Bitten when sleeping

The question is right below. To begin with I must admit that I was negligent and died completely by my own fault. I slept in a military surplus bed after clearing zeds for quite a while and nothing was around me anymore, when I was sleeping I heard the window next to me get broken and I was spamming everything to try to and wake up and finally woke up when the zombie bit me.

Question : How come my character didn't wake up when a window was broken very near me ? Was he too tired to wake up, and would have woken up if he had been less tired ? Or do you just never wake up when something like that happens. I remember one time waking up in the middle of the night because of a nearby gunshot, and I can't help but think that in real life I absolutely would have jumped out of my bed if a window was smashed next to me, especially in a god forsaken apocalypse...