Zwicker's loudness model has the following stages: (a) A fixed filter representing transfer through the outer and middle ear; (b) Calculation of an excitation pattern from the physical spectrum; (c) Transformation of the excitation pattern to a specific loudness pattern. The area under the specific loudness pattern is assumed to determine loudness. This paper presents some modifications and extensions to Zwicker's loudness model. Changes are made in: (a) The assumed transfer function for the outer and middle ear; (b) The way that excitation patterns are calculated; (c) The way that specific loudness is related to excitation for sounds in quiet and in noise. The revised model accounts more accurately than Zwicker's model for the way that equal-loudness contours change with level. It also provides a more satisfactory explanation of why the loudness of a sound of fixed intensity remains constant when the sound has a bandwidth less than the critical bandwidth (CB). Finally, the revised model is able to account for the loudness of partially masked sounds without the introduction of correction factors. The revised model has the advantage that the excitation patterns on which it is based are calculated from analytical formulae rather than by reference to charts or tables. This avoids discontinuities in the predicted values of loudness.
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