To easily transmit intake noise and exhaust noise into a cabin space.
An intake duct 1 is provided with a bored opening 7, and provided with a transmitting member 8 capable of switching connection condition of the intake duct 1 and a core support 2 from non-connected condition to connected condition in response to the intake air pressure. The transmitting member 8 is constituted of a duct side contact plate 9 to be sucked to the opening 7 in response to the intake air pressure to seal the opening 7 while to be brought into contact with the outer surface of the intake duct 1, and a core support side contact plate 10 connected to the duct side contact plate 9 and to be brought into surface-contact with a core support 2 when the duct side contact plate 9 is brought into contact with the outer surface of the intake duct 1. The duct side contact plate 9 is formed with a projection 11 to be fitted in the opening 7 to form the same surface with the inner surface of the intake duct 1 when it is brought into contact with the outer surface of the intake duct 1.
Yoshiaki Naito
Cui Shu Tetsu
Toru Miyasaka