Mine isn't much louder than a typical SUV going 35mph down the street outside my house, if at all.

The town I live in has a railroad track running right down the middle, and at least two trains go by everyday (technically the same one going back and forth), is often overflown by military helicopters and we often hear artillery practice from the local army base rattling our windows. Combine this with the fact that a lot of my neighbors work odd hours, there isn't a time of day to run a lawnmower when someone isn't trying to sleep.