It's pouring with rain here right now, a huge summer storm lashing the house, and I couldn't hear hiss if I tried.
In summer, I have my air conditioners on, and the noise floor is such that I am kidding myself to hear residual noise.
During the day, there's environmental noise which is far and away above the level of residual hiss and hum.
It's only during those late night, cool months, where everyone is asleep (and the refrigerator has gone quiet) where I can really hear (not measure) the residual noise of gear, be it preamps, power amps or sources.
It's a totally first world (audiophile nervosa) problem in real terms.