Through her normal hearing she caught the beginning of a shriek, then silence.
Some babies may seem to have normal hearing, but they develop a problem processing sounds.
Those with normal hearing can use visual clues to assist during the listening process.
And normal hearing is very important when a young child is learning to talk.
Young friends with normal hearing were brought in to join his classes at home, and everybody made progress - learning was contagious.
Using up to 1600 females with normal or damaged hearing, he was able to work out how they did this.
It is not the same as normal hearing, but it can help them learn to speak.
His parents have normal hearing, but their three sons do not.
Four of the members are deaf, one has normal hearing.
Each species has a range of normal hearing for both amplitude and frequency.