Audiometry: The Basics

Introduction

Let’s get to know the meaning of audiometry.

Hearing loss becomes more common as we age though it can occur in younger people. The American Family Physician conducted a study and it was seen that about 25 percent of those above the age of 50 experienced hearing loss while 50 percent of those above the age of 80 experienced it too. Audiometry is a test which checks for hearing loss.

This examination tests the functionality of the ear. It particularly checks the intensity and tone of sounds, balance issues, and any other problem related to the functionality of the inner ear. It is administered by an audiologist, a doctor skilled in diagnosing and treating hearing loss.

Sound intensity is measured in units called decibels (dB). A healthy ear hears quiet sounds such as whispers and these are about 20dB. The threshold limit value for sound, that is, the loudest permissible range of sound intensity without any harmful effects is about 85dB. A loud sound such as that emanating from a jet engine is between 140 to 180dB. The sound tone is measured in cycles per second and the unit is Hertz (Hz). Humans hear tones between 20 to 20,000Hz and the speech of humans fall within the tone range of 500 to 3,000 Hz. Low bass tones measure about 50 Hz.

Why is an audiometry performed?

This test is carried out to know how well one can hear. It can be done routinely or when there is a noticeable hearing loss.

Common causes of hearing loss include:

• Birth defects
• Chronic ear infections
• Genetic conditions such as otosclerosis, a condition characterized by abnormal bone growth which prevents structures inside the ear from functioning properly
• Ear trauma
• Diseases of the inner ear such as Meniere’s disease or an autoimmune disease that affects the inner ear
• Frequent exposures to loud noises
• Ruptured eardrum

Ear injury or frequent exposures to loud noises for a long time can cause hearing loss. Sounds louder than 85dB, such as that heard at a rock concert, can cause hearing loss after just a few hours. It is beneficial to use hearing protection, like foam earplugs, if you frequently get exposed to loud music or industrial noise.

Sensorineural hearing loss also referred to as permanent hearing loss happens when the hair cells in the cochlea are not functioning properly. The cochlea is an ear part responsible for translating sound vibrations into nerve impulses that are sent to the brain. Sensorineural hearing loss also occurs when the vestibulocochlear nerve (which carries sound information to the brain) is damaged or there is damage to the brain part responsible for processing this information. Sensorineural hearing loss can either be mild, moderate or severe.

Risks involved

Audiometry carries no risk as it is non-invasive.

PREPARING FOR AUDIOMETRY

No special preparations are required for audiometry. All you have to do is to keep to your appointment and follow the instructions of the audiologist.

Audiometry Procedure

Few tests are involved in audiometry. A pure tone test is done and this measures the quietest sound you can hear at different pitches. An audiometer is used for this test and this machine plays sounds via headphones. The audiologist or the assistant will play sounds of varying tones and speech, at different spacing into one ear at a time, to know your hearing range. They will give you instructions for each sound such as raising your hand when a sound becomes audible.

Another test done is that which will help the audiologist to check your ability to differentiate speech from background noise. A sound sample is played and one is asked to repeat the words heard. The ability to recognize words can be helpful in diagnosing hearing loss.

Furthermore, a tuning fork can be used to determine how well you hear vibrations through your ears. The audiologist puts this metal device against the mastoid, the bone behind the ear, or makes use of a bone oscillator to check how well the vibrations move from the bone to the inner ear. A bone oscillator is a mechanical device that transmits vibrations as a tuning fork would.

This test is painless, not discomforting and takes about an hour.

What is done after an audiometry?

Following audiometry, the audiologist reviews the results and advises based on your result. Preventive measures may be needed such as wearing earplugs when in contact with loud noises, or any corrective measures that may be helpful such as wearing a hearing aid.