AKUSTISK OMVANDLARE AV EN RIKTNINGSKARAKTERISTISK OCH INNEFATTANDE EN ELEKTRETFOLIE ANBRAGT DIREKT PA EN MOTELEKTRODPLATTA

摘要

A rough surfaced backplate has deposited thereon a metallic electrode having a plurality of large areas interconnected by thin strips. The large areas are symmetrically located on opposite sides of the center of the metallic electrode. Furthermore, the distances between the areas is nonlinear. Superimposed on the metallic electrode is an electret foil having a uniform electrostatic charge deposited on the polymer surface thereof.