Why can't/don't we make standard lawnmower engines quiet?

Question

For several decades we can make auto engines of hundreds of horsepower that run quietly; almost silent. Why dosen't/can't a standard, 3.5 HP mower engine run closer to being quiet?

Answer 1

its actually the exhaust and muffler which makes the motor loud/quiet.. if we took the exhaust system off a car engine.. it would blow your ears out it would be so loud... but lawn mowers have such little mufflers/exhaust systems that it wouldnt make a difference if there is or isnt one. so a larger exhaust/muffler would greatly reduce the noise level of a small mower engine.