Experimental Study for the Utilization of Information of the Ultrasonic (50kHz) Pulse Shape of Echoes Reflected by Two Spheres

Abstract

In ordinary fish-finders, information of amplitude of echo pulse is mainly utilized. How-ever, the amplitude shows an irregular fluctuation on account of some factors, and the fluctuation gives bad influence upon the measurements. A reflected pulse shape contains combined information about amplitude, phase, and form of envelope. So, in this paper, by measuring the reflected pulse signal by two steel balls, the utilization-efficacy of echo shape (amplitude and form of envelope) was discussed. The measurements were carried out by using a 50 kHz fish finder in an indoor 45 ton-water-tank. In order to transmit the sound beam horizontally, a transducer was set up at the mid-water of the tank; and on the acoustic axis two balls were put at a distance of 2.1 m from the transducer. Received signals were analyzed by means of a signal analyzer. From these basic experiments, it was pointed out that it was possible for us to estimate the size of two balls and the distance between them, provided that these balls are within the range resolution decided by pulse duration.