computer - assisted auscultation of knee joints by auditory display of vibroarthrographic signals emitted during active movement of the leg include audification and sonification . in audification , the vibroarthrographic signals are scaled in time and frequency using a time - frequency distribution to facilitate aural analysis . in sonification , the instantaneous mean frequency and envelope of the vibroarthrographic signals are derived and used to synthesize sounds that may facilitate more accurate diagnosis than the original signals by improving their aural quality .