Iwao Honda

Vibro-Acoustic Characteristic of Cylindrical Shell Transducer Embedding Piezoelectric Elements

This paper presents the theoretical approach to predict the dynamic properties of a cylindrical shell transducer with finite length, Piezoelectric elements are embedded on the inner surface of the elastic shell at the constant pitch to generate the shell vibration in the specific circumferential eigen mode and to detect the incoming underwater sound through the shell vibration. Piezoelectrically excited vibration of cylindrical shell and its related sound radiation into water are discussed. Calculated frequency response function of the shell vibration, sound radiation efficiency and directivity pattern for the each eigen mode of the shell agreed well with the measured results. Shell vibration and associated electric output of the piezoelectric elements induced by the incident underwater sound wave are evaluated by the present method and these reisults are compared with the experimental data. Frequency response of the sum of the output voltage of the distributed piezoelectric elements induced by the incoming sound wave shows good agreement with measured results. Moreover, generated dynamic pressure distribution around the shell surface is measured and the comparison with the calculated results confirms the availability of the present theoretical method.

Analysis of vibro-acoustic characteristics of structures embedding piezoelectric elements and its application for height sensor.

This paper presents the theoretical method to determine the vibro-acoustic properties of struc tures embedding the piezoelectric elements. This method is based on the modal analysis technique that combines the vibratory characteritics of the structure, which is obtained by FEM calculation or experiment, and piezoelectric effect. Also taking acoustic radiation into consideration, fluid loading effect due to medium surrounding structures is included. As an example, vibratory and acoustic response of the transducer with node supporting devices are analyzed. Calculated results of electrically induced vibration, emitted sound pressure and directivity patterns agree well with the measured ones. Moreover, this node-support transducer with slight modification is applied to the ultrasonic ranging system, so called height sensor, for motion control of the high speed craft. Reduction of the self-noise induced by structural vibration and enlargement of the sound radiation power are achieved by use of this node-support transducer. The measured results of height show the good linearity and accuracy within the error of 0.04m.