| 摘要 |
PROBLEM TO BE SOLVED: To reduce dispersion or deterioration in sound pressure by placing a circumferential edge of a piezoelectric diaphragm to an upper end of a circumferential part of a lower case, coupling an upper case with a sound hole to the lower case, and a disk spring whose middle part in the upper case is pressed into contact with a ceiling face of the upper case, whose circumferential part is pressed into contact with a circumferential part of the piezoelectric diaphragm and that has a through-hole in the middle. SOLUTION: A piezoelectric diaphragm 19 where a piezoeiectric ceramic board 17 is adhered to a metallic plate 18 of a large diameter is placed at an upper end of a circumferential wall 14 of a lower case 13 made of an insulation material, and a contact terminal 16 is pressed into elastically contact with a lower face of the piezoelectric diaphragm 19. A disk spring 26 having a 1st through-hole 25 in the middle and a plurality of 2nd through-holes 27 on the same circumference of a tilt face at an equal interval is integrated with an inner part of the upper case 21. Thus, 1st and 2nd spaces A, B are communicated by the 2nd through-holes 27 to form a resonance space and a sound with excellent low frequency characteristic is sounded from the sound hole 20. |
