Welcome to the forum.
It is unlikely that increasing the foam thickness will have a significant impact on audible noise.
There are many paths for audible noise and focusing on one won't have the desired result.
There are LOTS of articles on noise reduction. Here is one:
https://www.powerandmotoryacht.com/boats/inexpensive-noise-reduction-on-your-boat
One thing that may have a big impact at a low cost is to locate and properly seal direct / unobstructed noise paths, such as holes, cracks or gaps, assuming those are not required for proper / safe boat operation.
