Zens - Designing and Evaluating a Sonified Movement-Based Interface to Alter Body and Flexibility Perception in Yoga

Zens is a sonified movement-based interface that uses sounds from the ocean to sonify Yoga movements and allows altering the pitch of such sounds. Zens includes ocean sounds, that represents an element available in the ocean and mimicked these correspondence between ocean waves and Yoga cycle.  Each sound provide movement step-by-step guidance using a  flat continuous tone, designed in three pitch variations types — ascending (396Hz −963Hz), descending (963Hz − 396Hz), and constant (666 Hz). Zens is a Windows Application, and uses a kinect sensor to capture the movements.

Movement sonification: Zens uses a Microsoft Kinect sensor and the MS-SDK v2 library to detect users’ interactions. Users' interactions are extracted from the movements that the users do while practicing the yoga sequence. For the detection of movements, we extracted the position of the joints and its coordinates using predefined equations. A particular movement it is inferred when the relevant joints excel the specified threshold. We sonified the movements based on their type: Discrete movements — We calculated the current distance of the joint in real time. If this distance is greater than or equal to a threshold obtained during calibration, Zens plays the submerge sound. Continuous movements — For this type of movements it is necessary to sonify their trajectory, for which we used the cents metric. And for the manipulation of the pitch according to the different pitch variations, we defined a linear function. This function allows to subtly appreciate the change in the flat continuous tone heard in the background. This function is defined based on the value of the angle reached by the user at the time of making the movement and the value of the interval between the initial angle and the maximum angle calculated in the calibration part.

Evaluation methods:  We conducted two experimental studies — In the first study 40 yogis completed one yoga session in CICESE. Participants were randomly assigned to either use the sonified movement-based interface (experimental group) or practice in a conventional way (control group). —In the second study 21 yogis completed a yoga session using the two variations of pitch (ascending, descending); Also, the order of the conditions was randomly assigned.

Outcomes and results: We found that Zens outperforms yogis subjective experience when compared to the conventional way of practicing Yoga. Our results indicate that using an ascending pitch alters yogis flexibility and their overall body perception. 

Full demo showing how the yogis use the Zens prototype

We thank other collaborators involved in this project and our sponsors: