no it doesnt canel hum or noise, what it does just silence your signal chain moment when it detect the presence of sound, as set by you , the user.
do more reasearch and read up on noise supressor, noise gate etc. It wont magically make what ever noise disappear. The key thing is to determine why are there so much noise, hum in your set up. Only when knowing that, you will/cann find ways to reduce it, before using a noise gate/supressor etc.
A noise supressor/gate is not a magik pedal. It act like a door, the gap of the door opening(noise supressing/gating), is determine by you(setting on the pedal). How it works is by closing this door to shut out the noise when detecting a certain level of normal geetar signal/noise/hiss etc.
How fast this door close or open when detecting noist and detecting your geetar playing, is set by user. Extreme setting, this noise supressing door will react really sensitive and cut off the trailing of your geetar signal, which is detected as 'sound" thats within the noise/signal limit that you set on the pedal.
Anyway, to use a supressor, first determne where do the problems of noise come from, then use it to taste. If just wanna cut down noise without knowing where did the noise come from, you will only go round and round in circle...