I suppose like everything else it depends on the design, construction, and installation. A 60-70 foot salmon buy-boat has recently been assigned to the end-tie on our dock. It has a hydraulic bow thruster. When it leaves the dock, the skipper uses the thruster to pivot the boat out 90 degrees from the end-tie. The only sound discernible over the boat's main engine is the burbling of the water coming out of the thruster.
A boat that previously used this end-tie is a similar-sized charter yacht. Its three-woman crew docked this boat using fore and aft thrusters and a wireless hand-held controller. Same deal: hydraulic thrusters and the only discernible sound was the burble of the water.
On the other hand..... the 120' corporate yacht
Daedalus I was associated with on a project some years back had a very large electric bow thruster. While you could certainly hear the motor up forward in the crew's quarters and in the big galley immediately aft of them, from outside the boat all one heard was the burble of the water.
So maybe it's a matter of getting what one pays for.