Lightweight Low Frequency Loudspeaker for Active Noise Control
Patent Application, Filed 2 Mar 2001
DEPARTMENT OF THE NAVY WASHINGTON DC
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The invention described herein is a low-mass, light-weight sound generator with particularly good performance at mid and low audio frequencies. It is expected to find principal use in applications where mass is of crucial importance. It is capable of delivering the high acoustic levels, as required for sound generation or active sound control. The present invention uses a generally planar acoustic membrane as a diaphragm, the diaphragm being in tension and attached at its outer edge to a support frame which provides a soft boundary condition to the acoustic diaphragm. In a preferred embodiment, the support structure is an inflatable toroidal tube of rubber or rubber-like material. A polymer membrane is attached to the support structure by heat sealing the membrane in place. A voltage is applied to a piezoelectric bender-type actuator, which imparts axial displacement to a region of the diaphragm, causing resonance of the diaphragm in the desired frequency range.