Abstract: A measurement method for evaluating the disturbances in an audio signal or test signal (1a, b) by comparing it to an undisturbed reference signal (1c, d). After being prefiltered (2) using the transfer functions of the outer and middle ear, the input signals are converted to a time-pitch representation by an perceptually adapted filter bank (3). Squares of absolute values (5) of the filter output signals are calculated (rectified), and the filter outputs are convoluted with a spreading function (4). Convolution can take place either before or after rectification. Level differences between the test and reference signals as well as linear distortions of the reference signals are compensated for in step (7) and evaluated separately. In step (8), a frequency-dependent offset is then added in order to model the residual noise of the ear, and the output signals are spread over time (9). Part of this time spreading operation can take place directly after rectification in step (4) in order to reduce computing time.

Abstract: A hearing aid having an input transducer (2), a signal processor (3), an output transducer (4) and an adaptive filter (5) for generating a feedback cancellation signal (101) further comprises a norm estimator (10) generating a first norm signal (109) indicative of a norm of the electrical input signal and a second norm signal (110) indicative of a norm of a feedback-cancelled electrical input signal, a comparator for comparing the first and second norm signals and generating a difference value Nfbc?Nx and a decision unit disabling application of the feedback cancellation signal to the signal path of the hearing aid if the difference value is above a certain threshold value cth thus avoiding the feedback cancellation mechanism actually increasing acoustic feedback of the hearing aid. The invention also provides a method for reducing acoustic feedback of a hearing aid, a computer program, and an electronic circuit for a hearing aid.