Separating heart sounds from lung sounds - Accurate diagnosis of respiratory disease depends on understanding noises

Heart sounds interfere with lung sounds in a manner that hampers the potential of respiratory sound analysis in terms of diagnosis of respiratory disease. This review categorizes 15 methods that have been applied for filtering heart sounds from lung-sound recordings as those that require a separate noise reference and those that do not, namely linear adaptive filters and filters employing time-frequency based methods respectively. Whether joint assessment of reduction in heart sounds and alteration to lung sounds by filtering was presented is determined for each study reviewed.