Back in the early 70's, I drove a 1966 Shelby GT350 most of the time (my '71 BOSS 351 was my Winter "beater"). I modified it for occasional track use, with a roll-bar, "R" model front apron, dual quads, and side exhaust. I was living in Detroit, and my girlfriend (who I eventually married) lived in Akron OH (where I grew up). I drove the Detroit-to-Akron trip every weekend to go see her. I noticed when I'g get home, my ears would ring for a long time (it seemed like hours, but was probably a lot less).
I decided it might reduce the noise level somewhat if I wore my racing helmet on the trip. I started wearing it, and the noise level reduction helped considerably. Never got pulled over for wearing the helmet, but, the Ohio Turnpike toll-booth personnel sure did give me some strange looks.
Jeff