This picture shows a graph with hearing levels of left and right ears. The left ear readings are depicted in blue whilst the right is in red. Pure tone are given to patient's right and left ears separately via head phones and response is plotted on a graph. This is called pure tone audiogram. Patient has to understand the technician's instructions to get reliable results. Therefore we need different methods to test children and mentally retarded adults. This test is done very frequently in ENT clinics. It takes about half an hour to do the test.An audiometer is required to generate the pure tones. This test is done in a sound proof environment as the background noise may interfere the test results.