Abstract: A computer system analyses audio data representing a user speaking words from a body of text and identifies occasions where the user mispronounces an expected phoneme. Mispronunciation of the expected phoneme is identified by comparison with a phonetic sequence corresponding to the text, based on a predetermined or user-selected language model. The system requires the user to read continuously for a period of time, so that the user cannot hide any tendency they have to pronounce the words of the text either incorrectly or differently to the expected phonemes from the language model. The system operates on the basis of comparing the similarity of the spoken sounds of the user with the expected phonemes for the body of text, and it is not necessary to convert the user's speech to text. As the computer system need only work with the similarity scores and the sequence of expected phonemes, it can be implemented in a computationally efficient manner.