An audiogram is a chart used to represent a person’s hearing ability and is determined by a hearing test. Audiologists use an audiogram to help determine hearing loss and the type of it. It is basically a test of ones hearing abilities. It is measured by an audiometer. In the chart there is a Y and an X axis. The Y represents the intensity of decibels and the X represents the frequency which is measured in Hertz. People measuring the hearing have the normal standard of hearing as a way to compare. As already mentioned, hearing is measured in Hertz. The normal hearing for a person is between 250kHz to 8kHz. It is considered as average normal hearing. Hearing thresholds of humans and other mammals can be found by using behavioural hearing tests or physiological tests. An audiogram can be obtained using a behavioural hearing test called Audiometry. For humans the test involves different tones being presented at a specific frequency (pitch) and intensity (loudness). When the person hears the sound they raise their hand or press a button so that the tester knows that they have heard it. The lowest intensity sound they can hear is recorded. The test varies for children, their response to the sound can be a head turn or using a toy. The child learns what they can do when they hear the sound, for example they are taught that when they heard the sound they can put a toy man in a boat. A similar technique can be used when testing some animals but instead of a toy, food can be used as a reward for responding to the sound. Physiological tests do not need the patient to respond (Katz 2002). For example when performing the brainstem auditory evoked potentials the patient’s brainstem responses are being measured when a sound is played into their ear. In the US, the NIOSH recommends that people who are regularly exposed to hazardous noise have their hearing tested once a year, or every three years otherwise.