| 摘要 |
PURPOSE:To attenuate reverberation caused by a case, by inserting and placing an elastic material which is brought into elastic and annular contact with the inside peripheral surface of the case between a sound absorbing material and the opening side of the case. CONSTITUTION:An elastic material 3 consisting of silicone rubber, etc. is placed in a case 1. As for this elastic material 3, its outside peripheral surface forms a crest shape, and it is brought into elastic and annular contact cally with almost the whole surface of the inside peripheral surface 1b of the case 1. Also, in the same way as usual, a sound absorbing material 5 is placed in a back chamber 4 of a space between the elastic material 3 and a piezoelectric ceramic vibrator 2. According to such constitution, a sound wave for filling the inside of the case 1 can be attenuated, and reverberation time can be shortened remarkably in cooperation with its attenuating action by the sound absorbing material 5.
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