Dynamat is used for car interiors and is very easily available. My brother has that in his Taylorcraft and it works very well to quiet it down inside.
Noise canceling headset;-)
My A20 helmet comm works perfectly. The same is true in the 180, but I will say Zulu 3s are superior to 2s, but both are pretty damn good. We’ve come a very long way in the last 25 years!
Automotive undercoating.Anyone know what that black gunk was that Piper used back in the day?