In accordance with one aspect of the present invention, a method for detecting a change in the performance of an audio signal processing path is disclosed. The method comprises: selecting a characteristic of a received audio signal indicative of its energy content; determining first and second predetermined values of the selected energy characteristic at respective first and second audio signal frequency bands; calculating a ratio of the first and second predetermined values for a reference time period and a test time period; and comparing the ratio at the reference time period with the ratio of the test time period to determine a performance change in the audio path.