SleepDeep muffles disruptive sounds like snoring and traffic, but it doesn't shut out the world. It has 27 dB of noise reduction, so sounds get softer, not silent. That means an alarm, a doorbell or a crying baby can still reach you, just at a lower volume.
How much you hear depends on the sound, how loud it is and how well the earplug fits. If you need to be sure you wake up for your kids or an early alarm, add a backup: a vibrating alarm, or a baby monitor set to a volume you can hear.