Assessment of the Smoothness of Surfaces with an Acoustical Probe

The feeling of smoothness during the touching is delivered when the finger is rubbed on the surface. A static contact cannot provide such an information. The roughness noise, that is the friction noise generated during the sliding of two rough surfaces, is therefore the key phenomenon for the feeling of smoothness. To this end, a triboacoustical probe has been designed. This is a sort of artificial finger whose load is controlled and equipped with a microphone to measure the Sound Pressure Level. When rubbing the probe on various surfaces, it is possible to compare the acoustical level and therefore to assess the relative smoothness of the surfaces. Among them, some results are presented on skins with different ages, on different parts of the body, on skins before and after cleaning by acetone. Finally, this method is applied to assess the efficiency of cosmetics.