Patent ID: 6122389
Filing Date: 2000-09-19
Classification: H04R

Abstract:
A directional microphone, capable of being mounted flush to a surface of an object, comprised of:i) a microphone element having first and second acoustic input ports, said microphone element producing an electrical signal at an electrical output port;ii) a chamber, comprising two rigid halves of a housing, receiving said microphone element and acoustically separating said first acoustic input port substantially from said second acoustic input port, said chamber further comprising a first acoustic waveguide having a first acoustic input orifice coupling said first acoustic input port of said first-order gradient microphone element to said surface, a second acoustic waveguide having a second acoustic input orifice, coupling said second acoustic input of said first-order gradient microphone element to said surface, wherein a port separation distance is substantially equal to an effective acoustic separation distance of the microphone element and wherein said first acoustical waveguide and said second acoustical waveguide have substantially equal predetermined acoustic lengths, and wherein said first and second waveguides include means for providing substantially equal acoustical damping of a fundamental waveguide resonance, with the front input orifice of the first acoustic waveguide and the rear input orifice of the second acoustic waveguide being arranged on a planar exterior surface with each waveguide having substantially equal amounts of acoustic damping material, each said amount of acoustic damping material being arranged in a shape to fit inside the front housing and the rear housing such that a resonance peak is reduced to an appropriate level.