| 摘要 |
PURPOSE:To transmit vibromotive force of an piezoelectric vibrating element to a cone shaped diaphragm with less loss and to improve non-distortion maximum output sound pressure level by coupling the piezoelectric vibrating element with a top end part of the cone shaped diaphragm with high degree of coupling, making the quantity of eccentricity to become smaller. CONSTITUTION:The top end part of the cone shaped diaphragm 1 is provided with a folded part 4 by folding said top end part in the internal direction, to which a periphery part of the piezoelectric vibrating element 5 is bonded using a non-shrinking bonding agent, etc. so that the periphery will be contained in the folded part 4. In such a case, the bonded surface of the folded part 4 is made flat as far as practical so that deforming strain will not be given to the piezoelectric vibrating element 5. Generally, a wide-angle right circular cone shaped diaphragm 1 having a small bore of 10cm or below has only one 1/2 standing wave resonance shown by dotted lines, and the frequency fh shifts up and down with respect to an opening angle theta. In case where theta is 135 deg.+ or -5 deg., for instance, the frequency fh becomes in the vicinity of 4,000-5,000Hz and together with the peak of basic low sound resonance frequency f0, double-hump response is obtained. As a result, the sensitivity of output sound pressure level P0 rises by 4-5 dB, and high sound pressure of fh or above drops suddenly, thereby obtaining a kind of band pass filter characteristic. |
