“In physics, sound is a vibration that travels through a medium—in our case, air—and produces what is called an acoustic wave. In humans, sound involves both the reception of acoustic waves and their perception. However, perception differs from person to person. In reality, our perception of sound is as unique as a fingerprint. In some cases, signals become confused, and diplacusis is a good example of this.” – Drew Sutton, MD, board-certified ENT specialist
There are several hearing disorders for which a diagnosis can be made. Sensorineural hearing loss, conductive hearing loss, tinnitus, and auditory processing disorders are the main categories of hearing disorders.
While these conditions are relatively common, this doesn't mean they never manifest in unique ways. One specific form of hearing loss is diplacusis. It is a disorder better known as "double hearing," which causes a person to perceive multiple sounds from a single stimulus.
Here's an overview of diplacusis, its connection to hearing loss, and what you can do to address it.
What is diplacusis?
Diplacusis is a hearing disorder characterized by distorted hearing. Specifically, a single sound is perceived as two distinct sounds instead of one. Diplacusis can be seen as the auditory equivalent of double vision.
The brain is usually very adept at merging multiple sensory inputs and making you perceive them as one, but in some cases, this doesn't happen. Many cases of diplacusis are accompanied by underlying hearing loss, but their manifestation still varies from person to person.
Diplacusis can affect one ear or both. When two sounds are heard in the same ear, it is called monaural diplacusis. Conversely, binaural diplacusis refers to cases where a sound is perceived differently from one ear to the other. Binaural diplacusis is the most common form of double hearing.
Here's a more detailed look at the different types of diplacusis and their supposed causes.
Dysharmonic diplacusis
Dysharmonic diplacusis is a subtype of diplacusis primarily based on double hearing related to a perceived pitch difference. It is one of the most common forms of diplacusis and can have several origins: an ear infection, exposure to loud noises, or a head injury.
Dysharmonic diplacusis is a common consequence of unilateral otitis. While most people go about their day simply noticing that one ear is slightly muffled or not quite right, professionals such as musicians and anyone who needs keen auditory acuity can find it much more difficult to perform their tasks to the best of their abilities.
Echoic diplacusis
Echoic diplacusis is caused by a time delay in sound perception. Essentially, when sound reaches the ears, one hears and interprets it faster than the other. The brain then becomes unable to interpret these sounds as one, resulting in an echo effect.
Echoic diplacusis can result from several ear problems, but it is most often related to the outer and middle ear. Conduction is the process by which sound energy is transferred and delivered to the neurosensory organ, the cochlea.
When sounds have a time delay but the same pitch, it indicates that something is slowing down the conduction process rather than an actual slowdown in sound perception. Earwax buildup, an ear infection, or any other obstruction can reduce the efficiency of sound propagation and cause an echo effect.
Mixed diplacusis
Mixed diplacusis occurs when both forms of auditory discrepancy manifest at the same time. This can create the impression of an echo accompanied by a slight pitch difference. Mixed diplacusis is rare and remains poorly understood. Many diagnose it as echoic or dysharmonic diplacusis, but this is of little importance, as the causes and treatments are very similar.
Is diplacusis curable?
Diplacusis takes many different forms and can have multiple causes. It is best considered a symptom: to get rid of it, the underlying health problem must be treated. In the case of diplacusis, this means properly managing the asymmetric hearing loss that causes it.
There are two main forms of hearing loss: conductive hearing loss and sensorineural hearing loss. Both can impair auditory acuity, but they differ in their physiological mechanism and management. Here's a more detailed look at these two forms of hearing loss and possible solutions.
Sensorineural
Sensorineural hearing loss affects the ears' ability to convert physical sound into nerve impulses. It is usually caused by a dysfunction of the cochlea or the auditory nerve.
The most common form of sensorineural hearing loss involves damage to the inner hair cells of the cochlea, which are responsible for detecting sounds and translating them into pitch and intensity. When these cells are damaged, the body's ability to perceive the affected tone decreases.
Sensorineural hearing loss is generally long-lasting, and treatments primarily aim to restore a quality of life that allows for better hearing of the world around you.
One of the most common medical interventions for sensorineural hearing loss is hearing aids. Hearing aids work by increasing the intensity of incoming sound waves and transmitting this amplified sound to the ear.
Conductive
Conductive hearing loss concerns the outer and middle ear. Many forms of conductive hearing loss can be treated and actually reversed: ear infections, earwax buildup, and canal obstructions. Obstructions and earwax can simply be removed, and normal hearing is usually restored.
Potentially long-lasting forms of conductive hearing loss include a ruptured eardrum or a congenital malformation of the middle and outer ear. A ruptured eardrum carries a risk of more permanent hearing loss. For its part, a malformation can reduce the ear's ability to properly conduct sounds to the cochlea, thereby diminishing sound perception.
More severe forms of conductive hearing loss often respond well to surgery, but hearing aids can also be used to amplify sound stimuli to a level capable of properly activating the cochlea.
Does diplacusis affect everyone in the same way?
An interesting observation is that diplacusis seems more noticeable in some people than in others. Those who regularly work with sound precision appear more sensitive to slight differences in sound perception and are more likely to notice when something is off.
A recent study also showed that among professional musicians, those specializing in classical music had a higher prevalence of diplacusis than others. The attention to accuracy and precision in classical music could explain why these musicians are more inclined to notice divergent auditory cues and seek help.
Treatments and prevention
While many factors can contribute to the onset of diplacusis, there are also many treatments and preventive measures that can relieve the discomfort associated with double hearing, or even prevent its onset.
Here's an overview of some treatments and prevention methods that can limit diplacusis or help you manage it better.
Preventing diplacusis
Preventing diplacusis primarily involves protecting your hearing. Your sense of hearing is robust, but exposure to certain medications, loud noises, or other environmental factors can contribute to hearing loss, which leads to diplacusis.
As mentioned above, musicians are at an increased risk of developing diplacusis and other hearing disorders such as tinnitus. As they rely heavily on sound for their careers, diplacusis can severely impair their activity. To prevent hearing loss, musicians can use musician's earplugs: these specialized protections uniformly reduce the intensity of all frequencies, allowing them to continue playing accurately.
Treating diplacusis
Both types of hearing loss can cause diplacusis. Therefore, it is important to seek help from a hearing care professional to identify the underlying cause of your diplacusis and guide you to the appropriate treatment. After a hearing test, the hearing care professional can determine if a hearing aid would benefit you.
In the case of conductive hearing loss, the hearing care professional may be able to resolve it if it is due to an obstruction or an ear infection. In cases of sensorineural hearing loss or severe conductive hearing loss, they can work with you to find the best solution for your needs.
Conclusion
In summary, diplacusis is a condition characterized by double sound perception. This can take the form of an echo or the same sound being perceived as two distinct pitches. Regardless of the type of diplacusis, it is essential to treat the underlying problem that distorts auditory perception. Addressing the hearing loss causing the disorder allows affected individuals to regain much more normal hearing.
Sources:
Types of Hearing Disorders | John Hopkins All Children’s
Ruptured Eardrum (Acutely Perforated Tympanic Membrane) | Cleveland Clinic
Hearing Loss, Tinnitus, Hyperacusis, and Diplacusis in Professional Musicians: A Systematic Review | NCBI
