超音波音速測定における位相補正

概要

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In many techniques of sound speed measurement, sound propagation is regarded as plane wave in the medium. However, because of the finite aperture size, the sound wave does not propagate as an ideal plane wave. This deviation can be explained as a phase difference and as an amplitude difference, compared to the phase and amplitude of the planar transmitted sound wave. This position dependent phase difference will cause an error in transmission time measurement and thus in sound speed measurement. In this paper this phase difference is calculated in a liquid medium for the sound field of planar circular transducers and concave circular transducers. Also the sound pressure received due to reflection by planar reflectors normal to the axis of the transducers is calculated. It is found that for points on the axis of the tranducers, the error in transmission time measurement depends on the aperture size and does not depend on the transducer shape. For planar reflectors, at the same distances from the transducers, the error on transmission time measurement is greater for the concave transducer, than for the planar transducer with the same size and frequency. The experimental result is presented for the sound speed measurement in water medium.
社団法人日本音響学会の論文