Patent ID: 6134329
Filing Date: 2000-10-17
Classification: H04R

Abstract:
A method of adjusting the frequency response of a hearing aid to prevent unstable feedback comprising the steps of:(a) fitting the hearing aid to a patient;(b) inserting a probe tube microphone in the patient's ear canal;(c) generating a controlled acoustic signal;(d) measuring an acoustic signal received at the probe tube microphone at a plurality of hearing aid gains;(e) calculating a closed loop transfer function for each of the plurality of hearing aid gains;(f) calculating the combined open loop transfer function of the hearing aid and feedback path as a function of the plurality of hearing aid gains and corresponding closed loop transfer functions;(g) analyzing the phase response of the combined open loop transfer function to identify frequencies at which unstable feedback can occur;(h) computing a maximum stable gain for each of the frequencies identified in step (g); and(i) adjusting the frequency response of the hearing aid to have a gain less than the computed maximum stable gain at each of the frequencies identified in step (g).