I am a retired plumber and have dealt with a lot of Aqualisa showers. Is the noise what I call "mechanical" sounding or does it sound like water/air rushing around?
As far as the other answer you got to check if you have good flow just take the shower head off the hose and let it run. You don't actually say if, regardless of noise, the water is flowing properly or not. More info required to give a more informed solution.
David, October 2010