Could've sworn I'd already posted on this thread but can't find it so here goes.
My mother has, all her life, heard her mother's voice calling her to get up in the morning. Not every day, just when she was oversleeping or the alarm was set wrongly or wound down or whatever. She'll hear 'Jean! Jean! Get up!'
The voice wakes her, or rouses her if she's dozing.
This happened when she was a schoolgirl and later when she was going to work, and even when she had children of her own to get up for school.
Her mother was alive until nearly 20 years ago but her death made no difference. Mother still hears her voice now and then before she's fully awake.
It's her own subconscious cleverly waking her up with her mother's voice. It seems we can play tricks like that on ourselves.