a bit of humor here for me : both bigger engines and turbos generally reduce noise pollution when compared to the other design choices available for that power

a bit of humor here for me : both bigger engines and turbos generally reduce noise pollution when compared to the other design choices available for that power envelope. the loudest engine? a small literage non-turbo high compression motor of some sort. the most famously loud race-car , the mazda 787b, had a 2.6 liter naturally aspirated motor. Small literage, small package, rotary. Fairly high compression. It deafened drivers. turbochargers can be made to be annoying by enthusiasts, sure -- but that energy they produce is in large part thanks to the damping effect of the energy scavenging that they enable. and as for engine size, as literage increases an engine developer has to do less to get the power they need -- that means they can use long and heavily dampened mufflers/exhaust systems, lower compression, lower RPM, less noise . Again, yes -- enthusiasts can ruin this, but the larger majority of these big motors are quieter/smoother than their counterparts that must go to extremes to meet the same power criteria.