Idea of Mute Icon
It is a classic mute icon. There is a basic speaker with the letter "x", or what could be a cross icon to the right of it. You can clearly see the back and front of the speaker. You would not think sound is coming out of this speaker.
This page contains the Mute vector icon, as well as variations of this icon in different visual styles, and related icons. All icons are in the flat vector style, however, differ by the line thickness, fill, and corner radius.