Performance of isolated word recognition system for degraded speech

The performance of an isolated word speech recognition (IWSR) system is known to drop rapidly with increase in the degradation of the input speech. In this paper we propose a recognition scheme which adapts itself to mild degradations in speech. The scheme does not need apriori information regarding the nature and extent of noise. We suggest techniques which adaptively discriminate between noisy and noise-free parameters by using a selective weighting procedure in the final distance calculations. A suitable index is used to study the performance of the recognition system for small data sets. Our scheme lends itself to greater flexibility in handling degradations in speech input than do the existing recognition schemes. We illustrate our scheme by simulating an adaptive differential pulse code modulated (ADPCM) speech, where the main distortion is contributed by the quatization noise.