Your baby will have his hearing function developed in the womb itself. By the time he is born, he is capable of paying close attention to voices, respond to familiar sounds and get startled at loud unexpected noises. However, he is not yet ready to locate the source of sound. But your baby can totally respond to rattles and bell sounds.
What you need to know
It is normal if your baby is in sound sleep and not responding to the telephone ringing and people talking in loud voices. At times, he might miss a loud noise because he is distracted or too tired. Remember, this is normal. However, consult a doctor right away if you notice any warning sign of hearing problems. A few warning signs are not changing expression at the sound of a voice or loud noise even when it is quiet, not enjoying playing with a rattle, ringing bell, or other noisemakers, and not moving his head or eyes towards a sound. Hearing tests can be conducted to evaluate if there is a hearing problem or extent of hearing problem if any.
In normal cases, rattles and bells help develop many new skills. Moving the rattle or bell from side-to-side helps babies to visually track a moving object. As their fine motor skills develop, they learn to hold the rattle or bell with a tight grasp. Sometimes, these toys particularly the rattle can double up as teether for the baby.