Understanding Hearing Impairment

You already know that hearing is one of the five senses that allows us to perceive sound. Hearing impairment, or hearing loss, occurs when you lose part or all of your ability to hear. Other terms that are used to refer to hearing impairment are deaf and hard of hearing.


Hearing impairments are classified in terms of the severity and type of hearing impairment. The severity of the hearing impairment is categorized based on the minimum sound that can be heard with your better ear. The higher the decibel (dB), the louder the sound.


With mild hearing impairment, the minimum sound that can be heard is between 25 and 40 dB. People at this level cannot hear soft noises and may have trouble following conversations in noisy settings.

With moderate hearing impairment, the minimum sound that can be heard is between 40 and 70 dB. People at this level cannot hear soft or moderately loud noises and may have trouble hearing unless they use a hearing aid.


With severe hearing impairment, the minimum sound that can be heard is between 70 and 95 dB. People at this level are unable to hear most noises and may rely on lip-reading and/or sign language, even with the use of a hearing aid.


With profound hearing impairment, the minimum sound heard is 95 dB and over. People at this level may only hear very loud noises and rely solely on lip-reading and/or sign language. Hearing aids are not effective.


Now, let's take a look at the types and causes of hearing impairment.


Types and Causes of Hearing Impairment

Conductive hearing loss is when a hearing impairment is due to problems in the outer ear, middle ear, ear canal, eardrum, or the ossicles, which are the tiny bones in the middle ear. When the sound is not being conducted properly through the ear, conductive hearing loss occurs. Most cases of conductive hearing loss can be corrected medically or surgically.


Causes of conductive hearing loss include:

  • Fluid in the middle ear as a result of colds

  • Otitis media, commonly referred to as ear infection

  • Poor eustachian tube function

  • Perforated eardrum

  • External otitis, commonly referred to as ear canal infection

  • Allergies

  • Earwax buildup

  • Benign tumors or having a foreign body in the ear

  • Structural abnormalities of the outer ear, ear canal, or middle ear


Sensorineural hearing loss (SNHL), also referred to as nerve hearing loss, occurs when there is damage to either the auditory nerve or the cochlea, which is the inner ear. The hearing loss in SNHL is permanent, although it may be possible to treat it with hearing aids.


Causes of SNHL include:

  • Exposure to excessively loud noise

  • Head trauma or sudden air pressure changes (e.g., during airplane descent)

  • Illnesses, such as Meniere's disease and meningitis

  • Structural abnormality of the inner ear

  • Tumors

  • Aging

  • Medication side effects (e.g., aspirin and Vicodin)

  • Autoimmune inner ear disease

  • Otosclerosis, the abnormal growth of the bone that is in the middle ear


When conductive hearing loss and SNHL occur at the same time, it is referred to as mixed hearing loss. Mixed hearing loss occurs when there is both damage to the outer or middle ear and damage to the inner ear.


Central hearing loss occurs when there are problems within the brain that interfere with the ability to interpret or understand sounds. This is the rarest type of hearing impairment and the hardest to treat.

Causes of central hearing loss include:

  • Damage to brainstem structures

  • Severe head trauma

  • Damage to the auditory nerves or the pathways that lead to them

  • Brain tumors


Functional hearing loss occurs when the functioning of the ears is normal, but the person is showing a reduced response or not responding at all to sounds. Because there are no functional hearing problems in individuals with functional hearing loss, it is the most difficult type of hearing loss to detect and the most often misdiagnosed. Functional hearing loss is caused by mental health problems, such as ADHD and depression.




Treatment depends on several factors, including:

  • The type of hearing impairment (i.e., central hearing loss versus conductive hearing loss)

  • Whether the hearing loss is reversible or permanent

  • Whether there is an underlying condition that causes the hearing loss and if the condition is treatable

  • The severity of the hearing loss (i.e., mild hearing loss versus profound hearing loss)


Once the type of hearing impairment has been determined, the first step is to recognize the cause of the hearing impairment. Once a cause has been identified, treatment options include:


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


Signaling and Text Display Systems

People with hearing loss can benefit from signaling and substitution systems, which convert sound or key strokes into another mode, such as text or flashing lights. These systems include:

  • Signaling and Warning Systems

  • Telephones

  • TV Closed Captioning

Digital Cell Phones and Hearing Aid Use

A common complaint of hearing aid users is the inability to use cell phones, particularly digital cell phones, with their hearing aids, or that they experience interference when trying to do so. Digital hearing aids are being continually updated to provide shielding from this interference. Cell phone technology also is changing. In fact, in 2003, the Federal Communications Commission (FCC) developed a report requiring a number of future actions by manufacturers and service providers to make digital wireless phones that are capable of being used effectively with hearing aids.

In the meantime, there are many strategies that will improve listening when using cell and land based telephones with hearing aids. For more information, please see Strategies for Using Your Cell Phone with Your Hearing Aids.


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. The Cochlear Implant Center at UCSF Medical Center has been involved in the development and design of cochlear implant systems for over 30 years.


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