I'm not an expert so I may have some of these terms wrong. But as I understand it - there are three
parts to sound insulation:
Barrier (stop sound waves) - anything dense and heavy
Transmission (vibration) - flexible
Absorption (soaking up the sound) - usually foam
I've found on
boats that barrier is the most important. Keep the sound at the genset! It turns out that very small openings pass almost as much sound as if there was no insulation at all. You can see this with any door. A door that's open a crack is a lot noisier than one that's shut all the way.
So I'd first see if you could build a tight
plywood cover at the sink cabinet bottom that leaves no openings. Caulk the cracks. There's also an amazing relatively new product used in construction called Green Glue. This is an elastic goop (green no less
) that you can put between two
sheets of plywood. It does an amazing job and is
cheap.
Green Glue is your soundproofing and noise reduction material
Carl