Audiometry
What is the Audiometry
This test tests your ability to hear sounds. Sounds vary according to the volume or strength (intensity) and the speed of vibration of sound waves (pitch).
Hearing occurs when sound waves stimulate the nerves of the inner ear. The sound then travels along nerve pathways to the brain.
Sound waves can travel to the inner ear through the external auditory meatus, the eardrum and the bones of the middle ear (air conduction). They can also pass through the bones around and behind the ear (bone conduction).
The INTENSITY of sound is measured in decibels (dB):
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A whisper is about 20 dB.
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Loud music (some concerts) is around 80 to 120 dB.
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A jet engine is about 140 to 180 dB.
Sounds over 85 dB can cause hearing loss after a few hours. Louder sounds can cause immediate pain, and hearing loss can occur in a very short time.
The PITCH of sound is measured in cycles per second (cps) or Hertz:
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The bass tones of a bass fluctuate between 50 to 60 Hz.
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The highest elevation treble tones are approximately 10,000 Hz or higher.
The normal range of hearing for humans is approximately 20 to 20,000 Hz. Some animals can hear up to 50,000 Hz. Human speech is generally between 500 and 3,000 Hz.
How the test is performed
Your doctor can test your hearing with simple tests that can be done in his office. These may include getting a questionnaire and listening to whispers, tuning forks, or tones from an otoscope.
A specialized tuning fork exam can determine the type of hearing loss. The tuning fork is struck and held in the air on each side of the head to test air conduction hearing. It is tapped and placed against the bone behind each ear (mastoid bone) to test bone conduction.
Exam Preparation
Download here the instructions
What it feels like during the exam
This test does not cause any discomfort and its duration varies. The initial evaluation can take 5 to 10 minutes, while a detailed audiometry can take nearly an hour.
Reasons for Testing
This test can detect hearing loss at an early stage. It can be used when you have hearing problems of any kind.
Normal results
Normal results include:
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The ability to hear a whisper, normal speech, and the ticking of a clock is normal.
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The ability to hear a tuning fork through air and bone is normal.
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On detailed audiometry, hearing is normal if one can hear tones from 250 to 8000 Hz at 25dB or less.
What Abnormal Results Mean
There are many types and degrees of hearing loss. In some types, only the ability to hear high or low tones is lost, or only air or bone conduction is lost. The inability to hear pure tones below 25 dB indicates some degree of hearing loss.
The extent and type of hearing loss can give clues to the cause and the chances of hearing recovery.
The following diseases can affect test results:
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acoustic neuroma
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Acoustic trauma caused by a very loud or intense bang or sound
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age-related hearing loss
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Alport's syndrome
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Chronic ear infections
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labyrinthitis
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Meniere's disease
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Permanent exposure to loud noises, such as from work or listening to music
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Abnormal growth of the middle ear bone, called otosclerosis
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perforation or rupture of the eardrum
risks
There is no risk.
Considerations
Other tests may be done to check the function of the pathways in the inner ear and in the brain. One of these is the evaluation of otoacoustic emissions (OAE), which detects the sounds emitted by the inner ear in response to sound. This test is usually done as part of newborn screening. An MRI of the head may be done to diagnose hearing loss caused by an acoustic neuroma.
Alternative names
Audiometry; Hearing test; Audiography (audiogram)
