| Section A | A index | 121-129 of 917 terms |
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acoustic resonance—A condition of an acoustic system, such as a Helmholtz resonator, in which the response of the system to sound waves becomes very large when the frequency of the sound approaches a natural vibration frequency of the air (or other material) in the system.
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acoustic reverberation—The prolongation of sound after the original source has stopped vibrating in an enclosed space.
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acoustic scintillation—Irregular fluctuations in the received intensity of sounds propagated through the atmosphere (or ocean) from a source of uniform output; produced by the nonhomogeneous structure of the atmosphere (or ocean) along the path of wave propagation.
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acoustic signature—The characteristic pattern or profile of an object, such as a specific feature of the ocean floor, as detected by identification equipment that uses sound or ultrasonic waves.
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acoustic sounding—1. The technique of remote sensing in which an instrument sends acoustic waves vertically and receives reflections from atmospheric features such as inversions or turbulent layers. 2. A representation of the vertical profile of one or more of the state variables of a fluid body (typically the ocean or atmosphere) deduced from variations in reflected acoustic energy. 3. A particular measurement of depth of water below an instrument (either at the surface or at some moored depth) computed from the travel time of an acoustic pulse emitted by the acoustic sounder.
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acoustic tomography—An imaging technique in which information is collected from beams of acoustic radiations that have passed through an object, generally in the form representing a two-dimensional slice through the object. In oceanography, acoustic tomography consists of an inverse technique that uses acoustic signals to sample the interior of the ocean. In this way, the temperature structure of the interior ocean can be reconstructed from acoustic signals in multiple vertical planes.
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acoustic transponder—A device used in underwater navigation that responds with an acoustic code when interrogated by an acoustic signal from a ship.
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