That is interesting and sounds plausable. I actually experienced what you described on a few occasions in my life, and it kept progressing until the center part of my vision doesnt work and I couldnt read. It only happened to me two or three times.

I also experienced a milder form of what you describe when I stopped taking benzos, but that sideffect went away.

But generally I find walks in the park nice for the opposite of what you describe. Nature sounds do not stimulate or annoy me in the way background human noise does.