Using a ripple wall to help blind people measure the water level in a container

The aim of this study is to determine whether swiping the ripple wall of a container can help blind people to measure the water level in it. Swiping the ripples on the wall of a container above the water level produces a different sound from doing so below the water level, and this difference in sound may be able to indicate the level of water in the container. Such sound differences associated with 27 3 D-printed containers with a capacity of 500 ml and various forms were recorded. One of the printed containers and a commercially available beverage container were tested by blind people to measure water levels in three operations. The experimental results reveal that the thickness of the wall affected the sound most strongly. The errors in the estimated water levels were significantly smaller when the containers was lifted and swiped than when it was lifted only. Practitioner summary: Lifting only is used by blind people to judge the fullness of a container. The experimental results reveal that the errors in the estimated water levels were significantly smaller when blind people lifted and swiped a 500 ml container with a ripple wall than when it was lifted only. Abbreviations: FA I: fast adapting fibers I; FA II: fast adapting fibers II; SA I: slowly adapting fibers I; SA II: slowly adapting fibers II.