I have an Aquaclear 70 that was noisy out of the box and that became somewhat quieter over time. Many people have told me that theirs are silent and when they hear mine -- in its 'quiet' version -- they tell me to take it back. But I bought it online, so it's tough.
One thing, though -- your Aquaclear should restart after it's been switched off, as long as it's in water. When my Aquaclear 70 wasn't filling itself, I discovered that I had to press the intake tube in much more firmly. I pushed it firmly towards the filter and also downwards. Once it is in the right position, even if it doesn't look like it's differently situated, it should refill itself. Perhaps your filter will also be quieter once you've done that.