ELI5 Why would most of us awaken to a sudden noise but perhaps less so to a sudden light or aroma?

Question

So, we have 5 basic senses. When we’re asleep, I wondered why a loud noise would likely rouse us whilst a sudden bright light may rouse less of us and even less would probably wake up to a sudden odour.

In: Biology

Answer 1

There was a study done that seemed to prove that people lose their sense of smell when they’re unconscious. That’s why we need smoke alarms instead of just the smell of burning to wake us up.