1 it's probably related to your exhaust. A new Muffler should quiet things considerably. Make sure that is the problem. A hole in the Catalytic converter or an exhaust pipe / manifold will contribute to your car running loudly.
#2 Check things like Oil, Oil Pressure and head gasket. Power steering fluid too. These things if they are low or damaged (gaskets) can increase certain engine sounds or contribute to whines when you steer.
#3 Insulate. If your car is older or cheaper it may not be as quiet as a newer or more expensive car. I have an 89 S-10 and it is super loud when compared to my 97 Eclipse which is a louder environment then my 06 Hummer. Technology is amazing and sound deadening can make the cabin a nicer place.