Are noise levels commonly associated with suicide? If the noise levels around you are those of a bike, a dog, or music, then that's far from loud. In contrast, have you ever visited a construction site? When you say that one of the things you've tried to stifle the noise is earmuffs, I wonder about the way you're approaching this problem. There exist so many noise-cancelling solutions out there, yet you choose to go…
This comes across as terribly misinformed and condescending at the same time. Try living with someone with autism if you think sensory overload (noise or otherwise) cannot or should not cause real problems for people.
People are not wholly defined by their disabilities. In the case of someone with autism experiencing sensory overload, I expect them to build coping mechanisms because of their condition. Having a library of tools will improve their lives.