Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
The Noun Project - Creating, Sharing and Celebrating the World's Visual Language
Sound Control - App-specific volume control
Streamline icons - The world’s largest icon pack library - 100k icons and illustrations.
Power mixer - Power Mixer is a complete Windows volume control replacement.