Sounds and vibrations are felt by babies in utero and by 16 weeks they can hear.
Babies start to listen reactively from as early as 16 weeks although the development of the ear is not complete until 24 weeks. By the third trimester, a baby will turn his/her head towards a sound. This means that by the time a baby is born it has been exposed to music, familiar sounds and language patterns.
The first sounds a baby hears
Because the vibrations from the mother’s voice travel through her body to the womb, a baby is more receptive to his/her mother’s voice as it is louder than noises from the outside world. Between 20 -24 weeks a baby begins to recognise the deeper tones of his/her father’s voice.
The affect of sound on the baby in the womb
Researchers at the University of Helsinki, Finland studied 33 pregnant mothers and their babies. From week 29 until birth, 17 mothers listened to a CD with two, four minute sequences of made-up words (“tatata” or “tatota”, said several different ways and with different pitches).
After birth, the researchers tested the hearing of all 33 babies and performed an EEG (electroencephalograph) brain scan to see if the newborns responded differently to the pseudo words and different pitches. The brain activity of the babies who listened to the CD in utero increased when those words were played, while babies who did not hear the CD in the womb did not react as much.
Stimulating your baby
You can start stimulating your unborn baby by reading aloud and playing music. This helps to develop early communication skills. Infants respond well to music as the lilting melody combined with words, pitch, intonation and phrasing help the baby to learn.
Be careful not to damage your baby’s ears
Headphones should never be placed directly on the pregnant belly because the frequencies can damage or destroy the hair cells in the unborn baby’s ear. 
Listening starts in the womb. If you are worried about your baby’s hearing it is important to have it checked by a hearing professional.
 Shahidullah S and Hepper PG (1992) ‘Hearing in the foetus: pre-natal detection of deafness’ International Journal of Prenatal and Perinatal Studies 4(3/4):235-240
 Minna Huotilainen, Ph.D., docent, Finnish Center of Excellence in Interdisciplinary Music Research, University of Helsinki, Finland
 Graven SN and Browne JV (2008) ‘Auditory development in the foetus and infant’ Newborn Infant and Nursing reviews