Single Sided Deafness
Hearing News • August, 29 2018
“Ears may come in pairs, but that doesn’t mean hearing conditions necessarily come in twos as well.”
Rory Thompson, Hearing Care Consultant
That’s a good thing, because in many cases hearing loss in one ear can be improved through the other. Single-sided deafness (SSD) is a condition in which a person has lost hearing in one ear, while he or she may have anywhere from normal hearing to profound hearing loss in the other.
We were designed to have two ears for a reason; the brain uses both ears for elevated volume, to pinpoint the direction of a sound and for additional processing power.
Losing the function in one ear severely limits a person’s hearing on a variety of levels:
Sound localisation: Your brain knows which direction a sound is coming from by which ear receives the sound first. When a person can only hear from one ear, he or she may have difficulty figuring out where the sound originated.
Hearing in noise: Your brain is also in charge of selective listening, which is tougher without the aid of a second ear. In a noisy environment, a person with SSD can struggle to focus on a single person’s voice.
Cognitive load: This refers to the act of listening while performing other tasks, which can be complicated even for a person with normal hearing. The more noise there is, the longer it takes the brain to focus and the person to complete the task. If the person is also trying to listen to someone speak, he or she will miss a significant amount of what is being said.
Binaural loudness summation: The brain “hears” a sound more loudly when it’s perceived through both ears than if the same sound at the same decibel were only perceived through one ear. This is because the brain reads nerves located in both ears and uses this information to process sounds.
The Head Shadow Effect
Patients with SSD often experience a phenomenon called the head shadow effect, in which sounds that originate on the side of the deaf ear are lost to the listener completely. Low-frequency, long-wavelength sounds bend around a person’s head, and are often perceived well even though the deaf ear may be turned in the direction of the sound.
High-frequency, short-wavelength sounds, however, are not as elastic and do not bend around to the side of the good ear. Thus many high-frequency sounds are lost to a person with SSD. Consonant sounds in speech occur as high-frequency sounds, so a person with SSD can often miss a significant amount of surrounding conversation.
There are a number of potential causes of SSD, including:
Physical damage to the ear
Viral or bacterial infection
Circulatory system disorders
SSD is often permanent, but is sometimes treatable through the opposite ear. Our Hearing Care Consultants at Thompson Hearing Services will perform a hearing test on you, and ask you questions to try and identify the cause of your SSD. From there, he or she might recommend one of two hearing aids for you:
Contralateral Routing of Sound (CROS) Hearing Aid
A CROS hearing aid consists of a transmitter, which is placed in the deaf ear, and a receiver, which is placed in the functioning ear. As sounds hit the deaf ear, the transmitter will communicate them to the receiver in the other ear.
Bone-anchored hearing device
Bone-anchored hearing devices are a surgical alternative, in which a titanium screw is anchored in the skull bone behind the deaf ear. A vibrating sound processor is attached externally, which reads sounds and transmits them through the skull bone to the cochlea of the good ear.