Sonification of knee-joint vibration signals

Sounds generated due to rubbing of knee-joint surfaces may be a potential tool for noninvasively assessing articular cartilage degeneration. In this paper, an attempt is made to perform computer-assisted auscultation of knee joints by auditory display (AD) of the vibration signals (also known as vibroarthrographic or VAG signals) emitted during active movement of the leg. The AD technique is based on a sonification algorithm, in which the instantaneous mean frequency and envelope of the VAG signals were used in improving the potential diagnostic quality of VAG signals. Auditory classification experiments were performed by two orthopedic surgeons with a database of 37 VAG signals that includes 19 normal and 18 abnormal cases. Sensitivities of 31% and 83% were obtained with direct playback and the sonification method, respectively