SOUND SHIELDING METHOD FOR ULTRASONIC SENSOR AND SOUND SHIELDING MEMBER BASED ON THE SAME METHOD

摘要

PURPOSE:To use an ultrasonic sensor even under high pressure and to constitute it at low cost by canceling acoustic waves passed through the two kinds of media by inverting phases while utilizing the characteristic of differing ultrasonic propagation velocity between the two kinds of media. CONSTITUTION:On the back of a disk-shaped ultrasonic sensor 1, a first ringular medium A with the almost equal outer diameter and thickness (d) is abutted, and at the central space of the first medium A, a second medium B with the equal thickness is fitted. In this case, ultrasonic waves emitted from the back of the ultrasonic sensor 1 are respectively passed through the two kinds of media A and B having different ultrasonic propagation velocity so as to be equally divided and therefore, the passed ultrasonic waves are canceled while inverting the phases each other. Accordingly, the sound pressure of the acoustic wave emitted to a third medium C is turned to 0 and almost shielded, and these medial A and B are operated as a sound shielding member. Thus, although the configuration is simple, a sufficient sound shielding characteristic can be obtained even under high pressure.