A unilateral hearing loss (UHL) affects one ear only. The child can hear normally in one ear and has some difficulty hearing with the other ear. There are different types, degrees and configurations of unilateral hearing loss and this will impact on how the hearing loss is managed.
The type of hearing loss depends on the site of the problem in the ear which may be anywhere from the outer ear through to the middle ear, inner ear and the auditory nerve which carries the sound impulses through to the auditory cortex in the brain.
Conductive hearing loss
Hearing loss associated with outer or middle ear problems is known as conductive hearing loss. Problems such as wax build up, middle ear infection (otitis media) or deformity of the outer or middle ear structures prevent sound being conducted to the inner ear. Sound is softened, making hearing difficult. Conductive hearing losses can often be treated with either medication or surgery.
Sensorineural hearing loss
Sensorineural hearing loss results from dysfunction in the inner ear and/or the auditory nerve. Most sensorineural hearing loss is due to abnormalities in the hair cells in the cochlea. Causes of hair cell abnormality include certain genes as well as external causes such as damage from loud music or infections. The quantity (loudness) and quality (clarity) of sound is affected in sensorineural hearing loss. Sensorineural hearing loss is permanent and cannot be treated with surgery.
Mixed hearing loss
A mixed hearing loss occurs when the cause of the hearing loss is both sensorineural and conductive. For example, a child with microtia and atresia with subsequent conductive hearing loss may also have a sensorineural hearing loss.
Table 2: Describing hearing loss
Hearing loss is categorised depending on what part of the auditory system is affected
The hearing loss is categorised according to the severity of the hearing loss
The overall picture of the hearing loss is described. For example:
Hearing loss is described as mild, moderate, severe and profound. The degree of hearing loss depends on how loud sounds need to be before the ear detects them.
Although your child is able to hear normally on one side, sounds coming from the direction of the deaf side are softer when heard by the hearing ear. This is due to the 'head shadow effect.' The sound must pass through or around the head to be heard by the functioning ear and results in a drop in the intensity or loudness of the sound. The child may hear the sound but it will be softer.
There is a difference between an 'audible' sound and an 'intelligible' sound. A child may be able to hear that someone is talking (the sound is audible) but not be able understand what exactly is being said (the sound is not intelligible). We have all had this experience in a noisy environment when we know someone is saying something to us but are unsure what they are actually saying. As adults, our experience may allow us to infer what is being said; we catch a few words and can therefore understand the gist of the conversation. Children cannot do this. They do not have the experience or mastery of the language to be able to pull the threads of the conversation together. Children need consistently intelligible speech to understand what is being said to them.
Parents often wonder what their child's hearing loss sounds like. There are simulators available for bilateral hearing loss but not unilateral hearing loss. By blocking one ear with an ear plug or cotton wool for a day, you can get some understanding of good and difficult listening environments for people with UHL.
The information below gives some indication of the degrees of hearing loss. This does not reflect the impact on the child with UHL when listening with both ears.
Table 3: Decibel comparison chart
This chart provides some indication of environmental sounds and their possible intensity or loudness.
|Source of sound||Decibel Level||Exposure effect|
|Normal conversation (at 1 metre)||50-65dB|
|Vacuum cleaner/hair dryer||80dB|
|City traffic (inside car)||85dB|
|Truck traffic||84-90dB||Prolonged exposure to any noise above 90dB can cause gradual hearing loss 8|
|Tractor||98dB||No more than 15 minutes exposure recommended without hearing protection8|
|Jackhammer/power saw||110dB||Regular exposure of more than one minute risks permanent hearing loss8|
|Jet take off||130dB|
The audiologist at Australian Hearing will record your child's hearing on a graph known as an audiogram and will discuss your child's audiogram with you. The audiogram will explain the type and degree of hearing loss and the frequencies affected by the hearing loss. This will assist the audiologist to discuss the management of your child's hearing loss with you.
09-Dec-2015 5:45 PM (AEST)