@ancientgran
By googling "babies know mothers voice"
I found this
www.babycenter.com/baby/baby-development/baby-sensory-development-hearing_6509
And this
parentingscience.com/how-do-children-respond-to-a-mothers-voice/
And this
www.pnas.org/content/112/10/3152
This will further explain auditory function and differentiation in foetuses awareness of male and female voices as well as explain how babies know their mother's face before they learn others at around 3 months and how they can differentiate between females.
"Researchers have found that babies are able to discriminate between their mother’s odors and odors produced by either unfamiliar lactating females and females who have never given birth. Newborns begin to prefer their mother’s odors, and this familiar scent may even help calm or soothe your infant."
"Studies have shown that by three months of age your baby can discriminate between their mother’s face and the face of a stranger. As with your voices, with more experience your baby will develop a preference for your faces and those around you. "
babyschool.yale.edu/does-my-baby-recognize-me/
You can find more about how a mothers diet affects a baby, such as if she regularly eats spicy food and how that influences their palette as they start eating solids through her breastmilk.
Babies are really quite clever, have you heard about 'breast crawl'? There is much we can learn about pregnancy and what is termed the Fourth Trimester from studies. Google is your friend, you may find the book The Primal Wound interesting as well as John Bowlby's work.