PNG MORE
Desktop apps
Pixel
Simply 8-bits #13
volume, plus
DarkSlateGray
96x96
UI
Windows 8 Pack (Metro Style)
Up, volume
26x26
volume, Down
PNG ICO ICNS MORE
Boolean
Mute, speaker, sound
16x16
volume, level
speaker, volume, Control
volume
Fugue Icons
speaker, volume, none