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AssigneeAudiological Engineering Corporation
InventorDavid Franklin
Estimating the term…
Directional hearing in noisy environments is enhanced using small conventional microphones. In one embodiment a conventional first order bidirectional gradient microphone is employed in connection with a barrier to produce sound shadow at the rearward end of the microphone. In other embodiments such as hearing assistive devices worn on a person's head or body, the head or body of that person serves as the barrier. The result is a significant reduction in gain for all frequencies of acoustic energy emanating from generally rearward of the microphone. The sound shadow creates an apparent change of direction of arrival for rearwardly arriving acoustic energy, thereby making it appear to the microphone that the sound is approaching from the high attenuation 90.degree. direction. Two spaced bidirectional microphones worn on a person's body may be positioned to take advantage of this effect while simulating binaural hearing in an assistive listening device. A similar directional result is obtained with two conventional cardioid microphones mounted on a common casing to face in opposite directions. Electronic circuitry subtracts the output signal of the rearward facing microphone from the output signal of the forward facing microphone to render the combination highly directional. Case noise and other mechanical vibrations modulating the two output signals are nulled out in the subtraction process.
The method of converting a bidirectional pressure gradient microphone to a unidirectional microphone comprising the step of establishing a sound shadow for acoustic energy approaching the bidirectional microphone from a rearward direction to change the apparent direction of said approaching acoustic energy to a direction approximately to rearward wherein, the step of establishing includes positioning an acoustically opaque barrier rearwardly of and spaced from said microphone to be intersected by a longitudinal axis of said microphone.
A microphone system comprising:
A microphone system comprising:
A microphone system comprising:
For a first order pressure gradient microphone having a longitudinal axis extending in a forward direction and a rearward direction, and having a spatial gain characteristic with minimum gain for acoustic energy received from perpendicular to said longitudinal axis and substantially higher gain for acoustic energy received from said forward and rearward directions, a method for converting said first order microphone to a unidirectional microphone comprising the step of establishing a sound shadow for acoustic energy approaching the microphone from a rearward direction to change the apparent direction of said approaching acoustic energy to a direction approximately perpendicular to rearward.
Dependencies are inferred from the claim text.