Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Apparatus for measuring surface movement of an object that is subjected to external vibrations

Abstract: A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

Apparatus for increasing the quality of sound from an acoustic source

Abstract: An apparatus for increasing the quality of sound from an acoustic source comprises in one embodiment a hollow enclosure, an acoustic source, an acoustic guide, a pair of acoustic inlet openings, a pair of acoustic exit openings, and pair of acoustic paths, wherein the acoustic inlet openings separate acoustic waves from the acoustic source and direct the acoustic waves the length of the acoustic paths to the acoustic exit openings in such a manner as to increase the quality of sound, and especially bass sound, from the acoustic source.

Control of nonlinear effects in acoustic surface waves

Abstract: Theoretical and experimental investigations are made of nonlinear effects in acoustic surface waves with and without velocity dispersion. First, the results of the investigation of nonlinear effects in surface‐wave devices are reported. Second, it is shown that the nonlinear effects in acoustic surface waves can be controlled by velocity dispersion; namely, when the velocity dispersion of acoustic surface waves is increased, the nonlinear effects are reduced, and when the acoustic surface waves are free from velocity dispersion, the nonlinear effects are increased. The experiment was conducted with specimens of a 131°‐rotated Y‐cut X‐propagating LiNbO3, and the fundamental frequency was about 300 MHz.

Unusual Parametric Effects on Line Acoustic Waves

Abstract: Absrruct-Line acoustic wave (LAW) devices, in which waves are guided in a narrow region along an edge, permit one to achieve high local strains with relatively Little total power. One would expect to observe strong harmonic generation and parametric conversion, resulting from the fust-order elastic nonlinearity. However, first-order nonlinear effects are nulled out to a high degree by the symmetry properties of the LAW. Conventional pumping produces only small effects and second harmonic generation is weak. Pumping at one-half the usual frequency, however, interacts with the seconderder nonlinear elastic coefficient which is not subject to nulling and produces useful outputs which increase rapidly at higher frequencies. Experimental results obtained with a LiNb03 LAW device at 100 and 200 MHz are presented.