Audiometry: A Review of the Implementation and Evaluation

An audiometry exam tests your ability to hear sounds. Sounds vary, based on their loudness (intensity) and the speed of sound wave vibrations (tone).

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 ear canal, eardrum, and 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):

• A whisper is about 20 dB.
• Loud music (some concerts) is around 80 to 120 dB.
• A jet engine is about 140 to 180 dB.

Sounds greater than 85 dB can cause hearing loss after a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time.

The TONE of sound is measured in cycles per second (cps) or Hertz:

• Low bass tones range around 50 to 60 Hz.
• Shrill, high-pitched tones range around 10,000 Hz or higher.

The normal range of human hearing is about 20 to 20,000 Hz. Some animals can hear up to 50,000 Hz. Human speech is usually 500 to 3,000 Hz.

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How the Test is Performed?

Your health care provider may test your hearing with simple tests that can be done in the office. These may include completing a questionnaire and listening to whispered voices, tuning forks, or tones from an ear examination scope.

A specialized tuning fork test can help determine the type of hearing loss. The tuning fork is tapped and held in the air on each side of the head to test the ability to hear by air conduction. It is tapped and placed against the bone behind each ear (mastoid bone) to test bone conduction.

A formal hearing testing can give a more exact measure of hearing. Several tests may be done:

• Pure tone testing (audiogram) -- For this test, you wear earphones attached to the audiometer. Pure tones are delivered to one ear at a time. You are asked to signal when you hear a sound. The minimum volume required to hear each tone is graphed. A device called a bone oscillator is placed against the mastoid bone to test bone conduction.
• Speech audiometry -- This tests your ability to detect and repeat spoken words at different volumes heard through a head set.
• Immittance audiometry -- This test measures the function of the ear drum and the flow of sound through the middle ear. A probe is inserted into the ear and air is pumped through it to change the pressure within the ear as tones are produced. A microphone monitors how well sound is conducted within the ear under different pressures.
  

The Medical Audiometer Devices operating in the across the globe includes Benson Medical Instruments, Hedera Biomedics Srl, Smart Diagnostic Devices, Resonance, William Demant Holding A/S, Natus Medical Incorporated, Inventis Srl, Auditdata, Medrx, And Interacoustics A/S. Among Others

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Reference:

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