Not sure what you define as 'road noise'. The road itself is basically quiet. Your tires can make noise, your (especially manual) transmission can make noise and your (car's) rear end can definitely resonate some noise. Yes, some of this can be 'masked' - but I would get to the root of the particular offender. Factory didn't need to add acres of insulation (other than original jute) so why should we?
My Signet's only evident noise while driving is from around the doors and or side windows - due to original weather seal having shrunk slightly. Quarter windows also major culprits. Me? I would correct any wind noise first and then correct whatever driveline component noise.
