This paper describes the design and development of a set of signal processing software tools for speech recognition. The tools were developed for inclusion in a comprehensive public domain speech recognition toolkit. We describe the design philosophy underlying the development of the tools as well as the key features that enable realization of our design goals of modularity, extensibility, and usability. A GUI-based configuration tool is presented that allows complicated, multi-pass front end algorithms to be created using a graphical editor and a library of fundamental algorithm components. We also discuss results of tests to verify the correctness and usability of the tool set, including benchmarks on SWITCHBOARD, WSJ0 and the Aurora Large Vocabulary tasks. KEY WORDS Signal processing, speech recognition, algorithm.