| 摘要 |
PURPOSE:To eliminate the irradiation of only a harmful frequcncy by providing a hole-type frequency band cut-off resonance mufler provided with a holed cylinder, which has a diameter smaller than that of a buss reflector-type low frequency reinfocing duct and forms an annular space between said duct and its innte peripheral surface, on some part of the inner peripheral surface of said duct. CONSTITUTION:A cylindrical holed-type frequency band cut-off resonance mufler 9 fitted on the enitire inner peripheral surface of a buss reflectro-type duct 7 is constituted of a holed cylinder 11, whicg has a diameter smaller than that of said duct 7 and forms an annular space 10 between said duct 7 and its inner peripheral surface, and a fitting flange board 12 provided on both outer peripheral edges of said cylinder 11. The resonance mufler 9 is produced by, for instance, metal or molded resin. A circular or rectangular foled part 14 for extending the circular space 10 at certain foling depth is formed on each hole 13 of the cylinder with holes 11. With such constitution, the resonance mufler 9 provided on the buss reflector-type duct 7 can attenuate the irradiation of a hurmful wave, and the disturbance of a sound pressure frequency characteristic and directivity characteristic can be reduced. |
