Method of measuring and preventing unstable feedback in hearing aids

摘要

A "true" hearing aid transfer function, including feedback, is derived from measurements taken with the hearing aid fitted in a patient's ear canal. Closed loop transfer functions are calculated at several hearing aid gains without opening the internal circuitry of the hearing aid using a time domain Weiner optimal filter model. The combined open loop transfer function of the hearing aid and feedback path is then calculated. Once the open loop transfer function is known, potentially unstable frequencies are identified and maximum hearing aid gain settings are determined. The hearing aid transfer function and transfer function of feedback path are also calculated from the closed loop transfer function measurements.