I have sensory processing issues and just got hammered with sensory overload. I was about to post a rant, but I think it might be more helpful to start a discussion.

So you know, we might better understand each other, or better understand characters with sensory processing differences of different kinds. I'm currently reading Bailey Summers' Encrypted, and Maddie comes to mind.

First off, sensory processing issues can be thoroughly disabling in our society. Consider how many streets are full of turn signals, car horns, brake squeals, and so on. Consider how many buildings and bus stations and so on are lit with strobing long-bulb flourescent lights, are full of flashing lights and flashing tv screens, beeping devices and beeping chimes, etc. Consider how much depends on phone calls. Everything seems to be built for one type of person, and can be inaccessible, in different ways, for other types.

Second, there are more variations than we really have words for. With any sense, there's a range from people whose brains tune out repeated signals to people whose brains turn up repeated signals. With sound, there's a whole range from deafness, and loudness recruitment, etc., through hyperacusis. I am practically tone-deaf, and can't handle the noise, while other people have perfect pitch and also can't handle the noise. I am probably more sensitive to certain types of noise than to others, though I am not sure how to compare. I know it can be hard for me, at the grocery, to hear people talk over the loud beeping noises. Of course, I have to wear ear protection to go there. I suppose it could be easier for other people.

Third, there are a lot of causes. I grew up with sensory differences, probably autism-related. I don't think my senses were necessarily more intense, but they were already mismatched to the built environment. I later suffered some still-undiagnosed chronic illness which has made my senses much more intense. I think ptsd, anxiety, migraines, fibromyalgia, Lyme disease, multiple sclerosis, etc. can all make senses more intense, acoustic shock, bone loss in the middle ear, Bell's palsy, etc. can make hearing in particular more intense.

Sharon Heller's "Too Loud Too Bright Too Fast Too Tight" is a useful first resource, though it only covers some of the variation.