Patent ID: 8989412
Filing Date: 2015-03-24
Classification: H04R

Abstract:
1. A piezoelectric acoustic transducer that vibrates in accordance with a voltage applied thereto, the piezoelectric acoustic transducer comprising: a first non-vibrating fixed frame; a first piezoelectric diaphragm having first and second opposite surfaces and including a first board and a first piezoelectric element mounted on a main surface of the first board; a second piezoelectric diaphragm having first and second opposite surfaces and including a second board and a second piezoelectric element mounted on a main surface of the second board, the first surface of the first piezoelectric diaphragm and the second surface of the second piezoelectric diaphragm facing toward each other, and the second surface of the first piezoelectric diaphragm and the first surface of the second piezoelectric diaphragm facing away from each other, the first surface of the second piezoelectric diaphragm being not coupled with the first piezoelectric diaphragm, the second piezoelectric element being disposed at said first surface of the second piezoelectric diaphragm; a plurality of coupling members which couple the first piezoelectric diaphragm and the second piezoelectric diaphragm to each other and align a vibration axis of the first piezoelectric element of the first piezoelectric diaphragm with a vibration axis of the second piezoelectric element of the second piezoelectric diaphragm; and a surround which is capable of expansion and contraction and is disposed on the first surface of the second piezoelectric diaphragm in such a manner as to cover an entirety of the first surface of the second piezoelectric diaphragm from above the second piezoelectric element, the surround being configured to insulate an antiphase sound wave which is generated from a bottom of the piezoelectric acoustic transducer and which interferes with a sound wave emitted to the front of the piezoelectric acoustic transducer, wherein the polarity of each of the first and second piezoelectric elements is set so that the first and second piezoelectric diaphragms are displaced in directions opposite to each other, in accordance with a voltage applied thereto, wherein the first non-vibrating fixed frame is disposed at a position opposing the second piezoelectric diaphragm with the first piezoelectric diaphragm being interposed therebetween, and is coupled to the first piezoelectric diaphragm at a center of the first board, wherein the first non-vibrating fixed frame includes a beam, wherein a void is disposed on either side of the beam at positions under the first piezoelectric diaphragm, and wherein the coupling members couple the first piezoelectric diaphragm to the second piezoelectric diaphragm at end portions of the first board and along a direction perpendicular to directions in which the first piezoelectric element of the first piezoelectric diaphragm expands and contracts.