1. A physiological monitoring device, comprising: a sound capture system adapted to detect body sounds and generate an acoustic signal representing the body sounds, the sound capture system including a sound transducer positioned on a body, an amplifier, a filter, an analog-to-digital converter and automatic gain control; an acoustic signal processing system operatively coupled with the capture system and adapted to determine a total energy of a segment of the signal, calculate for each of a plurality of signal classes a probability that the segment belongs to the signal class based at least in part on the total energy and profile data for the signal class, and assign the segment to one of the plurality of signal classes based at least in part on the probabilities; and a physiological data output system operatively coupled with the processing system and adapted to selectively output, depending on the assigned signal class, physiological data based at least in part on the segment, wherein in response to assigning the segment to a good class, the output system outputs physiological data based at least in part on the segment.