It is a human ear with the person's head not visible with a diagonal line across it. It can symbolize a lack of audio or auditory ability. There is no circle around the ear and the line cuts it in half.
This Deaf icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,100 icons, all in the same style and quality.