For the development of echo-sounder which ascertain the relief of the sea-bottom efficiently, it is necessary for us to study into the effect of ultrasonic reflection and propagation characteristics.
　So we experimented in the laboratory on the acoustic characteristic of the ultrasonic echo-sounder.
　Through the analysis of this experimental results, we took electro-acoustic transformed efficiency of the transducers (ηea).
　The other side, margin (M) was expressed as follow:
　M=6.318×10-4E21.917
　where E2: out put voltage at recorder
　From this empirical formula, it was understood that recordable limit out put voltage was about from 40 to 50 voltages.
　By use of these results, we can take quantitatively reflection and propagation characteristic in water each frequencis ultrasonic waves.