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 is a Deaf Filled icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,700 icons, all in the same style and quality.