Active noise control classification system

A method for classifying and applying filters for active noise control in a hearing system having at least one feedforward microphone and at least one feedback microphone, at least one loudspeaker, at least one integrated circuit comprising a memory and at least one processor unit, at least one feedback audio path described by a feedback transfer function and at least one feedforward path described by a feedforward transfer function, comprising the steps of:

• a) receiving a first audio signal that is a feedback microphone signal at the at least one feedback microphone, and receiving a second audio signal that is a feedforward microphone signal at the at least one feedforward microphone;
• b) estimating the feedback transfer function by an adaptive algorithm based on a comparison of the feedback microphone signal and a loudspeaker signal;
• c) calculating at least one of a plurality of relevant properties from the estimated feedback transfer function;
• d) determining a level at the at least one feedback microphone in relation to a level at the at least one feedforward microphone;
• e) selecting, by a classifying algorithm, a set of filter coefficients based on the calculated relevant properties of the estimated feedback transfer function and the determined level of the at least one feedback microphone, either by outputting a discrete class assigned to a set of filters stored on the memory of the hearing system or by outputting a one-dimensional function that selects a set of filters stored on the memory of the hearing system;
• f) applying the selected set of filter coefficients as a feedback filter in a current feedback audio path;
• g) estimating the feedforward transfer function by comparing the received feedforward signal and the received feedback microphone signal using an adaptive algorithm to estimate the feedforward transfer function;
• h) calculating at least one of a plurality of the relevant properties from the estimated feedforward transfer function;
• i) determining a performance indicator by referencing the received feedback microphone signal to the feedforward microphone signal;
• j) selecting a second set of filter coefficients using the calculated relevant properties of the estimated feedforward transfer functions of step h) and the determined performance indicator of step i) as inputs of a classifying algorithm which uses them to select the second set of filter coefficients, either by outputting a discrete class associated with a set of filters stored on the memory located in the hearing system, or by outputting a one-dimensional function which selects a set of filters stored on the memory located in the hearing system;
• k) applying the second set of filter coefficients as a feedforward filter in a current feedforward audio path;
• and
• l) Readjusting the feedback filter and the feedforward filter by performing steps a)-k) again, or readjusting only the feedforward filter by performing steps g)-k) again.