The word acoustics is derived from the ancient Greek word, which meant ‘ability to be heard’.
Acoustics is a branch of modern physical science, dealing exclusively with sound. It is concerned with the formation, transmission, reception, regulation and the impact of sound. In recent years, acoustics has been applied in technology. Acoustical engineering is the field which relates to such applications.
As sound consists of mechanical waves, transmitted in gases, liquids and solids, its origins began with the study of mechanical vibrations and their radiation through mechanical waves.
Research on acoustics was carried out to enquire into the mechanism of physical processes involved in waves and sound; it also included the possible applications of these processes in contemporary life situations.
Acoustics and its Various Branches
Acoustics too, like other scientific disciplines, has its branches. Acoustic measurement and instrumentations, acoustic signal processing are some of the more significant sub-disciplines in acoustics.
In addition, we have aeroacoustics, which refers to the study of aerodynamic sound, generated when a fluid flow interacts with a solid surface or with another flow. It has an application to aeronautics. For example, the study of sound made by flying objects and the physics of shock waves (sonic booms) is a jet-age subject indeed!
The study of acoustics – especially in the area of musical scales and instruments, were explained theoretically in science after centuries of experimentation by traditional musicians.
Acoustic technology also finds its application in many human activities: in the study of geologic, atmospheric, and underwater phenomena.
Psychoacoustics is the study of the physical effects of sound on biological systems. It is the study of the subjective reaction of living beings to sound, hearing and perception. Though known for centuries from the days of Pythagoras (6’h century BC), it has found its application only in recent years. Studies by Daniel Statnekov and others relating to the effect of sound on the human brain have concluded that harmonic frequencies in the form of binaural beats could affect the brainwave patterns of a person who plays an ancient Peruvian Whistling Pot to create a trance state”.
Yet another area is architectural acoustics, a study of distribution of sound waves in variously shaped enclosures of the buildings. The interaction of a building and sound, more particularly the behaviour of sound in a concert hall and auditorium, the sound in a factory or workplace all come under this area of study. Noise suppression is what one endeavours in designing, the multi-unit dwellings for the swelling humanity and human activity. Much of what is now known about architectural acoustics was actually learned by trial and error over centuries of experimentation by the traditional musicians and musicologists.
Bioacoustics
Bioacoustics is an emerging discipline which refers to the study of the use of sound by humans and animals. This was established by the Slovenian biologist, Ivan Regen. In an interesting study conducted in 1925, Ivan Regen put a male cricket behind a microphone and cricket females in front of a loudspeaker. He observed that the female insects were not moving towards the male but towards the loudspeaker!
The study of bioacoustics is concerned with, for example, whales, dolphins, bats etc. which employ sound for their locomotion and movements. This subject investigates the fascinating emanation and reception of sound in the animal kingdom which includes the human beings by referring to the organs of hearing and also to the physiological and neuro-physiological processes through which sounds are produced, received or interpreted. Attempts are made in bioacoustics to understand the relationships between the characteristic sounds that an animal produces and the environment in which they are used, as well as the functions they are designed to serve.
Some animals are found to make use of sound ranging from infrasound to ultrasound to send messages (e.g., sexual calls and alarm calls, warning natural calamities such as cyclones etc.) to conspecifics, which may or may not be heard by the human ears. Such messages are also aimed at intimidating the competitors. Bats and dolphins are particularly known for their echolocation capabilities which help them in avoiding obstacles and also in locating their prey or mates. Birds, known for their melodic chirps also send more complex messages.
In ancient India, there were people who could decipher the interspecies communications of birds and animals, as legends go. The most recent advances in bioacoustics deal with the relationships among the animals and their environment. They are also concerned with the impact of man-made (anthropogenic) noise found in cities and in urban forests affecting not only the human beings but also the entire flora and fauna.
There is also a special branch of bioacoustics, which is concerned with the underwater world (marine mammals, in particular) and which has come to be referred to as Under-Water Acoustics. Biomedical acoustics deals with the use of sound in medicine (e.g., ultrasound used for diagnostic and therapeutic purposes).
There is also a subject called “physical acoustics” which limits itself to the study of the interaction of sound with materials and fluids. This deals with new avenues in sound perceptions such as sonoluminescence i.e. the light emission by bubbles in a liquid, excited by sound. It also deals with the interaction of sound and heat, the thermoacoustic.
No doubt, the field of acoustics has thrown open new windows for scientifically investigating the relevance of esoteric concepts and practices of nada yoga in the Indian subcontinent. Nada or sound was considered as the primordial force behind the creation, preservation and destruction of the universe and hence worshipped as god or Brahma.
This article was published in ‘AYURVEDA AND ALL’ – January 2008 – Page 31, 32
Edited by Geeta Shreedar, July 20, 2021