We hears a modification of the sound coming from some noise ocean floor so to speak....( the electrical grid of the house is an "ocean" of noise )
When engineer design the electronic component they do so trying also to decrease the noise floor of each electronic components composing an amplifier or a dac for example... It is always a trade off, because ANY new component will work but with a cost of his own in term of noise...It is a compensation business for the engineer to controls the effects of the noise....
Like you already know i am not a scientist, this is my experience and reading...