“…Respiratory sounds were recorded mainly from the posterior chest (right and left) [3,18,28e36,38e41], 5 studies recorded from the anterior chest [28,30,32,34,40], 6 from the trachea [29,31,33,35,38,39] and 1 from the nasal cavity [37]. Recordings were performed with the subjects standing [3,28,29,40], lying [18,31,33,36] or sitting [6,30,38,39], with different recording devices such as conventional [3,30,33,37,40], electret [28,31,32] and condenser [35] microphones, piezoelectric contact sensors [6,29,34,35,38], sound transducers [18] and contact accelerometers [39].…”