Improvement of Vibration Sensitivity by Tangential Vibration

A vibration sensitivity is usually defined by the minimum amplitude when a subject perceives the vibration with ω 1 which is the frequency of perpendicular direction on the skin surface. In this work, we are interested in how the vibration sensitivity at ω 1 is changed under the condition adding the tangential vibration with ω 2 which is the frequency of tangential direction on the skin surface. Through all experiments, we found that the vibration sensitivity at ω 1 = 8, 10, and 25 Hz is improved approximately 30% with the p -value of below 0.1% by an adequate setting condition of ω 2 = 3 Hz.