Hearing Loss

To understand hearing loss and your treatments options, it is important to first be familiar with normal hearing.

Normal Hearing
For sound to be heard, the ear needs to convey the message to the brain. The ear consists of four main parts: outer, middle, and inner ear and the hearing nerve. Each of these parts plays a key role in sound transmission to the brain.

Click here to enlarge image>>

The Outer Ear (or pinna) captures sound and then directs the sound down the ear canal to the eardrum. Sound vibrates the eardrum and is transmitted to the middle ear. The Middle Ear has three bones, the malleus (hammer), incus (anvil) and stapes (stirrup) that help convey sound to the inner ear. The Inner Ear (or cochlea) consists of sensory cells that convert pitch and loudness of sound into an electrical code that the Hearing Nerve (or auditory nerve) transmits to the brain.

When the ear mechanisms work properly, the ear can detect a range of pitches or “frequencies” over a wide range of loudness or “intensity.” Frequency is measured in Hertz (Hz) and intensity in decibels (dB). Normal hearing persons can detect very soft sounds of 20 dB to very loud sounds of 120 dB over a wide range of frequencies.

An audiogram plots a “threshold,” which is the softest intensity level the person can hear as a function of frequency and intensity. People with thresholds of 20 dB or below are considered to have normal hearing.

Hearing Loss
What is hearing loss? Hearing loss refers to a decrease in a person’s sensitivity to sound. Alternatively, hearing loss is an increase in a person’s threshold to sound.

Types of Hearing Loss
There are two different types of hearing loss—conductive and sensorineural.

Conductive hearing loss: is when the sound is blocked by something typically in the outer or middle ear, which prevents sound from getting to the inner ear. Conductive hearing losses are often medically treated with medication (such as for a middle ear infection) or removal of the blockage.

Sensorineural hearing loss: is when there is damage to inner ear’s sensory cells or parts of the hearing nerve. Damage to these sensory or neural structures results in a permanent hearing loss. There is no medical “cure” (such as medication) for sensorineural hearing loss.

Sensorineural hearing loss can sometimes be caused by overexposure to loud sounds, head injury, or infections. Sensorineural loss can be acquired gradually as you age. You can also be born with a hearing problem, called congenital (at birth) hearing loss, which can be caused by infection, illness, viruses, certain medications, lack of oxygen, or other birth complications, improper development, and genetics. Often, the exact cause of a hearing loss is difficult to identify.

Degree of Hearing Loss
Hearing losses will range in degree from mild to profound depending on the extent of sensory cell loss or damage.

Mild Hearing Loss: is designated by hearing sensitivity in the 25 dB–40 dB range. People with a mild hearing loss have difficulty hearing and understanding very soft sounds.

Moderate Hearing Loss: is designated by hearing sensitivity in the 40 dB–70 dB range. Those with a moderate loss have difficulty hearing soft sounds and understanding conversation, especially in noisy environments. Often with moderate loss, people don’t know what they are missing, like when they can’t hear someone calling their name.

Severe Hearing Loss: is designated by hearing sensitivity in the 70 dB–90 dB range. People with a severe hearing loss cannot hear soft sounds, whispers, birds singing, or conversational level speech.

Profound Hearing Loss: is designated by the 90 dB and greater range. Often, people with profound hearing loss are referred to as “deaf.” Those with profound hearing loss can typically only hear very loud environmental sounds.

Next: Treatments for Hearing Loss>>