hi, its the blade breaking the sound barrier,or poor muffler.

Mostly the noisy 2-stroke engines. Not sure what it takes to soften the sound of a couple hundred explosions a minute, but cars do it. I imagine it would make for a lot of bulk, though.

An electric mower isn't that loud really.

In any case, one should probably not be cutting the grass at night, as it will be too wet likely.

Of course you're talking about a push-mower, because most riders do have headlights.

I find it very useful to cut the grass early or late using the lights, especially late in fall or early in spring, so I would like the headlights.

But as I've said before, I live-rural and don't have any neighbors near enough to be concerned about, I too think that gasoline powered mowers are far too loud. Unfortunately, to quiet them would rob horsepower and efficiency, something they have neither enough of.

Also cutting at dusk lets you be cooler. Depending on the dewpoint and how warm it will be overnight, the grass usually isn't wet at all, at least not until it gets really cool.

I used to mower in the evening using floodlights from the house. I figured the neighbors don't go to bed that early anyway. The biggest problem I always had was the mosquitos come out at dusk.