| 摘要 |
PROBLEM TO BE SOLVED: To most appropriately absorb noise generated by a noise source whose position is fixed. SOLUTION: The sound absorbing device 3 which is supported nearly perpendicularly above the nearly whole machine 1 generating the mechanical noise has as reverse surfaces reflecting surfaces 7 and 8 as a set of surface elements having an angle of <=30 deg. to a perpendicular reference line 4. The reflecting surfaces 7 and 8 form a perpendicularly upward pointed shape and are formed as the reverse surfaces of sound absorbers 5 and 6, and the reflecting surfaces 7 and 8 are smooth as to the wavelength of a sound wave. Under those conditions, noise which is statistically large in reflection frequency attenuates abruptly, so that the generation of the noise can be suppressed. The reflecting surfaces face each other at an angle <=60 deg. and can be formed into a circular conic surface or quadrangular cone surface.
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