| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem wherein a reproduction frequency band is not changed freely. SOLUTION: A rear surface permanent magnet board 11 includes sound emitting holes 11a; and a belt shape multipolar magnetizing pattern. A first support member 31 includes sound emitting holes 31a and is arranged at the outside of the rear surface permanent magnet board 11. A slide shutter 41 includes sound-emitting holes 41a and is arranged at the outside of the first support member 31. A vibrating membrane 13 is arranged so as to face the rear surface permanent magnet board 11. By sliding the slide shutter 41, air stiffness on the rear surface of the vibrating membrane 13 is varied. COPYRIGHT: (C)2008,JPO&INPIT
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