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Unwanted sound. Noise control is the process of obtaining an acceptable noise environment for people in different situations. These definitions and the words “unwanted” and “acceptable” suggest that criteria need to be established to…

A method of nondestructive testing and materials characterization that uses mechanical waves moving through materials. It is similar to seismology, except in being concerned with the scale of engineering structures, such as…

A mechanical wave of large amplitude, propagating at supersonic velocity, across which pressure or stress, density, particle velocity, temperature, and related properties change in a nearly discontinuous manner. Unlike acoustic…

Devices that employ surface acoustic waves in the analog processing of electronic signals in the frequency range 107–109 Hz. Surface acoustic waves are mechanical vibrations that propagate along the surfaces of…

The production, propagation, reflection, scattering, and reception of sound in seawater. The sea covers approximately 75% of the Earth's surface. In terms of exploration, visible observation of the sea is limited due to the high attenuation…

An instrument that utilizes focused acoustic waves to produce images of surface and subsurface features in materials, and to measure elastic properties on a microscopic scale. It has been used to image and measure local elastic…

An instrument that is sensitive to the interference of two or more acoustic waves. It provides information on acoustic wavelengths that is useful in determining the velocity and absorption of sound in samples of…

A device to measure the acoustic power or intensity of a sound beam by means of the force or torque that the beam exerts on an inserted object or interface. The underlying theory involves the concept of radiation pressure, which is…

An autonomous undersea vehicle that can be launched from submarines, surface ships, or aircraft to attack enemy submarines and surface ships. An acoustic torpedo is a sophisticated weapon. Its main components are a guidance and control…