I found the sound entered the room thru the pvc plumbing. I use my room as a sanctuary so I had problems using HP longer.I would rather get 15% less and a lot more reliability. I will see what you get over your other LP grows. If you get 1/3 more I will have to invest time in dampening that pump. I was thinking about using some parts from this system, . I make a tank that is 5' x 5' x 18" I was thinking of running 4 plants in it with those foggers.
In my gm1000 I run a 1/2" 7/24 low volume water line for the mat at the bottom. I am about 3 lbs every run per plant,if I could get 3.5+ I would change my room.
Clean work on your pump housing. I was lucky enough to get a roll of rubber for soundproofing from an old friend. I sandwich it in between soundboard. I used to use silicon in between.
Good luck on your project, JK