A 'perceiveded' sound level IS subjective. When you actually measure it with instrumentation then you have something you can compare with other sounds. Since all our hearing is affected by past exposure we will all hear things differently, or should I say with the same level of intensity or sound pressure level. I for instance had an incident many years ago which resulted in a partial hearing loss in my one ear. On the low end I have a 5% loss, not much really but its there and they were able to measure it, so that affects how I hear things. Each of us has had exposure to high noise levels in our past that will do the same. It could be listening to loud music 20 years ago when we were young, or from a previous job, or even something as simple as prolonged exposure to borderline high noise levels such as operating a tractor or other machinery for many hours a day. If your TC29D does not seem loud to you but it does to others, then maybe your hearing has already been affected and you should get it checked. Just because OSHA says you need hearing protection when exposed to 85dB or greater does not mean there is no damage to your hearing done at 84 or 83 dB, or even at 75dB.
Personally, I have made the choice to wear hearing protection whenever I operate my SS, tractor, backhoe, chainsaw, string trimmer, electric hedge trimmers, and even my little JD x534 26HP lawn mower. In the shop I use hearing protection when operating the router or the surface planer and some times with other tools.
My Hummer H1 was so loud in the cabin that I would wear ear plugs on long drives at speeds above 55 MPH. That 6.5 Detroit is only inches away from you and there is little if any sound deadening in those beasts. Driving the turnpike at 65 MPH (which is Max. speed for an early Hummer H1) you needed it. Around town at 30 or 40 MPH not so bad, but at 55 or better you had to yell to be able to talk with anyone else in the cabin.
Cheap insurance is the way I look at it. Once you lose it you can't get it back so why chance it?