My daughter is 4 months old and absolutely loves the sound of both our (very cheap) hair dryer and our (even cheaper) vacuum cleaner. I think it is essentially white noise to her, as she also loves the sound of running water. We know a couple where the father actually made a 30 minute mp3 of their hairdryer blowing to get their daughter to sleep.
That being said, even I cannot stand the sound of hand dryers in public restrooms. To me, it basically sounds like an extremely hysteric hair dryer. I wonder if it has anything to do with the fact that they are mounted on a wall, which gives them more resonance.
My parents used to use the vacuum cleaner to put me to sleep as a kid, even into my toddler years.
One night they forgot to turn it off and the motor burnt out.
To this day, I sleep (and often concentrate) better with some white noise going - turning on the bedroom fan is an essential part of my night-time ritual. There's some evidence that loving white noise is linked to ADHD, but I don't think that it's predictive for a 4 month old. :P
Newborns like loud environments. A birth changes environment for child from very loud to a very quiet. I suppose it feels like sensory deprivation for a child. Seems that hand dryer reminds your daughter a good old times before her birth.
That being said, even I cannot stand the sound of hand dryers in public restrooms. To me, it basically sounds like an extremely hysteric hair dryer. I wonder if it has anything to do with the fact that they are mounted on a wall, which gives them more resonance.