PNG MORE
UI
Pixel
Bijou
volume
Black
10x10
5x10
Windows 8 Pack (Metro Style)
Up, volume
DarkSlateGray
26x26
volume, Down
PNG ICO ICNS MORE
Boolean
Mute, speaker, sound
16x16
volume, level
speaker, volume, Control
Fugue Icons
Mute, speaker, Control
DarkRed
Control, speaker, volume
RoyalBlue
speaker, volume, none
speaker, volume, low
volume, speaker
Lynx Black
high, speaker, volume
medium, Audio, volume
volume, Audio, low
Audio, volume, muted
BWPX
Gray
18x18
Down, volume
volume, Mid
Gnome icons
Audio, low, volume
24x24