I got to a gym with lots of different classes. I like attending certain ones, and try to go to those that best fit with my schedule. However, one particular instructor has her classes so loud that my ears physically buzz afterwards for hours and it's almost unbearably loud during. I mentioned it to the reception and the next week it was a bit quieter at the start and she mentioned someone had complained but throughout the class it gradually got louder and louder. I put earplugs in but it's still pretty bad. AIBU to make a more formal complaint?