My three-month-old daughter seems overly sensitive to sound. She can be sleeping deeply and something can drop nearby and she’ll scream at the top of her lungs. If, however, I’ve left a TV running, she seems to sleep through that constant noise, but if the house is too quiet the littlest thing sets her off. Is this normal? Heidi D, Barrie, ON
The short answer is, yes, this is likely normal. First, you can be reassured that she is indeed hearing when she responds to a sudden loud noise. What you are describing is likely a startle response, which is the reaction to a sudden and unexpected stimulus. In this case, it is the loud bang of a dropped object. Reactions in a startle response include physical movement away from the stimulus. Babies, who cannot always move away, will contract their arms and legs, blinking and, as your baby exhibits, crying.
With the constant hum of the television as background noise, there is no startle response.
There is a condition called hyperacusis, which is abnormal discomfort caused by sounds that are usually tolerable to people with normal hearing. It is something that is experienced subjectively, which means that it cannot be measured. While hyperacusis is described in children, it is not typically seen in infants. I think that it is unlikely there is any abnormal reason that your daughter responds to sudden loud noises this way. I would discuss this with your doctor making sure she is growing normally and has normal developmental milestones. If there is continued concern, she can be assessed by an audiologist and ear, nose and throat physician.