Noisli - Noisli is a fantastic background noise and color generator for working and relaxing. Online soothing ambient sounds like White noise, Rain and Coffee Shop.
EarTrumpet - Volume Control for Windows
Noizio - Feeling that the noise of the big city is too much for you to bear?
Volume2 - Volume2 is an advanced Windows audio mixer, a complete replacement for the standard Volume Control.
zenmix.io - Ambient background sound generator
Sound Control - App-specific volume control