Wearing earplugs while sleeping may result in more difficulty for us to wake up. As our ears get blocked to hear any noise, it makes us barely hear anything including the alarm sound.
Being that said, we need the alarm that has the high-decibel sound to break through the earplugs to wake us up. Even further, we should take the advanced ones with vibration mode to keep our bed partner or neighbor stay asleep.
Suppose that a typical earplug has 33 NRR which means able to alleviate the noise by 17 dB. Exposed to 50 dB noise will turn it to about 30-40 dB. That means we need the alarm that has more than 70 dB alarm volume to surely annoy you and wake you up.
For a greater result, the alarm volume should be more than 100dB. Many people have reported that more than 100 dB is associated as a very disturbing noise.