I was really hoping that someone had found the magical quiet tractor. I am very noise adverse, however have never found a "quiet tractor". The closest would have been a International 140 that had been modified as a carrier for a piece of specialty equipment. The tractor never ran above fast idle and was quiet, however if you revved it up it was just as loud as most other gas tractors.
I will say that the newer tractor cabs are nice and quiet on larger machines. Most tractors I still wear hearing protection in the cab as they are still to loud for me. I am young, but my hearing with background noise is lousy, the thought of loosing my hearing scares me so I try to be extra careful.
The old 4 cylinder gasoline tractors with large industrial engines - Some used Continental engines & others were Masseys & Internationals. They pumped out tons of torque at low RPM - which means low HP. Some of them were very quiet. I've "heard" Internationals that I had to lay my hand on to make sure they were running.. These big block low RPM gassers were popular in the 1950 thru 70s and they did the same work their modern counterparts do. But they did it at a much lower RPM. Some of them idle at a couple hundred and work at a thousand.
The downside is that they tend not to have modern loaders, or power steering... and most have a regular manual gearbox with a limited number of gears. They require effort to operate. They do have a modern 3pt hitch. Or at least most do.
The upside is you can go to a tractor show and find one that some elderly dude has put his heart and soul into restoring good as new - and for a reasonable price. Not cheap, but reasonable.
Or if you want more modern conveniences (and I bet you do, I did) you can get a fairly quiet diesel from the 1970s thru about 2007 and just resolve to run it at low RPMs. Having lots of gears helps to do that. The newer models post 2008/2015 and later can't be worked at low idle as well because it loads up the pollution devices, but diesels from those earlier years can work forever at a fast idle.
On the hearing....just take care of it. I know that's weak advise, but apparently we can't do any better than that. Yet.
Today, our hearing can stay the same or get worse but doesn't repair itself well. Maybe not at all. So use real ear protection. Consider getting your hearing checked to get a baseline - changes in hearing happen too slowly to notice...which seems to be a large part of the problem. Use a good set of shooter or muffler style headphones that really do block sound energy. If you can hear conversation it isn't good enough.
And look into whether noise canceling or music buds are good for your ears or not. The jury is still out on both those. I bet if you start now you can keep your hearing intact.
rScotty
