The recognition of speech in noisy environments is critical to certain DoD systems now under development. Current preprocessors for speech recognition systems, such as those based on "linear predictive coding," are linear and therefore not effective in noisy environments. The objective of this project is to develop a nonlinear preprocessor for speech recognition systems that significantly improves the signal to noise ratio of the speech signal to be recognized. The nonlinear transmission line will be realized in software, although realization in hardware in FY91 should be possible. More specifically we will:1) Develop a nonlinear transmission line preprocessor that accurately simulates the mechanics of the inner ear at all sound pressure levels.2) Preprocess speech with the nonlinear transmission line and show that there is a substantial improvement in the signal to noise ratio.3) Assess the desirability and feasibility of creating either a digital or analogue transmission line on a chip and using it as a preprocessor in the CMU, BBN, or MIT DARPA funded speech recognition systems.