Acoustic waves - phase shifter and noise barrier

摘要

PROBLEM TO BE SOLVED: To enhance a sound reduction effect by mutual interferences of sound waves by providing a sound insulating plate assembly supporting a porous member and forming plural independent space parts having different volumes on the back part of the porous member. ;SOLUTION: A cylindrical porous member 15 is provided at the outer circumferential part of a sound insulating plate assembly 14 consituted of first sound insulating plates 12 and second sound insulating plates 13. Plural independent space parts 16 having different volumes are formed on the back part of the member 15. The sound wave made directly incident on a sound wave phase changing device 17 and the sound wave made incident on the device 17 by being reflected on a sound insulating panel 11 pass through the porous member 15 to enter the space parts 16 and are reflected on the sound insulating plates 12, 13 constituting wall parts of space parts 16 and pass the member 15 to go out from the device 17 into outside. In this case, the phase difference between the incident sound wave and the reflected sound wave changes according to a normal acoustic impedance. Then, since it is possible to control the normal acoustic impedance by the device 17, the phase difference can be changed.;COPYRIGHT: (C)1997,JPO