Acoustic Characteristics Depending on the Vibration Distribution of Ultrasonic Sensors

This paper deals with acoustic directivity according to vibration displacement distribution of ultrasonic sensors for distance measurement. It is necessary to determine the vibration displacement distribution improving the directivity because the measurable distance is longer with better directivity, which depends on the vibration of the ultrasonic sensor’s housing plate. Directivity for circular housing plate with uniform vibration displacement distribution was theoretically expressed. Vibration displacement distribution and acoustic characteristics of real ultrasonic sensors were obtained by finite element analysis. Functional distribution of vibration displacement and sensor symmetry were considered in the analysis. As the vibration displacement distribution is gentle and approaches the uniform one, the ultrasonic sound pressure level in the direction of central axis is large and acoustic directivity is good. We have achieved the basis of improving the acoustic directivity for design of long-distance ultrasonic sensors.