Patent ID: 6584206
Filing Date: 2003-06-24
Classification: H04R

Abstract:
A speaker apparatus for generating sound pressure, comprising:a pair of fixed electrodes; a vibrator arranged between the pair of fixed electrodes and separated therefrom by a spacing; and means for producing a driving signal applied to the fixed electrodes and producing a bias voltage applied between an electrode of the vibrator and the pair of fixed electrodes to cause a driving force corresponding to the driving signal to be applied to the vibrator, wherein each of the pair of fixed electrode is divided into a plurality of electrode pieces, wherein said means for producing a driving signal includes a transformer having a plurality of secondary outputs producing a plurality of driving signals applied respectively to the plurality of electrode pieces, and wherein voltages of the plurality of driving signals applied to the plurality of electrode pieces are weighted so that driving forces applied to the vibrator are proportional to a surface displacement distribution in a unique vibration mode of the vibrator given by: Îžm,n=sin&it;â€ƒ&it;m&it;â€ƒ&it;Ï€a&it;x&CenterDot;sin&it;â€ƒ&it;n&it;â€ƒ&it;Ï€b&it;yâ€ƒwhere m and n are integers indicating an order of the unique vibration mode of the vibrator, and where a and b are the lengths of the size of the vibrator in the x-axis direction and in the y-axis direction, respectively.