Hearing tests are usually carried out in an environment which is soundproofed from external noise. The person whose hearing is being tested listens to sounds transmitted by an audiologist and presses a button to signal when they have heard something. The results of the test are plotted on an audiogram.
Audiogram – measuring loudness and pitch
Volume The vertical axis represents volume (loudness) which is measured in decibels (dB). Sounds become louder from the top down – softest near the top of the graph.
Pitch The horizontal axis represents frequency (pitch) which is measured in hertz (Hz). Pitch goes from low (125Hz) on the left to high (8000Hz) on the right – similar to a piano (low notes on the left, higher to the right).
0 dB does not mean that there is no sound at all. It is simply the softest sound that a person with normal hearing ability would be able to detect at least 50% of the time. Normal conversational speech is about 45 dB.