Hearing tests (audiometry)
Hearing tests (audiometry or audiometric tests) are done to determine how loud a sound needs to be at different frequencies for you to hear it. This is known as your hearing threshold. Audiometry also isolates the softest sound you are able to hear.
The audiogram: showing hearing test results
Results of hearing tests are shown on a graph called an audiogram. The audiogram shows the type, degree, and configuration of hearing loss.
Two types of tests
There are two different types of audiometric tests that can build an audiogram. Your audiologist may recommend:
Air conduction testing. A hearing test conducted with headphones or a speaker that passes sound to the ear canal through the middle ear to reach the inner ear. This hearing test determines how your entire hearing system responds to sound, also known as your air conduction threshold.
Bone conduction testing. After an air conduction test has shown hearing loss, bone conduction testing is done. A bone vibrator is put behind the ear to send sounds straight to the inner ear and the bones of the head without going through the eardrum or middle ear. This can help your doctor evaluate which part of the ear the hearing loss is coming from.
An audiologist – the doctor performing the audiometric testing – will note how loud each sound was, and at what frequency. This builds the audiogram graph to show your hearing level and hearing ability.
Types of hearing loss measured
Based on audiometry results, the type and severity of hearing loss can be determined.
Conductive hearing loss
Conductive hearing loss occurs when sound does not pass properly through the outer ear to the middle ear bones. Conductive hearing loss makes sounds softer and harder to hear, but often can be corrected.
If you have conductive hearing loss, you will likely have abnormal air conduction test results but normal bone conduction test results. Common causes of conductive loss include:
- Ear infections.
- Excess ear wax.
- Fluid in the middle ear.
- Hole in the eardrum.
- Malformed ear canal or outer or middle ear.
- Obstruction inside the ear.
- Swimmer’s ear.
Sensorineural hearing loss
Sensorineural hearing loss, or SNHL, happens when sound moves through the outer and middle ear normally but isn’t transmitted properly through the inner ear. It is characterized by unclear normal sounds and the inability to hear faint sounds.
Having the same hearing levels from a bone and air conduction exam is the key indicator of this kind of hearing loss. SNHL is usually caused by damage to the cochlea or the nerves that connect to the brain, and it is often permanent. Common causes include:
- Drugs that damage hearing.
- Genetic or hereditary hearing loss passed on from your family.
- Head trauma.
- Malformed inner ear.
- Noise-induced hearing loss.
Descriptions of hearing loss
- Unilateral hearing loss (UHL), when one ear is normal but the other is not. It can range from mild to profound hearing loss in either the left or right ear, and it affects nearly 3% of school children in the U.S.
- Mixed hearing loss, a problem in your outer or middle ear and in your inner ear, caused by both conductive and sensorineural hearing loss.
- Symmetrical hearing loss indicates that the degree and configuration of hearing loss is the same for both your left and right ear.
- Hidden hearing loss, resulting from an issue with the brain signals rather than the ears or bones. This kind of hearing loss isn’t detected in standard hearing tests.