It's likely a combination of many factors.

There are several physical changes in water with higher temperature. It is much less viscous, slightly less dense, has reduced surface tension, and has a higher vapour pressure, so it breaks into more smaller drops rather than fewer large ones. So it hisses rather than rattles.

Also, the surface it is hitting changes its rigidity because it now has a thermal stress - it becomes hot at the surface where the water is directed but stays cooler in deeper layers (if thick like ceramics) and in the surrounding surface. That has to change its acoustic properties.