water noise

Hi guys, I bought a secondhand reefer 250. The previous owner rebuild the sump. Now there is extra space for more water on te right side, very lovely. However, on the spot where the water goes down into the pre-existing sump section there's a lot of noise. Does anyone have any suggestions on...

I have an external skimmer and the feed returns back to my sump. The return water flow has a lot of bubbles and as such it makes quite a bit of noise. I thought of a sponge in the pipe but that would end up and a nutrient trap I think. Any ideas on a solution?