Robust speech recognition using missing data techniques in the prospect domain and fuzzy masks

Missing data theory (MDT) has been applied to handle the problem of noise-robust speech recognition. Conventional MDT-systems require acoustic models that are expressed in the log-spectral rather than in the cepstral domain, which leads to a loss in accuracy. Therefore, we have already introduced a MDT-technique that can be applied in any feature domain that is a linear transform of log-spectra. This MDT-system requires hard decisions about the reliability of each spectral component. When computed from noisy data, misclassification errors in the mask are hardly unavoidable and the recognition rate will significantly degrade. The risk of misclassifications can be reduced by estimating a probability that the component is reliable, e.g. a fuzzy mask. In this paper, we extend our MDT-system to be applied in the probabilistic decision framework. Experiments on the Aurora2 database demonstrate a further increase in recognition accuracy, especially at low SNRs.