[carpayments4life]

I used a liquid truck bed liner. Bed liner coating I removed my plastic wheel liners (on my MDX) and painted 2 coats on their hidden side.
If you're interested, here's a youtube review video, for paint-on bed liners...Trust this guy's videos

(MDX)...My tires had 7/32nds left and were getting noisy. The bed liner did not help and I replaced the Scorpion Verde tires with new Goodyear Weather Ready tires. New tires are significantly quieter than tires that are 1/2 worn down.

 

[carpayments4life]

I used a Db meter $15 before and after the coating that I put on the plastic wheel liners. I drove on the same stretch of new asphalt and saw only 2/10 Db improvement. So yes it did help, but it wasn't worth the labor.
My new 2019 Passport Touring is at 64 Db over that stretch of road.
My old 2007 MDX was at 69 Db with new Weather Ready tires and at 72 Db with Pirelli Scorpion Verde Plus tires that had 7/32nds life remaining (after the bed liner coating).

 

[carpayments4life]

I read Honda's research info on sound deadening road noise the 20" Passport rims have a sound deadening strip, but didn't know how well they worked until your comment.
Road noise goes down as the amount of rubber, between the rim and the road increases.
You mention the Db levels were the same, between your OEM 20s (with sound deadening strip) and that of new 18s (without the sound deadening feature). Effectively, the sound deadening strip equates to having more rubber between the rim and the road.
Now I need to find out if any Honda/Acura 18" rims have the sound deadening strip and can be used on my Passport. I haven't checked the rims sizes on newer Hondas/Acura, which might be designed to be more sound conscience.
More on Honda's R&D road noise