It sounds like it might be time to invest in a quiet humidifier. Or make some other noise to cover the humidifier noise.
What I mean is, can you use a big fan or something that won't bother you as much as the humidifier.
Gary's oxygen machine (that he has to use during sleep) makes an awful noise, and it is not the same noise, it goes something like this, WHOOOOSH - KA THUMP - WOOOSH - KA THUMP over and over again. I just lay in bed and keep listening for the whoosh or the ka thump over and over and over and over - well you get the picture - it keeps me AWAKE.
So, we got a BIG wind machine fan - it makes a huge amount of noise, but it is the same noise and doesn't change, so it becomes white noise and it covers the whoosh ka thump noise. That's the only thing that saves me from the whoosh ka thump, whoosh ka thump, whoosh ka thump ALL NIGHT LONG!