I would agree with Barncat's assessment. We're currently having a lawn service doing our yard work since I'm temporarily unable.. For mowing the lawn they use a 20+ hp propane powered mower. While it probably burns a little cleaner than my 22 hp John Deere it makes just as much noise.
As for generators we've had 3 over the years. One is and older (circa 1980) Pincor 3,000 watt I originally bought when building a couple houses. It runs fine, but is an annoying screamer. The muffler is nothing more than something you'd expect to find on a Briggs & Stratton lawn mower engine. Our newest one is a 2013 Cummins/Onan 5500 watt. Mechanically it's much more quiet than the Pincor, and it has a muffler similar in size to the one on my JD. You can stand within 3 feet of it and carry on a conversation in a normal tone of voice.
The one I wish I still had is a Kohler 3,000 watt. It was the same vintage as the Pincor, but looking back was much better built, and far more quiet. The only downside was that it was unbelievably heavy. While it was supposed to be "portable" it was on it's own self contained skid, and took at least 2 strong men to move it. After moving it around from site to site for a couple years I got so tired of the weight I traded it off for the Pincor. That was a mistake. Not only was the Kohler much more quiet it had a "demand cycle". The engine would idle down when there was no load. Just a low rumble in the background. As soon as the "demand circuit" sensed a power draw it would come up to speed and remain at speed until there was no longer a demand.
I would look for something powered either by a Honda, Cummins/Onan, Suzuki, or Kohler. Over the years I've had over 50 pieces of portable equipment powered by just about every make of gasoline engine on the market. The longest lasting, quietist, lowest maintenance, most dependable were powered by these brand engines.
I'm not sure if Suzuki ever entered the generator market, but I have 2 small tractors powered by their 22 hp, twin cylinder, water cooled engines. They're both about 20 years old and as dependable as they come. They both start easily in temperatures ranging from -20F to 90+F and run all day long with minimal fuel consumption, plenty of power, and minimal maintenance. Small engines have come a long way in the last 30 years. The quality ones are still more expensive, but well worth the money in the long run.