AUDIX is a knowledge-based multimedia system for auditory discrimination exercises. The aim of AUDIX is to provide patients with a computer-based therapy system which they can use between sessions with the human therapist, at home on an 'on-demand' basis. It is centered around computer based cognitive rehabilitation therapy whereas most existing programs in this area are only used for assessment. The auditory discrimination exercise system is designed for adult people who are speech-impaired as a result of a stroke. These people have auditory perceptual problems. The nature of the perceptual problem is an inability to perceive differences between phonemes. This requires a type of therapy called auditory discrimination training. The system provides computer-based auditory discrimination training. Through the knowledge-based design the domain dependent therapy knowledge is separated from the system core and provides a way for the therapist to add new knowledge, as new stimuli, or to create a new knowledge base to provide special exercises for an individual patient. The AUDIX architecture is described and the advantages of computer-based therapy are discussed.