PSU Fan noise ratings

[Skiroy]

Im confused . Im trying to find the most silent 120mm fans I can. Imnot understanding if the higher the number the better or what? For example is a 22dba fan quieter than a 15dba fan? Are they refering to -22db and -15db?

 

[Winetree]

The number is the level of sound.
The lower the number the quieter it is.