A hearing test determines how well a person can hear different sounds.
Sounds are transmitted by sound waves that travel through the air and through bone. A hearing test usually determines how well a person hears sounds that are presented to the ear and to the skull bones.
Testing for sounds that travel through the air is done with a person wearing earphones over his or her ears. Pure tones of various frequencies are presented to one ear at a time at controlled volumes. The person being tested is asked to indicate when he or she first hears the sound. The softest sounds that the person can detect are recorded for each frequency. The results are put on a graph and compared to a normal hearing graph, called an audiogram.
To test for sounds that travel through the bone, tuning forks of different frequencies can be tapped and held against a person's skull. Sounds can also be produced against the skull by other methods though the principle is the same. The person being tested is asked to indicate which sounds he or she can detect.
No special preparation is required for a hearing test.
The loudness of sound is measured in units called decibels (dB). A soft sound, such as normal conversational speech, ranges from about 25 to 35 dB. A loud sound, such as a jet plane taking off nearby, is about 180 dB. Loud music, such as at a rock concert, can reach 80 to 120 dB. Sounds louder than 85 dB can cause hearing loss.
A person with normal hearing can detect low tones (frequencies of 64 cycles per second, abbreviated as cps, or Hz) at 30 to 40 dB and high tones (around 11,500 Hz) at 10-20 dB. Most tones in between these extremes can be heard at less than 10 dB. Human hearing is most sensitive between 500 and 3000 Hz, which is the predominant frequency range of human speech. If a person cannot detect pure tones in this range below 10-20 dB, some hearing loss may be present.
Conditions that may lead to hearing loss are: acoustic neuroma, a non-cancerous growth of the acoustic nerve in the ear canalacoustic trauma, hearing loss caused by loud noise that occurs slowly over time, often as the result of loud noise in an industrial workplace environmentage-related hearing loss (some hearing loss is a natural consequence of aging)Alport's syndrome, a genetic disorder that consists of nerve-related deafness and kidney problemslabyrinthitis, an inflammation of the inner ear canalsMeniere's disease, a disease of the inner ear that causes dizziness, ringing in the ear, and nerve-related deafnessotosclerosis, which is abnormal bone formation in the inner earruptured or perforated eardrum