I have thought about that but want the testing to be representative. Saying something distorted with me wearing ear plugs will raise eyebrows out there.
Alan has given you as superb suggestion.
Let me relay the following experience.
At one time I worked in an area that has several reciprocating engines. They were methane powered and ran low pressure high volume blowers. They were very, very similar to these pictured below in a building almost exactly like this. These appear to be running generators however. And are newer though the old ones were Cats this size.
A sound level meter on A-wtd would show 105 to 110 db SPL depending upon where you were. It was a cacophony. It assaulted your ears. You could stand it for a minute or three though it was a bad idea. Now these engines might need mixture adjustments, the valves might start to get noisy any number of things. Your ears are so heavily distorted at these levels and the loudest thing masked so much you could tell almost nothing about details of how an engine you were next to was operating from sound.
Put on some over the ear muffs...........oh what a difference. It knocked the sound down 25 db or so. You could easily hear all kinds of mechanical details in the sound that was just a cacophonous roar previously. You could hear the slightest ticking of valves getting out of adjustment. You could hear a wrist pin going bad, you would gauge very well with some experience by sound if the mixture needed trimming up, or timing tweaked. In audiophile terms you went from a smeared roar to a wealth of fine, fine detail you could hear.
So your ability to hear rubbing or distortion or other issues with the ear plugs in will be about an order of magnitude better. It may be weird, but you'll see instantly it works. If you have some clean cotton balls handy, I suppose you could check out the effect with those with a low level of attenuation.
The plugs above for musicians that claim a more even response would be a good idea I think. But while I've been reading of you testing limits of phones by listening at high volume I've winced at the idea. So I think once you give it a try with some hearing protection you'll instantly see the benefit of it. You'll hear more about what is going on, not less.