活魚(試料ヤマメ)の超音波反射について

概要

論文の詳細を見る
In relation to the measuring of the reflection of ultrasounds from a fish, we have taken accurate measurements of the relationship between the swimming action and the reflection of ultrasounds, as made by the living fish, Yamame.The echo sounder used was a 50KHz ultrasound echo sounder, a directional projector having a 30° effective beam angle and a hydrophone having a 110° of beam angle.These experiments were made inside an anechoic tank. The dimensions of this tank were 200cm long, 140cm wide and 140cm deep.The measuring method was as follows:The swimming actions were measured by a dynamic strain gauge in connection with a U-gauge. A practical method is to use a reference target of known reflection loss (steel ball), placed at the same range as the unknown, and to compare the levels from the reference target and the living fish to be measured.The acoustic back scattering polar diagram of living fishes or anesthetized fishes could be obtained by measuring the echo level from the fish in all directions at intervals of 10° on the lateral plane.The results obtained are summarized as follows:1) There was little relationship between the swimming action and the echo level from a living fish, even though it may be obtained by the same aspect of living fish.2) On the polar diagram, the directions of maximun echo level are of a lateral aspect.3) We found little change in the echo level of the dorsal aspect.
日本水産學會の論文