1. A method for detecting speech activity for a signal, the method comprising the steps of: extracting a plurality of features from the signal; modeling a first and a second probability density functions (PDFs) of the plurality of features, wherein: the first PDF models active speech conditions for the signal, and the second PDF models inactive speech conditions for the signal; adapting the first and second PDFs to respond to changes in the signal over time; probability-based classifying of the signal based, at least in part, on the plurality of features; and distinguishing speech in the signal based, at least in part, upon the probability-based classifying step.