A hearing test is used to determine what type of auditory loss an individual is experiencing and what needs to be done to resolve the issue. The pathway from the outer ear to the brain is a complicated length of tubes, nerves, bones, and a variety of other items. Somewhere along the way, something is not right and that results in hearing loss. Doctors use various hearing test procedures to determine where the loss has occurred and if it can be fixed.
Conductive loss involves issues within the outer and middle parts of the ear. In most cases, these issues can be resolved and auditory function can be restored. For various reasons, sound waves do not make their way to the inner ear. This can be caused by problems with the ear canal, the eardrum, the bones inside the middle ear, the cavity within the middle ear, the openings into the inner part of the ear, or even the Eustachian tube.
Within the cochlea of the ear, about 30,000 nerve endings exist which help conduct sound waves to the brain through the acoustic nerve. Sensory loss refers to damage that has been done to those nerve endings, while neural loss refers to damage somewhere along the acoustic nerve. The term sensorineural hearing loss is used when damage is found in both the cochlea and the acoustic nerve. This type of damage is one of the hardest to treat. In most cases, the loss can not be medically reversed.
Central hearing loss refers to a condition where competitive sounds interfer with an individual's ability to concentrate on what they need to hear. Somewhere in the comprehension pathway, sounds that are heard translate to the actual words that were spoken. Extra noise, which can be filtered out by the average person, actually causes a problem for some individuals. For instance, they can not carry on a conversation when sitting in a busy restaurant because of all the other conversations and noise going on around them. Once the extra noise is removed, these individuals can hear just fine. Their ears work well, but their brain has trouble filtering out unnecessary noise. Currently, there's no known cure, but education on how to handle the problem effectively is helpful.
Another condition that affects an individual's comprehension is functional hearing loss. In this case, psychological or emotional problems seem to block the auditory pathway as opposed to physical damage. This type of loss is hard to diagnose with a typical hearing test because a patient responds to speech as if his ears can not hear it, but his ears may be working fine. The physician must be aware of his patient's psychological background as well as any unusual or traumatizing emotional circumstances he's going through.
Of course, any patient can also have a mixture of issues. Typically, mixed hearing loss refers to both conductive and sensorineural loss being combined. As mentioned earlier, conductive loss may be regained through known therapy measures, so this type of loss is most likely to be targeted when there's more than one known cause.