Digital hearing aid system

A system for reducing occlusion in an ear piece, comprising:

• a rear A/D converter that receives an occlusion signal from a rear microphone positioned within an ear canal and generates a digital occlusion signal;
• a summation circuit coupled to the rear A/D converter that inverts the digital occlusion signal to generate a digital output signal;
• and
• a digital-to-analog (D/A) converter coupled to the summation circuit that converts the digital output signal into an analog output signal for a speaker positioned within the ear canal.

A digital hearing instrument, comprising:

• a microphone that receives an acoustical signal and generates an analog signal;
• a variable pre-amplifier coupled to the microphone that receives the analog signal and also receives a gain control signal, wherein the gain control signal determines the value of a first gain that is applied by the variable pre-amplifier to the analog signal to generate an amplified analog signal;
• an analog-to-digital (A/D) converter coupled to the variable pre-amplifier that converts the amplified analog signal to generate a digital signal;
• a headroom expander coupled to the A/D converter that applies a second gain to the digital signal to generate a headroom expander output signal and that monitors an energy level of the digital signal to generate the gain control signal, wherein the headroom expander is configured to adjust the gain control signal to decrease the value of the first gain and to increase the value of the second gain when the energy level of the digital signal rises above a pre-selected level;
• a sound processor coupled to the headroom expander that amplifies the headroom expander output to generate a processed output signal;
• and
• and a speaker that converts the processed output signal into an acoustical output signal.

A method of optimizing the operating point of an analog-to-digital (A/D) converter in an input stage of a digital hearing instrument, comprising the steps of:

• receiving an analog audio signal from a microphone;
• applying a first gain to the analog audio signal to generate an amplified analog audio signal;
• converting the amplified analog audio signal into a digital audio signal;
• applying a second gain to the digital audio signal to generate a conditioned audio input signal;
• monitoring an energy level of the digital audio signal;
• and
• if the energy level of the digital audio signal rises above a pre-selected level, then decreasing the first gain and increasing the second gain.