[bitanarch]

Looked though Wikipedia a bit.. apparently this may be related to something quite common call Hypnagogia.

http://en.wikipedia.org/wiki/Hypnagogia

Look under the "Sounds" heading - makes a lot of sense to what I'd experienced. The loud sounds happen when I'm either transitioning from or to sleep.

Jumbled speeches is another thing I'd experienced during such a state - it feels like it makes perfect sense when you're in the state. But if something wakes you up or you're somehow able to summon your conscious thoughts, you'd find the speeches you just heard were just a random stream of words.