Dealing with Decreased Sound Tolerance – Hyperacusis and Recruitment
Do loud noises or specific sounds bother you? You may suffer from Decreased Sound Tolerance: hyperacusis and / or recruitment. The good news – help is available.
Most of us are irritated by loud noises. However, some individuals are particularly sensitive to normal levels of sound. Abnormal intolerance of sounds may be due to two different physiological phenomena:
• Hyperacusis – a brain phenomenon that decreases tolerance to normal levels of sounds
• Recruitment – intolerance to loud sounds caused by damage to the cochlea in the inner ear
Hyperacusis is a diminished tolerance to normal environmental sounds
It may vary from a mild to very severe discomfort to sounds which are not perceived as loud by other people. It can also be accompanied by ear pain and tinnitus.
In extreme cases of hyperacusis, individuals isolate themselves into confined, quiet environments, away from social interaction. Individuals with hyperacusis do not necessarily have a hearing loss, and it is also a fallacy that they may have “supernormal hearing”.
Hyperacusis and Central Processing of Sounds
Hyperacusis can be caused by trauma or insult to the brain causing an alteration in the central processing of sounds. This alteration may be chemically induced by toxic drugs or mechanically induced by head injuries. It can also be caused by psychological traumas. Contrary to many misconceptions, the organ of hearing is usually normal.
Meaning of Sounds and the Perception of Loudness
Our perception of loudness is not dictated solely by the strength or intensity of the sound entering our ears. It is also influenced by the meaning of the sounds and learned association in the central areas of the brain.
Over-sensitivity to a sound may begin with an irrational fear, and the central auditory processing mechanism becomes trained to listen and monitor minor sounds, which turns them into very loud, intrusive and unpleasant sounds.
Earplugs May Aggravate Sound Sensitivity
These unpleasant sensations caused by offending sounds often result in ill-advised individuals to over-protect their ears with earplugs to sleep for example. This only exacerbates the problem, as auditory deprivation aggravates sensitivity to sound. The best approach to managing hyperacusis is to gradually expose the affected ear to sound under professional guidance to achieve desensitisation.
Recruitment and Abnormal Perceived Loudness
Recruitment – is a sudden abnormal growth of perceived loudness in specific frequencies, which are affected by an accompanying hearing loss. The phenomenon is frequently found in individuals who have a hearing loss caused by a cochlear lesion such as in Meniere’s disease.
Sensorineural Hearing Loss
This type of hearing loss is described as “sensorineural hearing loss” although the term “cochlear hearing loss” is more precise.
Recruitment is caused by damage to the hair cells in the cochlea – the organ of hearing located in the inner part of the ear.
As sound levels entering the cochlea increase above a certain level, neighbouring inner hair cells are ‘recruited’, causing a sudden increase in perceived loudness and discomfort. The sensation is very similar to hyperacusis, but the mechanism is different.
Individuals with recruitment cannot hear softer sounds, but medium to loud sounds are perceived as extremely loud. Those with hyperacusis and no hearing loss have no problems to detect soft sounds.
Ear plugs are contra-indicated to individuals with hyperacusis and recruitment unless they are exposed to dangerous levels of sounds such as industrial noises.
Hearing Aids Can Provide Support
Hearing aids are the best solution for people who have a hearing loss and are sensitive to sound either due to recruitment or hyperacusis.
Digital hearing aids amplify soft sounds to audible levels and compress loud sounds down to comfortable levels. This means that loud sounds will no longer be perceived as too loud and softer sounds will be heard with no effort.
Cochlear Implants May Improve Hearing
As the hearing loss progresses, the effect of recruiting from different hair cells groups results in difficulties in processing and distinguishing between words. When hair cell loss becomes very severe a hearing aid will no longer be helpful, and a cochlear implant should be considered to improve hearing.
Best Treatment for Sound Sensitivity
In summary, the best treatment for sound sensitivity is sound exposure. Ear protectors such as earplugs and muffs should be avoided around normal levels of sounds as they create auditory deprivation and heighten sound sensitivity.
Seek Advice from an Audiologist
On the other hand, ear protection is highly recommended to prevent hearing damage whenever the ears are exposed to harmful loud noises. There is a fine line between over protecting your ears to the point of auditory deprivation and to use ear protection to avoid hearing damage. Your expert audiologist should be able to advise you on the best course of action for your case.