AUDIOMETRY

Audiometry

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.

How the Test is Performed

• Pure tone testing (audiogram) -- For this test, you wear earphones attached to the audiometer. Pure tones of a specific frequency and volume 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.
• Tympanometry -- A measure of the vibration of the ear drum and middle ear pressure.

Why the Test is Performed

This test can detect hearing loss at an early stage. It may also be used when you have hearing problems from any cause.

The following conditions may affect test results:

• Acoustic neuroma
• Acoustic trauma from a very loud or intense blast sound
• Age-related hearing loss
• Alport syndrome
• Chronic ear infections