Many birds get into the mood for bathing or being sprayed when a vacuum is running nearby. Best guess is that it sounds like a rain storm in the jungle

But none of my birds respond to the sounds of a real rain storm, so who's to say?! And some of mine aren't moved by a vacuum either.
Others have given you good suggestions. Varying water temp is important. Some birds like it warm, some cold, some room temp. Most of mine preferring being sprayed to bathing, but some who love bathing hate being sprayed. Takes lots of experimentation. And some who hate water for years and years and years will suddenly go wild in it for no reason obvious to the doting mama

Never give up! But never torture your little guy either. Give him a chance to tell you what he likes and quit the stuff he hates after just a little bit of a try. 'Til next try.
Paca