About Hearing Loss
Hearing loss is rarely described as a percent these days. Instead the hearing loss profile can be described in varying degrees, such as mild, moderate, moderately-severe, severe or profound. Additionally, a loss can also vary depending on what pitches or frequencies (i.e. shape or configuration) are diminished. A series of hearing tests looking at each part of the ear can determine the amount of loss you experience compared to an average of many other adult listeners with typical hearing.
The volume of sounds you hear is measured in decibels (dB), 15-20 dB being the softest whisper and 120 dB being a jet engine. The softest sounds one can hear are called thresholds. "Normal" hearing thresholds for adults are considered 0-20 dB across the range of frequencies tested (0-15 dB for children). Speech testing is also conducted as a part of this series of evaluations and helps to assess the levels of particular words you can hear clearly as well as assessing how your hearing sensitivity effects the central auditory system where speech is interpreted in the brain. These tests determine a clear diagnosis type of hearing loss and therefore help guide Audiologists in recommending an appropriate treatment plan if necessary.
Conductive hearing loss
Conductive hearing loss occurs when there is a problem with the way sound is conducted to the inner ear or cochlea. The problem may lie in the outer ear (pinnae, ear canal), eardrum (tympanic membrane) or the middle ear (middle ear ossicles and Eustachian tube). The inner ear and auditory nerve remain unaffected in this type of hearing loss.
Some causes of conductive hearing loss can include outer or middle ear infections, complete earwax blockage, deterioration of the middle ear bones (ossicles), fixation of the ossicles (otosclerosis), a hole in the tympanic membrane or absence of the outer ear or middle ear structures.
Conductive hearing losses may be temporary or permanent, depending on the source of the problem. Medical management can correct some cases of conductive hearing loss, while amplification (hearing aids) may be a recommended treatment option in more long-standing or permanent cases.
Individuals with conductive hearing loss may report that sounds are muffled or quiet. Generally, when sounds are made louder, these individuals can hear well again.
Sensorineural hearing loss
Sensorineural hearing loss occurs when there is a problem with the sensory receptors of the hearing system, specifically in the cochlea or auditory nerve of the inner ear. The majority of sensorineural hearing loss occurs as a result of an abnormality or damage to the hair cells in the cochlea, resulting in long-term changes to the auditory nerve and cortex (hence sensoriNEURAL). This abnormality prevents sound from being transmitted to the brain normally, resulting in a hearing loss that's both a loss of volume and clarity.
Damage to the hair cells may have been since birth (congenital); or as a result of genetics, infection, drugs, chronic illness, trauma or over-exposure to noise (late-onset or acquired). Regardless of all external factors increasing the severity of sensorineural hearing loss over time, long-term permanent damage for many will simply be a result of the aging process, hearing loss known as presbycusis.
Sensorineural hearing losses are generally permanent and some remain stable over time while others worsen. Therefore, routine hearing tests are needed to monitor the hearing loss just as we monitor our vision or other areas of health. Treatment options, including hearing aids or cochlear implants (in the most severe cases where hearing aids no longer help), are common recommendations.
Individuals with sensorineural hearing loss may report muffled speech, ringing in the ears (tinnitus), difficulty hearing in background noise, and claiming that others do not speak clearly.
Mixed hearing loss
Mixed hearing loss occurs when a person has a sensorineural hearing loss in combination with a conductive hearing loss. It is, very literally, a mix of sensorineural and conductive hearing losses. This means there is a problem in the inner ear as well as in the outer or middle ear. The conductive hearing loss may be temporary or permanent, depending on the source of the problem.
Mixed hearing loss can sometimes be treated with medical management and hearing aids are a common treatment recommendation.