, would reflect and disrupt subsequent waves. He posited that the tiered seating in ancient theaters was intended to mitigate sound degradation and further suggested the strategic placement of bronze vessels (echea) of suitable dimensions within theaters to resonate with specific harmonic intervals—the fourth, fifth, and progressively up to the double octave—thereby enhancing desirable, harmonious tones.

During the Islamic Golden Age, Abū Rayhān al-Bīrūnī (973–1048) is credited with hypothesizing that the velocity of sound significantly lagged behind that of light.

The comprehension of acoustical phenomena progressed significantly during and after the Scientific Revolution. Galileo Galilei (1564–1642) and, independently, Marin Mersenne (1588–1648) elucidated the comprehensive principles governing vibrating strings, building upon the foundational work initiated by Pythagoras and his followers two millennia prior. Galileo famously stated, "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound," a profound assertion that foreshadowed the emergence of physiological and psychological acoustics. Between 1630 and 1680, numerous researchers, notably Mersenne, successfully conducted empirical measurements of sound velocity in air. Athanasius Kircher, a Jesuit scholar based in Rome, commenced acoustical investigations, drawing inspiration from Mersenne's 1634 publication, Harmonie universelle (Universal Harmony). Kircher subsequently authored two seminal works on acoustics: Musurgia universalis (Universal Music-Making) in 1650 and Phonurgia nova (New Sound-Making) in 1673. Concurrently, Isaac Newton (1642–1727) established the formula for wave velocity in solids, a foundational element of physical acoustics, documented in his 1687 work, Principia.

Acoustics from the Enlightenment Onward

The eighteenth century witnessed significant advancements in acoustics, underpinned by more robust mathematical and physical frameworks, attributed to the contributions of Euler (1707–1783), Lagrange (1736–1813), and d'Alembert (1717–1783). This period also saw the formal mathematical structuring of continuum physics, or field theory. The wave equation, notably, materialized across various domains, encompassing the transmission of sound through air.

During the nineteenth century, prominent figures in mathematical acoustics included Hermann von Helmholtz in Germany, who solidified the discipline of physiological acoustics, and Lord Rayleigh in England, whose monumental 1877 work, The Theory of Sound, integrated existing knowledge with his extensive original contributions. Concurrently, Wheatstone, Ohm, and Henry established the conceptual analogy between electrical and acoustical phenomena.

The twentieth century witnessed a rapid expansion of technological applications, leveraging the substantial scientific knowledge base that had been established. This expansion began with Sabine's pioneering efforts in architectural acoustics, followed by numerous subsequent developments. During the First World War, underwater acoustics proved instrumental in submarine detection. Sound recording and telephony significantly contributed to a worldwide societal transformation. The integration of electronics and computing elevated sound measurement and analysis to unprecedented levels of precision and complexity. The utilization of the ultrasonic frequency range facilitated entirely novel applications across medical and industrial sectors. Furthermore, innovative transducers, functioning as generators and receivers of acoustic energy, were conceived and deployed.

Defining Acoustics

According to ANSI/ASA S1.1-2013, acoustics is formally defined as: "(a) Science of sound, including its production, transmission, and effects, including biological and psychological effects. (b) Those qualities of a room that, together, determine its character with respect to auditory effects."

The discipline of acoustics primarily investigates the generation, propagation, and reception of mechanical waves and vibrations.

The stages illustrated in the diagram are fundamental to any acoustical event or process. These processes originate from diverse causes, encompassing both natural occurrences and volitional actions. Numerous transduction mechanisms exist, converting energy from various forms into sonic energy, thereby generating a sound wave. While a singular fundamental equation, the acoustic wave equation, governs sound wave propagation, the resulting phenomena are diverse and frequently intricate. This wave transmits energy across the propagating medium. Ultimately, this energy undergoes further transduction into alternative forms, which can be either naturally occurring or deliberately engineered. The ultimate impact can be exclusively physical or extend significantly into biological or volitional realms. These five fundamental stages are consistently observable across disparate scenarios, such as an earthquake, a submarine employing sonar for adversary detection, or a musical ensemble performing at a rock concert.

The fundamental aspect of acoustical processes involves wave propagation, a subject within physical acoustics. In fluid mediums, sound primarily disseminates as a pressure wave. Conversely, within solid materials, mechanical waves manifest in various forms, such as longitudinal, transverse, and surface waves.

Acoustics primarily investigates the pressure levels and frequencies inherent in sound waves, alongside their interactions with the surrounding environment. These interactions are characterized by phenomena such as diffraction, interference, reflection, or a combination thereof. The presence of multiple media can additionally lead to refraction. Furthermore, transduction processes hold significant importance within the field of acoustics.

Core Principles

Wave Propagation: Pressure Dynamics

Within fluid mediums like air and water, sound waves manifest as perturbations in the ambient pressure. Although typically minor, these disturbances remain perceptible to human auditory perception. The minimum sound intensity detectable by an individual, termed the threshold of hearing, is nine orders of magnitude less than the surrounding atmospheric pressure. The perceived intensity of these disturbances correlates with the sound pressure level (SPL), which is quantified logarithmically in decibels.

Wave Propagation: Frequency Characteristics

Physicists and acoustic engineers frequently analyze sound pressure levels by their frequencies, largely due to the human ear's interpretive mechanism. Perceptions of "higher pitched" or "lower pitched" sounds correspond to pressure vibrations exhibiting a greater or lesser number of cycles per second, respectively. A prevalent method in acoustic measurement involves sampling acoustic signals over time, subsequently presenting them in more informative formats like octave bands or time-frequency plots. Both of these widely adopted techniques facilitate the analysis of sound and enhance comprehension of acoustic phenomena.

The complete acoustic spectrum is categorized into three distinct segments: audio, ultrasonic, and infrasonic. The audio range, spanning from 20 Hz to 20,000 Hz, is significant because its frequencies are within the detectable limits of human hearing, finding applications in areas such as speech communication and music. The ultrasonic range encompasses very high frequencies, specifically 20,000 Hz and above. Its shorter wavelengths enable superior resolution in imaging technologies, making it crucial for medical applications like ultrasonography and elastography. Conversely, the infrasonic range represents the lowest frequencies, which are utilized for investigating geological events such as earthquakes.

Analytical instruments, including spectrum analyzers, enable the visualization and quantification of acoustic signals and their inherent characteristics. The spectrogram generated by these devices provides a graphical representation of the time-varying pressure level and frequency profiles that collectively define a particular acoustic signal.

Acoustic Transduction

A transducer functions as a mechanism for transforming one energy form into another. Within an electroacoustic framework, this specifically entails the conversion of acoustic energy into electrical energy, or vice versa. Examples of electroacoustic transducers comprise loudspeakers, microphones, particle velocity sensors, hydrophones, and sonar projectors. These instruments facilitate the conversion of sound waves to or from an electrical signal. The predominant principles governing transduction are electromagnetism, electrostatics, and piezoelectricity.

Transducers found in most conventional loudspeakers, such as woofers and tweeters, operate as electromagnetic devices. They generate acoustic waves by means of a suspended diaphragm actuated by an electromagnetic voice coil, which propagates pressure waves. Electret and condenser microphones, conversely, utilize electrostatic principles; when a sound wave impacts the microphone's diaphragm, its movement induces a voltage alteration. Medical ultrasonography systems incorporate piezoelectric transducers, which are fabricated from specialized ceramics where mechanical vibrations and electrical fields are intrinsically coupled by the material's inherent properties.

The Acoustician

An acoustician is defined as a specialist proficient in the scientific study of sound.

Educational Background

Acousticians encompass diverse specializations, typically holding a bachelor's degree or a more advanced qualification. While some pursue degrees specifically in acoustics, others enter the field through related disciplines such as physics or engineering. Proficiency in mathematics and scientific principles is often requisite for many roles within acoustics. A significant number of acoustic scientists are engaged in research and development activities. Some focus on fundamental research, expanding understanding of the perception of speech, music, and noise, encompassing areas like hearing, psychoacoustics, and neurophysiology. Conversely, other acoustic scientists investigate the propagation and environmental effects of sound, including underwater acoustics, architectural acoustics, and structural acoustics. Additional specializations are detailed within the subdisciplines section. Acoustic scientists are employed across various sectors, including governmental agencies, academic institutions, and private industrial laboratories. Many transition into careers in Acoustical Engineering. Certain roles, particularly academic faculty positions, necessitate a Doctor of Philosophy degree.

Subdisciplines

Archaeoacoustics

Archaeoacoustics, or the archaeology of sound, offers a unique sensory pathway to engage with historical environments beyond visual perception. This field involves the empirical investigation of acoustic characteristics within prehistoric sites, such as caves. For instance, sound archaeologist Iegor Rezkinoff examines the acoustic attributes of caves by employing natural vocalizations, including humming and whistling. Archaeological theories concerning acoustics often posit ritualistic functions and potential applications for echolocation within cave systems. Within archaeological contexts, a direct correlation exists between acoustic phenomena and ritual practices, where particular sounds were believed to facilitate spiritual experiences for participants. Furthermore, analogies can be drawn between the dynamic nature of cave wall paintings and the acoustic properties inherent to these subterranean environments. Given its relatively recent emergence as an archaeological discipline, the acoustic characteristics of prehistoric sites continue to be actively investigated.

Aeroacoustics

Aeroacoustics is dedicated to the investigation of noise originating from air movement, such as turbulence, and the propagation of sound through fluid air. This field of knowledge found early application in the 1920s and 1930s for aircraft detection prior to the advent of radar, and it is currently utilized in acoustical engineering to develop methods for aircraft noise reduction. Moreover, aeroacoustics provides crucial insights into the operational principles of wind musical instruments.

Acoustic signal processing

Acoustic signal processing involves the electronic manipulation of acoustic signals. Its applications encompass active noise control, the design of hearing aids and cochlear implants, echo cancellation, music information retrieval, and perceptual coding, exemplified by formats such as MP3 or Opus.

Architectural acoustics

Architectural acoustics, also referred to as building acoustics, is the scientific discipline focused on optimizing sound quality within indoor environments. This field typically encompasses the investigation of speech intelligibility, speech privacy, musical acoustics, and vibration attenuation within constructed spaces. Frequently examined environments include hospitals, educational facilities, residential buildings, performance halls, and recording or broadcasting studios. Key considerations involve room acoustics, the transmission of airborne and impact sound through building structures, the control of both airborne and structure-borne noise, and the management of noise from building systems and electroacoustic installations.

Bioacoustics

Bioacoustics constitutes the scientific inquiry into animal hearing and vocalizations, alongside the impact of acoustic environments and sounds on animal populations within their habitats.

Electroacoustics

This subdiscipline focuses on the electronic recording, manipulation, and reproduction of audio. Its scope extends to various products, including mobile phones, extensive public address systems, and virtual reality systems utilized in research laboratories.

Environmental noise and soundscapes

Environmental acoustics investigates noise and vibrations, assessing their effects on structures, inanimate objects, humans, and animal life.

The primary objective of these investigations is to mitigate environmental noise and vibration levels. Common research and professional activities in environmental acoustics involve the creation of simulation models, the refinement of measurement methodologies, the formulation of noise mitigation strategies, and the establishment of relevant standards and regulations. Contemporary research also emphasizes the beneficial integration of sound within urban settings, focusing on soundscapes and the cultivation of tranquility.

Illustrative sources of noise and vibration encompass railway operations, road traffic, aircraft, industrial machinery, and recreational pursuits.

Musical acoustics

Musical acoustics encompasses the investigation into the physics governing acoustic instruments, the audio signal processing techniques employed in electronic music, the computational analysis of musical compositions, and the perceptual and cognitive neuroscience aspects of music.

Psychoacoustics

Numerous investigations have explored the intricate relationship between acoustics and cognition, a field commonly termed psychoacoustics, which posits that auditory experience results from a confluence of perceptual and biological processes. Sound waves, upon traversing the ear, transmit information that the brain subsequently processes and interprets, thereby underscoring the profound link between mental states and acoustic phenomena. Research indicates that diverse auditory stimuli can induce psychological alterations, manifesting as changes in brainwave activity, which in turn influence an individual's thoughts, emotions, and behaviors. This correlation is observable in quotidian scenarios; for instance, an upbeat or fast-paced song might instinctively prompt foot-tapping, while a slower melody can evoke feelings of tranquility. A more profound biological examination of psychoacoustics reveals that fundamental acoustical properties of music activate the central nervous system. By analyzing the influence of acoustics on the central nervous system, comprising the brain and spinal cord, the precise mechanisms through which acoustics impacts the mind and, by extension, the body, become discernible.

Speech

Acousticians meticulously investigate the generation, processing, and reception of human speech. Within the realm of computational speech processing, speech recognition and speech synthesis represent two critical subfields. This discipline also intersects significantly with physics, physiology, psychology, and linguistics.

Structural Vibration and Dynamics

Structural acoustics involves the comprehensive study of mechanical systems' motions and their interactions with surrounding environments, alongside the methodologies for their measurement, analytical assessment, and regulatory control. This domain encompasses several distinct sub-disciplines:

Practical applications of structural acoustics include mitigating ground vibrations originating from railway systems, implementing vibration isolation techniques to minimize disturbances in surgical operating theaters, investigating the detrimental health effects of vibration (such as vibration white finger), employing vibration control strategies for seismic protection of structures, and quantifying the propagation of structure-borne sound within architectural spaces.

Ultrasonics

Ultrasonics pertains to the study and application of sound waves at frequencies exceeding the human auditory range. Key specializations within this field encompass medical ultrasonics (including diagnostic medical ultrasonography), the development of ultrasonic sensors, sonochemistry, non-destructive ultrasonic testing, material characterization, and underwater acoustics (specifically sonar technology).

Underwater acoustics

Underwater acoustics constitutes the scientific investigation of both naturally occurring and anthropogenically generated sounds within aquatic environments. Its applications are diverse, ranging from sonar systems for submarine detection and the study of whale communication to acoustic methods for monitoring sea temperatures in climate change research, the development of sonic weapons, and the field of marine bioacoustics.

Research

Professional societies

Academic journals

Conferences

References

References

Attenborough K, Postema M (2008). A Concise Introduction to Acoustics. Kingston upon Hull: University of Hull. doi:10.5281/zenodo.7504060. ISBN 978-90-812588-2-1.

Çavkanî: Arşîva TORÎma Akademî

About this article

What is Acoustics?

A short guide to Acoustics, its main features, uses and related topics.

Topic tags

What is Acoustics Acoustics guide Acoustics explained Acoustics basics Art articles Art in Kurdish

Common searches on this topic

  • What is Acoustics?
  • What is Acoustics used for?
  • Why is Acoustics important?
  • Which topics are related to Acoustics?

Category archive

Torima Akademi Neverok Archive: Art

Dive into a rich collection of art articles covering a vast spectrum of creative expression. Explore global art movements, from abstract expressionism to academic art, alongside the unique heritage of Kurdish art. Our

Art Kurdish Art Visual Arts Music Theory Art History Creative Arts

Related articles

Home Back to Arts