I worked as a welder in a car parts factory for 18 years and when the orders slacked off on the welding i'd be put into the press shop, this was 8 lines of about 6-7 power press's each about 30 foot high, a huge operation with chute's and conveyor belts in the basement to take the scrap away.
I used to take my ear buds out regular and not put them back in (really fucking stupid in hindsight) and suffer with a ringing in my ears as a result which comes and goes as you say happen's with your balance terry.330.
The noise was mental when i think back, the weight on the top and bottom tools in the press's ran into the tonnes on the heavy gauge lines, the smash when they connected was deafening, i couldn't talk to the guy next to me on the press because i just couldn't hear him.
Amazing to see a sheet of metal about 7 foot by 5 go through 6 press's and come out the last one looking like the bottom of a car.