Remora also has a noise reduction sponge that they include with all new models and will send to you upon request completely free. I received mine a year or so ago and I have no problems with the noise now on my Remora Pro.

I have a black sponge on the left side chamber, is this what you are refering to?

I believe so it is the chamber that has the venturi injection that receives water from the pump. Initially they did not come with the sponge that has an indentation to allow you to fit it around the tube that has the spray nozzel. It was very loud for me before this but is not loud at all for me after adding it.