[GlennS]

I get that too, if I'm reading or writing then nothing short of shouting or a physical tap on the shoulder can bring me back to reality.

But I'm not convinced everyone can learn it. I know people who are light sleepers and get jolted awake in the night because of noise. You'd think if their brains could adapt to filter out the ambient noise then they would have for the situation. Regularly interrupted sleep is probably pretty annoying.