Secrets Contained in Mom’s Voice


A video about a baby, who was born profoundly deaf, hearing her mom’s voice for the first time and being almost moved to tears, went viral. Hearing her mom’s soft voice for the first time with the help of special hearing aids, the baby smiled and also pouted almost in tears. Does she remember her mom’s voice that she heard in the womb?

Fetuses can hear

Until the end of the 19th century, people thought fetuses don’t have a hearing ability. However, in 1925, it was proven that fetuses cana hear as Albrecht Peiper, a German doctor, discovered that fetuses respond to a car horn.

By week 4 of pregnancy, the parts where ears are going to be formed begin to show on an embryo, and the inner ear1 is completed by week 24. The nervous system starts developing in the beginning fetal stage, and by week 34 a fetus has the auditory nerve, comparable with that of a newborn.

1. Inner ear: the innermost part of the ear. The inner ear is made of three parts: the cochlea which is the auditory area, the semicircular canals and the vestibule which sense balance.

While being in the mom’s womb for nine months, a fetus is exposed to various kinds of noises made inside the mom’s body such as her heartbeat, bowel movement, and blood flow. The fetus can also hear their own heartbeat which is about twice faster than their mom’s, and the sound of their fetal movement. The fetus also hears the noises from the outside such as cars and music while growing up.

When newborn babies get startled and cry, static sound from a blank channel on TV calms them down and they stop crying quickly. Some parents say that vacuum cleaner sound calm their babies down, and some say that the rustling sound of a plastic bag made their babies smile again. This is because while the noises from the outside pass through the mom’s uterine walls and amniotic fluid, quiet noises or high-pitched sounds are filtered and only constant low-pitched sounds in low frequency are delivered to the fetus. Due to these experiences inside the womb, babies are more accustomed to low sounds.

Hearing and fetal brain development

Intelligence is determined, depending on how elaborately synapses develop to connect neurons in the brain. In about the sixth month of pregnancy, the fetal brain’s development speeds up to where about 60 million brain cells are made every day. Over 80% of the fetal brain is already completed, and the fetus can hear noises from outside of the womb. And by the eighth month of pregnancy, short-term memories begin to be formed, and the fetus can distinguish the intensity of sounds. They can even tell what mood their mom is in by distinguishing the intensity of the mom’s voice. Like this, among the five senses, hearing develops most in the womb before birth, and it is closely related to the fetal brain development.

Scientists say that a fetus’ various sensational stimulations that they see, hear, and feel provide energy for the growth of the brain cells. Among them, stimulations from hearing take up over 80% of all, and sounds or music influence the development of a fetus’ body and intelligence, not only emotional development. The noises that a fetus experiences inside the womb become the first stimulation that influences the brain cells through the fetal auditory organ, and the noises that enter the fetal brain are clearly engraved in their memories.

The noise a fetus hears most in the womb is their mom’s heartbeat. Dr. William Liley at Auckland University in New Zealand had an interesting experiment by using a metronome. When the subjects were given a metronome and asked to set it at the beat that they like, amazingly most people set it at 50 to 90 times per minute. This almost matches human heartbeat rate.

The reason a crying baby stops crying when placed on their mom’s chest is because of the heartbeat of the mom that he hears through her chest. This is a familiar noise that he constantly heard in the womb. On top of this, if the baby hears the mom’s voice singing a lullaby, he finds comfort even more easily.

Among many factors that stimulate hearing, what a fetus likes the most is the mom’s voice. The mom’s calm voice is a good stimulus that develops the fetus’ synapses. Newborn babies who cannot even open their eyes yet show response toward the direction where their mom’s voice is heard, because they remember the voice that they heard while they were in the womb. If they also constantly heard the dad’s voice while they were in the womb, they will show response to their dad’s voice, too.

Babies grow by bonding with mom

In 2016, the researchers of Stanford Medical School analyzed MRIs of 24 children between ages 7 and 12 to see which part of the brain becomes active when they hear their mom’s voice. The research team recorded their mom’s voice and the voices of unfamiliar women of the same age range, and had the children listen to them. For objectivity, they had the narrators say random words other than their children’s names. As a result, 97% of the children recognized their mom’s voice in one second.

The part of the brain that became most active when they heard their mom’s voice was the primary auditory cortex and the prefrontal cortex. When the primary auditory cortex is stimulated, abilities such as emotions, social skills, and face recognition improve. The prefrontal cortex is a brain region that recognizes changes in surroundings, which helps react to the surrounding sounds and take in new information. Also, the prefrontal cortex is known to contribute to the improvement of self-control by controlling reason. The study lead author, PhD Daniel Abrams, said, “Increasing the time spent with the mom can help improve communication skills and social skills.”

Mom’s voice accelerated the secretion of hormones that give emotional stabilization. Seth Pollak, Professor of Psychology at the University of Wisconsin–Madison, put 61 girls between 7 and 12 years of age in a stressful situation where they had to solve math problems, divided them into three groups, and had an experiment. The first group had a face-to-face talk with their moms for about 15 minutes; the second group watched a movie for 60 minutes after having a talk on the phone with their moms for about 15 minutes; and the third group just watched a movie for 75 minutes without any contact with their moms. Then, he watched the changes of cortisols which respond to stress and the changes of oxytocins which make one feel happy.

As a result of the experiment, there was a distinctive difference between the children who had conversation with their mom directly or indirectly and those who didn’t. As for the children who heard their mom’ voice, the secretion of cortisols decreased rapidly within 30 minutes after the exam, and the amount of the secretion of oxytocins maintained for one hour. As for the children who watched a movie without having talked with their mom, the amount of secretion of the hormones stayed the same as they were stressed. This shows that even just talking with mom without physical contact decreased the level of stress. To children, their mom’s voice gives more comfort than anything else.

Babies clearly remember the soft voices of their moms that they heard in the womb. And they grow up, hearing the soft voices. The power and strength contained in the mom’s voice is truly amazing and mysterious. The mom’s voice, which was always there for the child from the beginning of their life, contains the mom’s love which only the child can feel and be comforted by.

“For you will nurse and be satisfied at her comforting breasts; you will drink deeply and delight in her overflowing abundance.” … “As a mother comforts her child, so will I comfort you; and you will be comforted over Jerusalem.” Isa 66:11–13

“My sheep listen to my voice; I know them, and they follow me.” Jn 10:27

“Fetal Communication” by Jeong Gyeong-hee and Park Hyo-mi, Communication Books, 2014
“A Calm Voice is Good for Fetus” by Seo Yu-heon, Donga Ilbo, 2000