Flow and noise
Keeping this in mind, there are several places to take note so that these noises are minimized.
If the overflow is sized too small, the water level in the overflow box can drop. This cause two problems. Firstly, the longer drop distance will cause the water to impact at higher speed, splash. Secondly, the high speed entry draws in gas bubbles, leading to a popping sound. Therefore a properly sized overflow is important to ensure the water overflows gently into the overflow box. (Wow. Three overflow in one sentence )
The noise of the splashing water will be