Types of Hearing Loss
Conductive Hearing Loss
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. This type of hearing loss can be temporary or permanent, and can often times be managed medically or surgically. Possible causes of conductive hearing loss:
- Fluid in the middle ear
- Ear infection
- Allergies
- Poor eustachian tube function
- Perforated eardrum
- Impacted earwax
- Presence of a foreign body
- Absence or malformation of the outer ear, ear canal, or middle ear bones (ossicles)
- Benign tumor
Sensorineural Hearing Loss (SNHL)
Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea), or the nerve pathways from the inner ear to the brain. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. SNHL reduces the ability to hear sound. Even when speech is loud enough to hear, it may still be unclear or sound muffled. Possible causes of SNHL:
- Aging
- Loud noise exposure
- Hereditary causes
- Genetic syndromes
- Drugs that are harmful to the ears (ototoxic)
- Certain illnesses
- Head trauma
- Absence or malformation of the inner ear structures or auditory nerve
Mixed Hearing Loss
Mixed hearing loss refers to when a conductive hearing loss and sensorineural hearing loss occur simultaneously. For example, there may be damage to the outer or middle ear as well as the inner ear (cochlea) or auditory nerve.
Auditory Neuropathy Spectrum Disorder (ANSD)
Auditory Neuropathy Spectrum Disorder is an auditory disorder in which the neurons in the hearing pathway do not send signals simultaneously or efficiently. As a result, a person with ANSD may have difficulty hearing and understanding speech. Severity of ANSD can vary, ranging from mild to severe auditory problems. Causes of ANSD are unknown; however, children who are born prematurely, require extended oxygen support, or have a family history of the condition are at a higher risk.
Auditory Processing Difficulties
Auditory processing disorders can impact speech and language development, academic success, and daily communication. Effects may vary based on the amount of auditory processing difficulty and whether problems other than auditory processing are present. Auditory processing problems can exist with both normal hearing and hearing loss. When hearing loss is present, it may not be possible to determine which difficulties are caused by auditory processing disorder and which are caused by the hearing loss or other factors. A comprehensive auditory processing evaluation is required to determine if a child has an auditory processing disorder.
Degrees of Hearing Loss
The outcome of a hearing evaluation is graphed on a chart called an audiogram, which records an individual’s thresholds of hearing (how soft one can hear). Loudness is measured in decibels hearing level (dB HL) and is represented on the vertical axis of the graph. Frequency (or pitch) is measured in Hertz (Hz) and is represented on the horizontal axis of the graph. Hearing test results are reported in “degree” rather than percentage of hearing loss. See below for details.
Mild Hearing Loss
Thresholds 26-40 dB HL. Individuals with mild hearing loss may complain of difficulty hearing soft speech and listening in background noise. Children with mild hearing loss may experience impacted speech and language development.
Moderate Hearing Loss
Thresholds 41-55 dB HL. Individuals with moderate hearing loss often complain of difficulty hearing conversations in quiet and background noise. Voices must be loud to be understood. Volume on the TV or radio is often raised to a higher volume for easier listening. Children with moderate hearing loss often experience difficulty with listening, comprehension, and speech and language development.
Moderately-severe Hearing Loss
Thresholds 56-70 dB HL. Speech must be loud to be understood. Volume and clarity of speech is significantly compromised. Communicating in group situations are often extremely difficult. For children, speech, language, vocabulary and comprehension are likely to be affected.
Severe Hearing Loss
Thresholds 71-90 dB HL. Normal conversation is not audible, and loud speech is difficult to hear or understand. Individuals with severe hearing loss may be able to identify environmental sounds. Speech, language, vocabulary and comprehension are significantly impacted. Visual input such as sign language is beneficial, even if amplification is used.
Profound Hearing Loss
Thresholds 91 dB HL and higher. Only very loud sounds may be heard, and even amplified speech may be soft and may not be understood. Speech, language, vocabulary and comprehension are significantly impacted. Visual input such as sign language is often relied upon, even if amplification is used.
Hearing Loss Treatment
Several options are available for hearing loss, ranging from medical treatment to listening devices, such as hearing aids. Treatment depends of the cause and severity of hearing loss. For age-related hearing loss, there is no cure, but hearing aids and other listening devices help treat the problem and improve quality of life.
Medical Treatment
Medical treatment, including medications and surgery, is recommended for many types of hearing problems, particularly conductive hearing loss. However, even if medical treatment is not necessary for your type of hearing loss, we highly recommend a visit to an audiologist for both a definite diagnosis of the type of hearing loss and treatment advice.
Some of the most common causes of conductive hearing loss are fluid in the middle ear, with or without infection, and earwax blocking the ear canal. In cases where there is a bacterial infection of the middle ear, antibiotics are often used. Although these conditions often can be diagnosed and treated by a primary care doctor, persistent problems may require the care of an ear specialist. Conductive hearing loss also may be caused by a problem with the bones of the middle ear, which, in many cases, can be treated with surgery.
Hearing Aids
If diagnosed with hearing loss that cannot be treated medically, a doctor will recommend a hearing aid evaluation and consultation with an audiologist. This consultation appointment will help determine which hearing aids or other assistive listening devices would be most appropriate. Lifestyle, listening needs and hearing concerns are important in determining the appropriate hearing aids.
Assistive Listening, Hearing Enhancement, and Alerting Devices
In some cases, hearing or alerting assistive devices may be recommended in addition to, or instead of, hearing aids. Hearing assistance technologies come in two forms:
- Signaling or Test Display Devices — These are designed to convert sound or keystrokes into visual or vibratory stimulus, or into a written text.
- Assistive Listening Devices — These instruments are designed to enhance the sound that is received by picking up the sound closer to its source. This reduces the effects of distance, noise and reverberation and transmits sound directly to the ears or hearing aids.
There are a number of devices that can assist hearing in a variety of settings. These include:
- Large Area Listening Systems
- Television Listening Systems
- Conference Microphones
- Personal FM Systems
- Amplified Telephones
Cochlear Implants
A cochlear implant is a small electronic device that can help improve the hearing of people with severe, irreversible hearing loss. Although a cochlear implant does not restore normal hearing, it can allow a person to hear and understand more speech than was possible with a hearing aid.
Aural Rehabilitation and Listening and Auditory Communication Enhancement
Unfortunately, hearing aids will not correct hearing loss or restore hearing to normal levels. However, the use of hearing aids and assistive listening devices along with auditory training can help maximize hearing abilities. Training may consists of:
- Audiologic rehabilitation classes
- Learning good listening strategies
- Establishing guidelines for communicating with those around you