If you’ve ever wondered what’s up with singing to pregnant bellies or how much language newborns understand, here are six questions and answers about fetal hearing that you might find interesting.
#1: When can a human fetus start to hear? Generally, human fetuses can probably hear as early as 16 weeks gestation, when their inner ear structures are fully formed and operational! Researchers have seen the first indications that fetuses are regularly interacting with or responding to external auditory stimuli at 23 weeks. (source)
#2. What can they hear? Human fetuses seem to respond first to lower-frequency sounds (deep humming, or a stomach growling) and later to higher-frequency sounds. So if you aren’t sure if they can hear you yet, start off with talking low or singing just the first part of “The Lion Sleeps Tonight.” (source)
#3. What if they can’t hear? Sounds are just waves of vibration, so Deaf human fetuses can still feel you talking or singing to them! (cool article about feeling songs here)
#4. How loud is a song for a human fetus? Typical background noise in utero is 28 decibels or so. When the pregnant person sings, that song is around 84 decibels in utero. (source) For context, a whisper is about 30 decibels, and an alarm clock comes in around 80. (source)
#5. Can human fetuses who can hear understand that some sounds are different than others? They sure can! By 36 weeks old, and sometimes as early as 27 weeks old, they not only recognize a difference between vowels and consonants; they actually respond differently to them. (source)
#6. And can they understand that some voices are different than others? Yes. At term (38 weeks), human fetuses who can hear can distinguish a mother’s voice from a strange female voice. (source)
Got a question about another aspect of fetal hearing? Comment below!