| 摘要 |
PROBLEM TO BE SOLVED: To reduce unevenness of a vibration board, increase rigidity and extend reproduction frequency band without using high-strength materials or a special structure. SOLUTION: A speaker includes a vibration board which has a concave part on a surface thereof, and an additional vibration part which is arranged so as to cover the concave part of the vibration board in some parts of the vibration board and reduces the height difference of the concave part are provided. If Sd is a projection area of an effective area of the whole of the vibration board 170, Sr is a projection area of the additional vibration part, and an upper frequency is specified so that an output sound pressure becomes -10 dB in output sound pressure frequency characteristics, 1>Sr/Sd≥1/√10 is satisfied. COPYRIGHT: (C)2011,JPO&INPIT
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