| 摘要 |
PURPOSE:To extend the area of act effectively on sound absorption and to enhance the sound-absorbing effect by the diffused reflection of sound waves, by forming numerous projections of predetermined length on the surface of sound-absorbing members. CONSTITUTION:A baffle cover 5 is attached to a rotary electric machine proper so as to cover a cooling fan 4. To the inner surface of this baffle cover 5 sound- absorbing members 9-12 are attached. Situated on the side of a sound-absorbing room 7 and facing a protective net 6, the sound absorbing members 9 have numerous projected grooves 13 pointing upward and downward. The basic frequency of the noise produced by the rotation of the cooling fan 4 becomes the frequency equivalent to the product of the number of fliers of the cooling fan 4 and the number of rotation per a unit hour, so that at least the length of a part of projections is designed to be more than half the wavelength of sound waves with this frequency.
|
