Humans, like other mammals, are tuned to the frequencies of voices and vocalizations of people they care about, with babies being particularly attuned to their mother's voice even in the womb.

“There's very good evidence to support the fact that we are tuned to the frequencies of voices and vocalizations of people that we care about. It's not just true in rodents and in birds and other mammals, it's definitely true in humans as well. And babies are very tuned in to the sound of their mother's voice, even, yes, while they're in the womb.”