Low-noise directional microphone system
AssigneeSound Design Technologies, Ltd.
InventorsJim G. Ryan, Brian D. Csermak
Life of this patent
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Abstract
A low-noise directional microphone system includes a front microphone, a rear microphone, a low-noise phase-shifting circuit and a summation circuit. The front microphone generates a front microphone signal, and the rear microphone generates a rear microphone signal. The low-noise phase-shifting circuit implements a frequency-dependent phase difference between the front microphone signal and the rear microphone signal to create a controlled loss in directional gain and to maintain a maximum level of noise amplification over a pre-determined frequency band. The summation circuit combines the front and rear microphone signals to generate a directional microphone signal.
Claims32
A directional microphone system for a hearing instrument, comprising:
- a front microphone that generates a front microphone signal;
- a rear microphone that generates a rear microphone signal;
- a low-noise phase-shifting circuit that implements a frequency-dependent phase difference between the front microphone signal and the rear microphone signal to create a controlled loss in directional gain and maintain a maximum level of noise amplification over a pre-determined frequency band;
- and
- a summation circuit that combines the front and rear microphone signals to generate a directional microphone signal.
A directional microphone system for a hearing instrument, comprising:
- a front microphone that generates a front microphone signal;
- a rear microphone that generates a rear microphone signal;
- means for implementing a frequency-dependent phase difference between the front microphone signal and the rear microphone signal to create a controlled loss in directional gain and maintain a maximum level of noise amplification over a pre-determined frequency band;
- and
- means for combining the front microphone signal and the rear microphone signal to generate a directional microphone signal.
A digital hearing instrument, comprising:
- a front microphone that generates a front microphone signal;
- a rear microphone that generates a rear microphone signal;
- a directional processor coupled to the front and rear microphones that implements a frequency-dependent phase difference between the front microphone signal and the rear microphone signal to create a controlled loss in directional gain and maintain a maximum level of noise amplification over a pre-determined frequency band, and that combines the front and rear microphone signals to generate a directional microphone signal;
- a sound processor coupled to the directional processor that selectively modifies the frequency response of the directional microphone signal to match pre-selected signal characteristics and generates a processed intended signal;
- a digital-to-analog converter coupled to the sound processor that converts the processed intended signal into an analog hearing aid output signal;
- and
- a speaker coupled to the digital-to-analog converter that converts the analog hearing aid output signal to an acoustical hearing aid output signal that is directed into the ear canal of the digital hearing aid user.
A method for reducing noise levels in a directional microphone system for a hearing instrument, comprising the steps of:
- generating a front microphone signal from an acoustical signal;
- generating a rear microphone signal form the acoustical signal;
- causing a frequency-dependent phase difference between the front microphone signal and the rear microphone signal to create a controlled loss in directional gain and maintain a maximum level of noise amplification over a pre-determined frequency band;
- and
- combining the front microphone signal and the rear microphone signal to generate a directional microphone signal.
Dependencies are inferred from the claim text.