The present invention provides adaptive lightweight acoustic signal classification for physiological monitoring applications. In an exemplary implementation, the total energy of a segment of an acoustic signal recording body sounds is first determined. For each of a plurality of signal classes (e.g., good, noisy, weak), the probability that the segment belongs to the signal class is then calculated using the total energy and profile data for the signal class. The segment is then assigned to one of the plurality of signal classes by reference to the probabilities. Physiological data are then selectively generated and outputted using the segment, depending on the assigned signal class, and the segment is selectively applied as feedback to update profile data for the assigned signal class.