A Timpani up close you can feel in your belly as though someone punched you lightly in the gut and you can wear earplugs all you want it isn't going to help you if the horn you play concentrates that shock wave in the reverse manner in which it allows your own notes to go out, probably much worse if your chosen note happens to match the note to which that particular timpani is tuned. From the bell end to your mouthpiece it's essentially an open channel with a very specific length chosen to match the pitch at which the whole thing resonates. Get close to that frequency and anything you (and others, such as timpani players) do will be amplified. Your puny outgoing breath will have to fight with the force of a grown man hitting a ~1square meter sheet of very taut skin. It's a pretty uneven match.
Do Timpani players themselves play with ear protection? (Pretty common for drummers in pop music.)
Incidentally, if someone is willing to pick it up, I still have a silver plated Yamaha slide sitting here that hasn't been used for years (one of my lungs isn't what it used to be). Free to a good home.