Acoustics

From Wikipedia, the free encyclopedia

Acoustics is the branch of physics concerned with the study of sound (mechanical waves in gases, liquids, and solids). A scientist who works in the field of acoustics is an acoustician. The application of acoustics in technology is called acoustical engineering. There is often much overlap and interaction between the interests of acousticians and acoustical engineers.

The word acoustic is derived from the ancient Greek word ακουστός, meaning able to be heard. (Woodhouse, 1910, 392)

...[A]coustics is characterized by its reliance on combinations of physical principles drawn from other sources; and that the primary task of modern physical acoustics is to effect a fusion of the principles normally adhering to other sciences into a coherent basis for understanding, measuring, controlling, and using the whole gamut of vibrational phenomena in any material.

Origins in Acoustics. F.V. Hunt. Yale University Press, 1978

Acoustics is the science concerned with the production, control, transmission, reception, and effects of sound. Its origins began with the study of mechanical vibrations and the radiation of these vibrations through mechanical waves, and still continues today. Research was done to look into the many aspects of the fundamental physical processes involved in waves and sound and into possible applications of these processes in modern life. The study of sound waves also lead to physical principles that can be applied to the study of all waves.

The study of acoustics has been fundamental to many developments in the arts. Some of these, especially in the area of musical scales and instruments, were only explained theoretically by scientists after long years of long experimentation by artists. For example, much of what is now known about architectural acoustics was actually learned by trial and error over centuries of experience and was only recently formalized into a science.

Other applications of acoustic technology are in the study of geologic, atmospheric, and underwater phenomena. Psychoacoustics, the study of the physical effects of sound on biological systems, has been of interest since Pythagoras first heard the sounds of vibrating strings and of hammers hitting anvils in the 6th century BC, but the application of modern ultrasonic technology has only recently provided some of the most exciting developments in medicine. The ear itself is another biological instrument dedicated to receiving certain wave vibrations and interpreting them as sound. Recent studies by Daniel Statnekov and others, study sound and its effect on the human brain. Harmonic frequencies in the form of binaural beats can effect the brainwave patterns of a person who plays an ancient Peruvian Whistling Pot to create a "trance state". Here are some public technical papers on this subject [[1]]

[edit] Divisions of acoustics

The following are the main sub-disciplines of acoustics:^[1]

• Acoustical measurements and instrumentation
• Acoustic signal processing
• Aeroacoustics: study of aerodynamic sound, generated when a fluid flow interacts with a solid surface or with another flow. It has particular application to aeronautics, examples being the study of sound made by flying jets and the physics of shock waves (sonic booms).
• Architectural acoustics: study of sound waves distribution in variously shaped enclosed or partly enclosed spaces with effects of sound waves on objects of different shapes which are in their way. Mostly concentrated on how sound and buildings interact, including the behavior of sound in concert halls and auditoriums but also in office buildings, factories and homes.
• Bioacoustics: study of the use of sound by animals such as whales, dolphins, bats etc.
• Biomedical acoustics: study of the use of sound in medicine, for example the use of ultrasound for diagnostic and therapeutic purposes.
• Environmental noise: study of the sound propagation in the human environment, noise health effects and noise mitigation analysis.
• Psychoacoustics: study of subjective reaction of living beings to sound, hearing, perception, and localization.
• Physiological acoustics: study of the mechanical, electrical and biochemical function of hearing in living organisms.
• Physical acoustics: study of the detailed interaction of sound with materials and fluids and includes, for example, sonoluminescence (the emission of light by bubbles in a liquid excited by sound) and thermoacoustics (the interaction of sound and heat).
• Speech communication: study of how speech is produced, the analysis of speech signals and the properties of speech transmission, storage, recognition and enhancement.
• Structural acoustics and vibration: study of how sound and mechanical structures interact; for example, the transmission of sound through walls and the radiation of sound from vehicle panels.
• Transduction: study of how sound is generated and measured by loudspeakers, microphones, sonar projectors, hydrophones, ultrasonic transducers and sensors.
• Ultrasonics: study of high frequency sound, beyond the range of human hearing.
• Musical acoustics: study of the physics of musical instruments.
• Underwater acoustics: study of the propagation of sound in water.
• Nonlinear Acoustics: study of large amplitude sound waves that propagate according to the Westervelt-Lighthill equation (in fluids) and analogous theories in other types of media (see parametric array).