" Noises that can reduce the difference between the background ambient hum and sudden loud sounds include:
~ White noise- this is a continuous mechanical-type noise, like the gentle hum of a motor, that covers the whole hearing range of frequencies...
~ Pink noise- this noise boosts lower frequencies for those who find white noise too sharp, and is more akin to natural noises such as steady rainfall or wind rustling through the leaves in a tree...
~ Brown noise- this is even lower frequency noise, like thunder or a crashing waterfall. "

― , Design A Healthy Home: 100 ways to transform your space for physical and mental wellbeing