Observation of phase advance due to diffraction of ultrasonic pulse

概要

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Pulse-echo-overlap method has been applied to detect the phase advance due to diffraction. Two quartz transducers with electrodes 5 mm in radius have been used for a transmitter-receiver system with one-way path length 62 mm. Experiment has been made at 3 MHz and 9 MHz in methanol-water mixture as varying its concentration. Roundtrip travel time obtained at 3 MHz is by 14. 5 ns shorter than the value at 9 MHz when the velocity is 1497 m/s. The difference in reciprocal of the travel time has been detected and plotted as a function of velocity. Outline of the results is described well by diffraction theory. The experimental curve has, however, small peaks occurring periodically, which can not be predicted with diffraction teory nor with wave-guide theory. Further experiment made using a cell with larger inner diameter suggests these peaks are somewhat related to the limited space of sound propagtion, but clear explanation has not been given.
社団法人日本音響学会の論文