Hearing is our first contact with the world. Inside the mother's womb, the foetus hears all the sounds within the body and also can distinguish the mother's voice. After birth when infants are laid across their mothers they quiet down. This happens because they hear their mother's familiar voice and heart beats, so they stop crying. A child's first learning comes through hearing.
Infants respond to sounds by blinking or startling.
Infants acquire information by listening. They can recognize the sounds of familiar people and objects and then they try to imitate these sounds. As children grow they develop language by listening to speech and by associating sounds to words or objects. Eventually they attach meaning to sounds and words. By the time a child reaches school age, he or she will have acquired on average 5000 words, and have 100 million meaningful connotations.