II TRANSMISSION OF SOUND ENERGY AND THICKNESS OF PLATE TRANSMITTER AT NORMAL INCIDENCE—ULTRASONIC METHOD

Abstract

Another and more direct experimental method for determining the reflection from and transmission through parallel-faced partitions of sound energy of short wave-length was studied. Measurements were taken of the energy transmitted through obstructing plates by means of a torsion pendulum placed in the "ultrasonic shadow", the incidence of the energy being normal. The theoretical and experimental results obtained in previous researches by taking reflection measurements only were confirmed, and again it was shown necessary to employ the bulk modulus of elasticity for computations of velocity instead of Young's.