[ridgeguy]

It may be that intolerance of loud noises isn't that the noise is painfully loud or otherwise physically irritating, but that it interferes with their ability to understand simultaneous auditory input.

I've noticed as I age that noise which I would formerly have disregarded without thought has become an irritant - that is, I can't/won't tolerate it - not because it's physically uncomfortable, but because my wetware apparently can no longer do the signal processing that earlier made such noise irrelevant to auditory comprehension.