MODEL RELEASED. Hearing test. A young boy wearing headphones undergoing a hearing test. The machine on the right is called an audiometer. It is designed to produce sounds of varying pitch and loudness in one ear at a time. The sounds decrease in volume until they become inaudible. The person being tested responds each time they hear a sound by making a signal (such as raising the hand). Hearing tests are performed as part of a routine assessment of child development. This type of hearing test, called pure-tone audiometry, is often used to assess the extent of a person's hearing loss and to investigate possible causes.