  Human maintain their body balance by sensorimotor controls mainly based on
information gathered from vision, proprioception and vestibular systems. When
there is a lack of information, caused by pathologies, diseases or aging, the
subject may fall. In this context, we developed a system to augment information
gathering, providing the subject with warning audio-feedback signals related to
his/her equilibrium. The system comprises an inertial measurement unit (IMU), a
data processing unit, a headphone audio device and a software application. The
IMU is a low-weight, small-size wireless instrument that, body-back located
between the L2 and L5 lumbar vertebrae, measures the subject's trunk
kinematics. The application drives the data processing unit to feeding the
headphone with electric signals related to the kinematic measures.
Consequently, the user is audio-alerted, via headphone, of his/her own
equilibrium, hearing a pleasant sound when in a stable equilibrium, or an
increasing bothering sound when in an increasing unstable condition. Tests were
conducted on a group of six older subjects (59y-61y, SD = 2.09y) and a group of
four young subjects (21y-26y, SD = 2.88y) to underline difference in
effectiveness of the system, if any, related to the age of the users. For each
subject, standing balance tests were performed in normal or altered conditions,
such as, open or closed eyes, and on a solid or foam surface The system was
evaluated in terms of usability, reliability, and effectiveness in improving
the subject's balance in all conditions. As a result, the system successfully
helped the subjects in reducing the body swaying within 10.65%-65.90%,
differences depending on subjects' age and test conditions.
