More than 1 in 6 Americans experience hearing loss today. This represents approximately 48 million people affected by some degree of hearing loss, and while the number may seem high, solutions exist for many of them.
Hearing loss can be subtle: the television seems too quiet, or a phone conversation becomes difficult to follow. Other signs are more obvious, such as when you no longer hear loud noises like construction equipment or a gunshot.
Does this sound familiar? These are just a few of the symptoms of hearing loss. If you or a loved one are concerned about your hearing, consult your primary care physician to discuss these symptoms and get a possible diagnosis.
How Hearing Works
Sound travels as an energy wave through the outer ear, passes through the middle ear, and then the inner ear, where this energy creates vibrations transmitted by the auditory nerve to the brain, which then reconstructs the sound.
In many people affected by some degree of hearing loss, the path of sound in the ear canal is disrupted, or a lesion in the inner ear alters this process.
Since we hear in stereo, sound is perceived simultaneously by both ears: an obstruction or injury to only one ear can therefore degrade the overall quality of hearing. We hear in stereo because it allows us to determine the direction from which sound comes, our distance from the source, and because it improves the clarity of what we perceive. Damage to a single ear can disrupt each of these functions of stereophonic hearing.
There are many causes of hearing loss: heredity and congenital malformations, trauma, illness, or aging — all factors that we examine in more detail in this article.
What are the different degrees of hearing loss, how does it occur, and what can be done for those affected?
Before discussing the amplification process and how hearing loss develops, it is important to understand the degrees and types of hearing loss.
What is Hearing Loss
Hearing loss occurs when sound can no longer be deciphered.
Symptoms range from muffled sounds to speech that is difficult to understand.
There may be a sensation of blocked ear or pressure, balance can be affected in more severe cases, and pain is another possible symptom. A normal conversation can feel like the person you are talking to is whispering or mumbling, especially in a crowded and noisy place.
Other symptoms include permanent ringing in the ears, called tinnitus. Phone conversations become difficult to understand, and a feeling of pressure develops in the ear.
Causes range from minor obstructions or fluid trapped in the ear canal — for example, when earwax builds up and retains fluid — to much more serious damage, such as prolonged exposure to loud music. Aging, congenital malformations, genetic factors, and trauma are also common causes of hearing loss.
The Main Types of Hearing Loss
Hearing loss is divided into three categories:
Conductive hearing loss: conductive hearing loss is due to an obstruction in the outer or middle ear that prevents sound from reaching the inner ear and brain; it can be temporary.
Sensorineural hearing loss: sensorineural hearing loss occurs when a problem in the inner ear or auditory nerve prevents sound from reaching the brain. This type of damage is usually permanent, although hearing aids and other forms of amplification can partially remedy it.
Mixed hearing loss: mixed hearing loss combines an obstruction in the outer or middle ear with permanent damage to the inner ear or auditory nerve.
In the case of conductive hearing loss, there are sometimes non-surgical solutions, but more severe forms may require surgery or hearing aids.
In cases of sensorineural hearing loss, no operation can repair the tiny hair cells in the inner ear. However, cochlear implants can help limit less severe sensorineural losses.
In cases of mixed hearing loss, solutions depend on the conductive and sensorineural components. Once diagnosed, your doctor or audiologist will explain the corrective procedures and options available to you.
The 4 Degrees of Hearing Loss
There are four degrees of hearing loss: mild, moderate, severe, and profound. The impairment intensifies at each stage, from slight discomfort to almost total hearing loss at the profound stage.
Mild Hearing Loss
Mild hearing loss can be temporary, for example, during a cold or when fluid gets stuck in the ear. With the widespread use of in-ear headphones, this is now the most common degree of hearing loss.
In cases of mild hearing loss, sounds are slightly muffled, and some become a little more difficult to perceive than with intact hearing. At this stage, people who speak softly and young children fall into a frequency range that is more delicate to hear than with normal hearing.
Another difficulty at this stage is that understanding a conversation at a normal volume in a noisy environment, such as a busy restaurant, becomes a little more laborious. At the upper limit of mild hearing loss, some consonants become confused, especially softer ones like "s." This degree of hearing loss is like putting your fingers in your ears or wearing earplugs: you still hear, but the sound is fainter and a little harder to grasp.
Moderate Hearing Loss
Moderate hearing loss is just beyond the mild stage. At this stage, it becomes difficult to follow a normal conversation, and the television or radio set at a normal volume is hard to hear. Affected individuals often ask their interlocutors to repeat themselves and sometimes unconsciously start lip-reading to reconstruct garbled words.
In addition to some difficult-to-perceive consonants, vowels become indecipherable at the upper limit of moderate hearing loss. At this degree of impairment, sounds are well perceived, but distinguishing words in a conversation can be very difficult.
Severe Hearing Loss
At this stage, speech and everyday sounds can no longer be deciphered without a hearing aid. In other words, understanding speech becomes very difficult without amplification, and sounds in a noisy environment become nothing but a wall of noise.
At this degree of hearing loss, even a normal conversation is inaudible without amplification. And even with hearing aids, understanding words can remain complicated: amplification, especially with analog devices, increases the volume of sound without necessarily improving its clarity.
Profound Hearing Loss
Profound hearing loss ranges from near-deafness to total deafness. Loud noises and explosions are barely perceived, and speech and everyday sounds remain inaudible, even with amplification.
At this degree of hearing loss, even with hearing aids, the person perceives garbled speech or does not hear it at all. At this stage, it is best to turn to other modes of communication, such as sign language or writing.
How We Hear
As mentioned above, hearing relies on the journey of sound energy through the outer, middle, and inner ear, before being translated by the brain into perceived sound.
When hearing is normal, we perceive higher and fainter sounds than when an obstruction or other impairment disrupts this process.
The outer ear is the visible part of the ear: the earlobe and the structure of the ear, called the auricle, as well as the ear canal. The eardrum, also called the tympanic membrane, separates the outer ear from the middle ear.
The middle ear consists of three small bones, the ossicles, better known as the hammer, anvil, and stirrup, as well as the eardrum.
The inner ear houses the snail-shaped cochlea, the auditory nerve, and spiral cavities that contribute to balance.
When sound travels through the three stages of the auditory system, any damage or obstruction hinders its transmission and leads to hearing loss.
Furthermore, the auditory nerve connects the inner ear to the brain and transmits the energy that will be converted into sound.
How Sound Is Measured
Sound is measured in two ways: volume and frequency. To determine your hearing level, you need to undergo an audiogram, which measures the volume at which you perceive a sound, the range of frequencies you can hear, and looks for potential causes of hearing loss.
Sound volume is measured in units called decibels, or dB. The higher the dB number, the louder the sound; in some forms of hearing loss (profound), even the loudest sounds may remain inaudible.
Some sounds are at the low end of the scale, like breathing at 10 dB, while very loud sounds like a gunshot reach 140 dB. Beyond 140 dB, it approaches the threshold of pain, and without protection, exposure causes damage.
Frequency is measured in units called hertz, or Hz. Frequency, also called pitch, ranges from 250 Hz to 8000 Hz, a range that corresponds to human speech.
How Hearing Loss Is Measured
As we have seen, hearing loss is measured by the volume needed to perceive sounds and by how easy or difficult it is to hear different frequencies.
How a Hearing Test Is Conducted
A hearing test is performed by an audiologist, a hearing specialist. There are generally three main types of tests to determine the severity and nature of the impairment.
During the first test, the patient sits in a soundproof booth with headphones while the audiologist plays different sounds and pitches, and asks them to react in a specific way as soon as they perceive a sound.
For example, to test the left ear, the patient must raise their left hand as soon as they hear a sound on that side. Sounds of various levels and frequencies are emitted, with increasing intensity, until the patient reacts.
The next test has two parts and uses a tuning fork placed against the head, either behind the ear (Rinne test) or on the forehead (Weber test).
The Rinne Test and the Weber Test
The Rinne test determines whether it is a bone conduction loss or an air conduction loss.
When hearing is hindered by an obstruction in the outer or middle ear, this affects air conduction. When the patient hears the tuning fork placed on the mastoid bone (behind the ear), the impairment concerns the inner ear.
For the Weber test, the tuning fork is placed in the center of the forehead. With normal hearing, the sound is perceived stereophonically, meaning simultaneously by both ears.
The tuning fork is then moved laterally, from side to side, to determine the type of impairment. When the hearing loss is conductive, the sound is perceived in the ear on the side where the tuning fork is placed; when it is sensorineural, it is perceived in the opposite ear.
Understanding Hearing Loss, for You and Your Loved Ones
Whether it is you or a loved one who is experiencing hearing difficulties, consult your doctor and request a hearing test. Many forms of hearing loss can be corrected with hearing aids or cochlear implants.
Many impairments are preventable: simply wear appropriate hearing protection whenever you expect to be exposed to sudden or prolonged noise.
Understanding the four degrees of hearing loss, the types of impairment, and the available solutions is essential. But obtaining a professional diagnosis and a hearing test to determine the nature and extent of the impairment remains indispensable.
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