A New Measuring Method for Underwater Displacement Utilizing Sound Signal

摘要

This paper deals with a newly developed underwater displacement sensor utilizing the acoustic resonant frequency of water in a submerged pipe. Both ends of the pipe are closed. A speaker to generate sound is fixed on the end of the pipe with the reflector at the other end. A piezoelectric ceramic is used as a speaker. Sweeping signal is radiated from the speaker to the water column in the pipe. The sound pressure takes the largest value at the resonant frequency. The displacement of the reflector which is inserted from the other end of the pipe by the plunger, corresponds to the length of the water column. The displacement of the reflector has good correspondence to the resonant frequency of the water column. It is found from the experiment that it is possible to measure accurately underwater displacement using this sensor.