Effect of continuous auditory feedback (CAF) on human movements and motion awareness.

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Continuous Auditory Feedback (CAF) can have profound effects when used to guide bodily movements. CAF is defined as auditory feedback that responds dynamically to continuous streams of data. A large number of studies have used CAF to communicate dynamic human efforts in the body. In contrast, this study uses motion sensor data at the knee and hip joints, which were converted to auditory sounds, to communicate the dynamic phases of walking gait through shifts in tonal brightness and loudness of two tones with harmonic relationships. As a proof-of-concept study, our aim was to determine if CAF mapped to hip and knee movements affects a person's gait. A total of 10 participants, five males and five females, participated in a gait analysis in a Biomechanics lab in relation to the various sound conditions. Quantitative results revealed that CAF has a significant effect on cadence. Notably, females had a higher cadence compared with males. Qualitative responses suggested that participants were aware of a relationship between the rotation of the knee and hip as the rise and fall of audio tonal brightness to concentrate or synchronize their gait. We defined this as a brightness-rotation relationship. Based on these findings, we propose future investigations to further understand and extend this brightness-rotation relationship and develop reliable models of CAF to support movement awareness for gait training and rehabilitation program. These investigations will inform future development of wearable systems of on-body sensing and auditory feedback for this awareness and rehabilitation.