A digital electronic stethoscope, comprising: an acoustic sensor assembly comprising a body sensor portion and an ambient sensor portion, said body sensor portion being configured to make acoustically coupled contact with a subject while said ambient sensor portion is configured to face away from said body sensor portion so as to capture environmental noise proximate said body sensor portion; a signal processor and data storage system configured to communicate with said acoustic sensor assembly so as to receive detection signals therefrom, said detection signals comprising an auscultation signal comprising body target sound and a noise signal; and an output device configured to communicate with said signal processor and data storage system to provide at least one of an output signal or information derived from said output signal, wherein said signal processor and data storage system comprises a noise reduction system configured to remove both stationary noise and non-stationary noise from said detection signal to provide a processed signal substantially free of distortions, wherein signal processor and data storage system further comprises an auscultation sound classification system configured to receive said processed signal and provide a classification thereof as at least one of a normal breath sound or an abnormal breath sound, characterized in that: said noise reduction system suppresses ambient noise by multiband spectral subtraction of said noise signal from said detection signal to provide said processed signal substantially free of distortions, and wherein said multiband spectral subtraction includes: processing individual frequency bands based on spectral characteristics of a target body sound and said noise signal, adjusting processing of a localized time window of said detection signal based on local Signal To Noise Ratio information to provide a processed signal, and smoothing said processed signal along adjacent time frames and frequency bands to reduce reconstruction distortions in said processed signal. an acoustic sensor assembly comprising a body sensor portion and an ambient sensor portion, said body sensor portion being configured to make acoustically coupled contact with a subject while said ambient sensor portion is configured to face away from said body sensor portion so as to capture environmental noise proximate said body sensor portion; a signal processor and data storage system configured to communicate with said acoustic sensor assembly so as to receive detection signals therefrom, said detection signals comprising an auscultation signal comprising body target sound and a noise signal; and an output device configured to communicate with said signal processor and data storage system to provide at least one of an output signal or information derived from said output signal, wherein said signal processor and data storage system comprises a noise reduction system configured to remove both stationary noise and non-stationary noise from said detection signal to provide a processed signal substantially free of distortions, wherein signal processor and data storage system further comprises an auscultation sound classification system configured to receive said processed signal and provide a classification thereof as at least one of a normal breath sound or an abnormal breath sound, characterized in that: said noise reduction system suppresses ambient noise by multiband spectral subtraction of said noise signal from said detection signal to provide said processed signal substantially free of distortions, and wherein said multiband spectral subtraction includes: processing individual frequency bands based on spectral characteristics of a target body sound and said noise signal, adjusting processing of a localized time window of said detection signal based on local Signal To Noise Ratio information to provide a processed signal, and smoothing said processed signal along adjacent time frames and frequency bands to reduce reconstruction distortions in said processed signal. said noise reduction system suppresses ambient noise by multiband spectral subtraction of said noise signal from said detection signal to provide said processed signal substantially free of distortions, and wherein said multiband spectral subtraction includes: processing individual frequency bands based on spectral characteristics of a target body sound and said noise signal, adjusting processing of a localized time window of said detection signal based on local Signal To Noise Ratio information to provide a processed signal, and smoothing said processed signal along adjacent time frames and frequency bands to reduce reconstruction distortions in said processed signal. processing individual frequency bands based on spectral characteristics of a target body sound and said noise signal, adjusting processing of a localized time window of said detection signal based on local Signal To Noise Ratio information to provide a processed signal, and smoothing said processed signal along adjacent time frames and frequency bands to reduce reconstruction distortions in said processed signal.