Hearing loss can be experienced in varying degrees, such as mild, moderate, moderately-severe, severe or profound. Additionally, this loss can also vary depending on frequencies, or pitches. A series of hearing tests can determine the amount of loss you experience.
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 0-25 dB across the range of frequencies tested. Speech testing is also conducted as a part of this series of evaluations and helps to assess your ability to hear words clearly. These tests can help determine the type of hearing loss you’re experiencing, which can be categorized conductive, sensorineural or mixed.
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 (pinna or ear canal), eardrum (tympanic membrane) or the 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 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. This abnormality prevents sound from being transmitted to the brain normally, resulting in a hearing loss.
The hair cells may have been abnormal since birth (congenital), damaged as a result of genetics, infection, drugs, trauma or exposure to damaging noise. Hair cells may also become damaged as a result of the aging process, a kind of 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. The most commonly recommended treatment option for hearing loss is hearing aids, however cochlear implants are recommended in the most severe cases.
Individuals with sensorineural hearing loss may report muffled speech, ringing in the ears (tinnitus), difficulty hearing in background noise or that others do not speak clearly.
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 in addition to a recommendation of hearing aids.