A study of acoustic echolocation in complex gaseous environments by using acoustic antennas consisting of piezoelectric ceramic transducers in flexural vibration

Abstract

In this article, acoustic echolocation measurement method for measurements in complex and normal gaseous environments is described in detail. The advantages of this measurement method along with information about improving the characteristics and accuracy of measurements in complex gaseous environments are presented. When measuring in a complex structural environment, the accuracy of the measurement greatly depends on the shape of the radiation pattern of the ultrasonic transducer (antenna). Most suitable transducers along with their directivity patterns are presented. When measuring in a gaseous environment, acoustic impedances of transducers and the environment should be matched. Since the impedances of the transducer and the environment are different, matching layers are necessary to increase the effectiveness of the transmission of acoustic energy. This matching directly affects the amplitudes of the transmitted and received measurement signals. Information on how the acoustic transducer operates in air is presented. In addition, main requirements for the transducers of the ultrasonic measurement instruments are given. Types of the transducers for measuring long distances are presented and parameters of different types of transducers are compared. For measurements in air or gaseous environment, piezoelectric ceramic transducers in a flexural vibration mode are widely used. Details of the specific design of such transducers for measurement in air are presented. Radiation patterns for the most effective transmission of energy are also presented. Designs of unidirectional acoustic antennas are given. Diagrams for calculating the geometric parameters of the transducers in flexural vibration mode to obtain specific radiation patterns of transducers are presented. When acoustic measurement instruments operate in complex gaseous environments, measurement of the ambient temperature along the whole measurement channel is necessary. An ultrasonic level measurement system with a detailed measurement algorithm for operation in such environments is presented.