Rarely i use an alarm to wake me up at midnight (when needed) and i go to bed around 10pm. why my cell phone can't wake me up? am i deaf during sleep?

Not deaf.: Just asleep. Some people sleep deeper than others, that's all. You may need a louder alarm than your cell phone.

Impaired hearing.: You may have an impaired hearing for some reasons probably in one ear. See your doctor to get your ears checked.

Probably not,: but it wouldn't hurt to get a screening hearing test done by an audiologist. Your primary care physician can refer you to one.

Are you trying: to wake up after only two hours of sleep? Good luck. Assuming you are already sleep deprived you probably go right to sleep the moment you hit the pillow. That means that in 2 hours you would likely be in one of the deepest stages of sleep. Don't blame your phone. A cattle prod would not wake up most people 2 hrs into sleep. Get more sleep somehow. Get a minimum of 7 hours of sleep each night.

Deep Sleep: You are probably entering the "deep" sleep noted as REM sleep. You may need more sleep ..2 hrs is not enough

Why? WHY???: You're clearly not getting enough sleep on those nights. You're not waking up because your body and your brain need to rest. Two hours of sleep is just silliness. Don't do that.

Deep sleep?: Sometimes people cannot wake up at certain times during deeper stages of sleep, when they are very tired, or when their phone is not enough of a stimulus. Hope that helps!

Deep sleeper: during sleep, everyone produces brain waves called sleep spindles. We don't know why, but studies have shown that the more sleep spindles people produce, the deeper their sleep. Your probably one of them. As we get older, our sleep becomes lighter. So this will probably change in you.

No: You have a decreased ability to react to stimuli during sleep and depending on the actual stage of sleep you are in,it may become even harder to wake up and as such need a stronger (louder) stimulus. All senses are intact during sleep .

Deep sleep: If you go to bed at 10 pm and tries to wake up at Midnight, you are in a deeper stage of sleep and that makes it harder for you to wake up. Your cell phone has a hard time to wake you up because the depth of sleep you are in at that time. You are not deaf during sleep. If you have to wake up at mid night try to go to bed earlier in the evening.