Conductive hearing loss is a type of hearing loss that occurs when sound is unable to pass through the outer and middle ear to reach the inner ear. Even though the primary organs responsible for processing sounds and sending signals to the brain are located in the inner ear, they will have no signal to transmit if sound does not reach them.
Every sound you hear goes through various stages during which sound waves are converted into electrical signals. When sound waves in the air enter the outer ear, they travel through the ear canal and reach the eardrum. When the eardrum receives these sound waves, it begins to vibrate. These vibrations are transmitted to tiny bones (the malleus, incus, and stapes) located in the middle ear. These small bones amplify the sound of the vibrations, then send them to an organ in the inner ear called the cochlea. The cochlea is filled with fluid. This fluid begins to ripple when the vibration reaches it. These ripples create a wave that travels along the basilar membrane. The basilar membrane is an elastic partition that separates the cochlea into an upper and lower section. It is the foundation upon which the cochlea rests. As the wave forms on the basilar membrane, the hair cells of the inner ear detect the vibration and begin to move up and down. As the hair cells move, their projections, called stereocilia, bump against the overlying structure and bend. When they bend, the stereocilia open, a chemical substance rushes into the cells, and an electrical signal is created. The auditory nerve carries this electrical signal to the brain. The brain then interprets these electrical signals into recognizable and understandable sounds.
Now that you know the detailed process of hearing, you have likely already understood the essential role played by the outer and middle ear. If the inner ear is functioning perfectly but no sound reaches it from the outer and middle ear, it cannot generate any electrical signal.
Conductive hearing loss often results from damage to the outer or middle ear. Both can be affected at the same time, although in many cases, one is more affected than the other.
In some cases, sound does successfully enter your ear, but its level decreases on the way to the inner ear. It then becomes difficult to hear quiet sounds, and loud sounds appear muffled.
The causes of conductive hearing loss
Before moving on to the symptoms of conductive hearing loss, let’s examine some of its causes. In this section, we will look at causes related to both the outer ear and the middle ear.
1. Earwax blockage
Earwax blockage is also called cerumen impaction. It forms when earwax accumulates in the ear canal and makes hearing difficult. Produced in normal amounts, earwax is beneficial for your ears. It is secreted by the body to prevent debris, liquids, and bacteria from reaching the inner ear. Accumulated earwax is normally expelled naturally. But when it is produced in excess, your ears may have trouble getting rid of it.
When the ear can no longer expel earwax, it accumulates and, most of the time, hardens. This blockage disrupts the transmission of sound to the ear. There are two main reasons for the formation of an earwax blockage. The first: earwax is pushed deeper into the ear canal by the use of objects such as cotton swabs. The second: the presence of excess hardened earwax. Conductive hearing loss due to earwax accumulation is generally temporary and disappears once the blockage is removed. In many cases, earwax can be safely removed at home using over-the-counter solutions, but some people will need to see a healthcare professional.
Once the excess earwax is removed from the ear canal, sound can once again travel effectively through the outer and middle ear to reach the inner ear.
2. Fluid in the ear
Fluid in the ear is also called otitis media with effusion (OME) or middle ear effusion (MEE). It involves an accumulation of fluid behind the eardrum in the middle ear, which can occur when the Eustachian tube (also called the auditory tube) is not functioning properly.
The fluid that accumulates in the middle ear is called serous fluid; it is generally clear or yellowish. This accumulation occurs when the Eustachian tube becomes inflamed or blocked and can no longer properly ventilate the middle ear or allow the fluid to drain.
Fluid in the ear can be caused by ear infections, colds, or allergies, all of which lead to inflammation that disrupts normal drainage through the Eustachian tube.
Children are more prone to middle ear effusion than adults due to anatomical differences in the Eustachian tube: in young children, it is shorter and more horizontal, which makes drainage more difficult. In adults, it is longer and more angled, which generally allows for better fluid drainage.
Otitis media with effusion often clears up on its own in a few weeks. If it persists or leads to hearing difficulties, a healthcare professional can examine you and suggest solutions to drain the fluid or relieve the pressure.
3. Eustachian tube dysfunction
The Eustachian tube is a small canal that connects the middle ear to the throat. It is responsible for draining fluid from the middle ear and balancing air pressure between the middle ear and the outside.
The Eustachian tube is usually closed to prevent any pressure buildup, but it opens briefly when you swallow, yawn, chew, or sneeze.
When this canal becomes blocked or no longer functions properly, it is called Eustachian tube dysfunction.
In this case, you may feel a sensation of ear fullness, muffled hearing, or discomfort.
Eustachian tube dysfunction can be caused by viral infections like the common cold, by sinusitis, or by allergies, which cause inflammation and excess mucus. It can also result from changes in altitude, for example while hiking, traveling by plane, or riding in an elevator.
In many cases, Eustachian tube dysfunction goes away on its own or with simple home remedies. If symptoms persist or are severe, a consultation with an ENT specialist may be necessary.
4. Perforated eardrum
A perforated eardrum, also called a ruptured eardrum or tympanic perforation, is a tear or hole in the thin membrane that separates the ear canal from the middle ear.
The eardrum plays an essential role in transmitting sound to the middle ear. A perforation can lead to conductive hearing loss, and both the size and location of the tear influence the severity of it.
Causes of a perforated eardrum include middle ear infections, barotrauma (pressure variations, such as in an airplane or while diving), exposure to loud noises, direct trauma to the ear, the introduction of foreign objects into the ear, and severe head trauma.
Fortunately, most perforated eardrums heal on their own within a few weeks. If healing does not happen naturally, the placement of a medical patch or surgical repair may be proposed. Once healing is achieved, hearing generally returns to normal.
5. Microtia
Microtia is a congenital malformation characterized by insufficient development or deformation of the outer ear. It generally occurs during the first trimester of pregnancy.
While the exact cause remains unknown, microtia has been associated with factors such as maternal diabetes, exposure to certain medications (like Accutane), alcohol consumption during pregnancy, and possible nutritional deficiencies, particularly in folic acid.
Microtia is classified according to its severity:
Grade I: The outer ear appears small but is largely present. The ear canal may be narrowed or absent.
Grade II: The upper part of the outer ear is malformed, while the lower third, including the lobe, is generally normal. The ear canal is narrowed or absent.
Grade III: The outer ear is only very slightly developed, with little cartilage or a small lobe. The ear canal is absent.
Grade IV (anotia): This is the most severe form, with total absence of the outer ear and ear canal.
Children with microtia often experience conductive hearing loss of varying degrees, partial or total, affecting one or both ears. In some cases, this hearing loss can also lead to speech and language delays if it is not addressed early.
Symptoms of conductive hearing loss
Here are some of the early symptoms of conductive hearing loss:
Difficulties hearing on the phone.
Poor understanding of speech, especially in noisy environments.
Turning up the volume of the television or radio beyond normal levels.
Difficulties following conversations.
The need to frequently have people repeat themselves.
Fatigue or stress related to listening, due to the concentration effort required to hear.
Early symptoms of conductive hearing loss
Here are some of the early symptoms of conductive hearing loss:
Difficulties hearing on the phone.
Difficulties hearing and understanding what others are saying, especially in crowded places.
Turning up the volume of the television or radio beyond the normal range.
Difficulties following conversations.
The constant need to have things repeated.
Fatigue or stress. These are related to the concentration effort required to hear what is being said.
General symptoms of conductive hearing loss
Common symptoms of conductive hearing loss — regardless of the cause — can include:
A muffled or dampened perception of sounds.
Sudden hearing loss in one or both ears.
Difficulties understanding speech, particularly in noisy places.
A sensation of fullness or pressure in the ear.
Ear pain or headaches, depending on the underlying cause.
Better hearing on one side than the other.
Difficulties hearing low-pitched or high-pitched quiet sounds.
Difficulties hearing consonants.
Asking others to speak more slowly, more clearly, or louder.
Withdrawing from conversations due to hearing difficulties.
In some cases (notably in the event of an infection), a yellowish or clear, foul-smelling discharge may occur.
Symptoms of conductive hearing loss in one ear
Unilateral conductive hearing loss (affecting only one ear) can be more difficult to detect because hearing in the other ear remains normal. Its symptoms are as follows:
Difficulties locating the source of sounds.
Difficulty distinguishing overlapping sounds.
Greater sensitivity to background noise.
Poor hearing on one side or in a given direction.
Difficulties hearing at a distance or in noisy environments.
Symptoms of conductive hearing loss in children and infants
Although this guide is dedicated to adults, it can be useful to know how to recognize the symptoms in children:
Reacting to visual signals but not to sound signals.
Not turning toward voices or loud noises between 4 and 6 months.
A speech delay or unclear articulation.
Speaking unusually loudly or turning the television volume up excessively.
Irregular reactions to sounds.
Asking for things to be repeated or giving unrelated answers to questions asked.
Symptoms according to the underlying cause
Earwax blockage:
Sensation of fullness or pressure in the ear.
Decreased hearing in the affected ear.
Tinnitus (whistling or buzzing in the ear).
Possible dizziness or balance problems.
Occasional ear discomfort or pain.
Ear discharge in the event of an infection.
Fluid in the ear:
Muffled hearing or a sensation of a blocked ear.
Ear pain, especially during changes in altitude.
Tinnitus or buzzing.
In rare cases, dizziness or balance problems.
In children, behavioral changes or school difficulties.
Eustachian tube dysfunction:
Pressure or sensation of ear fullness.
Muffled hearing.
Popping, clicking, or tickling sensations.
Discomfort or pain, especially during changes in altitude.
Tinnitus.
Balance problems in some cases.
Perforated eardrum:
Sudden hearing loss in the affected ear.
Discharge of clear, purulent, or bloody fluid.
Tinnitus.
Ear pain, which may disappear quickly.
Occasional dizziness or nausea if the inner ear is affected.
Conclusion
While some causes of conductive hearing loss are beyond your control, it is important to protect your ears whenever possible.
Avoid putting objects like cotton swabs or hairpins into your ears: this pushes earwax deeper and can cause a blockage. Earwax accumulation is a common — and avoidable — cause of conductive hearing loss.
Although loud noise is more often associated with sensorineural hearing loss, severe acoustic trauma can sometimes damage the eardrum and contribute to conductive hearing disorders. It is therefore prudent to avoid prolonged exposure to noisy environments.
If you notice hearing difficulties or if you experience the symptoms described above, do not hesitate to speak to a healthcare professional.
