My 2004 BMW did this mechanically: there was a tube connecting the passenger compartment with the air intake to pipe in that sweet engine noise. (There was a me

My 2004 BMW did this mechanically: there was a tube connecting the passenger compartment with the air intake to pipe in that sweet engine noise. (There was a membrane inside to prevent actual airflow). Interestingly, the sound was actually too loud, so they stuffed some foam blocks in the resonator pipe to deaden the sound. But if you really wanted extra noise just remove the foam!