My Dad suffers from Meniere's Disease. In addition to tinnitus and vertigo attacks, he is deaf in one ear. At least, sometimes he seems deaf in that ear. My family is often surprised to hear him say from another room that we are being too loud and it hurts his ears in response to us talking and laughing. Yet, when we call to him from the other room, he doesn't hear us. This phenomenon is known as recruitment.
Recruitment is part of a group of different types of sound sensitivity. This is when a person is unusually sensitive to certain sounds or all sounds, more so than the average population. The person may or may not have hearing loss depending on the type of sound sensitivity they have. The other types of sound sensitivity are Hyperacusis, where a person cannot tolerate normal environmental sound; hypersensitive hearing where specific frequencies at loud levels are a problem (this is common in children with autism); and Misophonia, where someone has an adverse reaction to a sound no matter how loud it is (the sound of people chewing or smacking their lips, for example).
So, what is Recruitment? Recruitment occurs when a person suddenly perceives a sound as too loud that he would not normally hear. In other words, the pitch of the sound is outside their hearing range (usually with someone with hearing loss), until it reaches a certain decibel. Then the hearing of that person suddenly "kicks on" and they not only hear the sound but it is perceived as way too loud, to the point of hurting their ears.
Why does Recruitment occur? In order to understand Recruitment, you must first understand what happens in certain types of hearing loss. The main organ responsible for hearing is called the cochlea. It is a tiny structure in the inner ear that is shaped like a snail. The cochlea is lined with thousands of tiny nerves called "hair cells." Each hair cell is responsible for hearing a certain sound. An analogy could be the keys on a piano but on a much more minute and detailed scale. The hair cells work together to arrange and send the sound to the brain, where it is heard and understood. When hair cells are damaged (whether by noise exposure or illness or trauma), you lose the ability to hear sounds in certain frequencies. With Recruitment, once the frequency hits a certain decibel, neighboring normal hair cells are "recruited" to hear the sound normally only heard by the damaged hair cells. The loudness of the sound shoots up suddenly and the sound is perceived as uncomfortable or painful.
Recruitment can be confusing to both the person experiencing it and to their friends and family. Fortunately, there is help. Tinnitus Retraining Therapy is a therapy that has been developed to help tinnitus and noise sensitivities such as Hyperacusis and Recruitment. Tinnitus Retraining Therapy is provided by specially trained doctors and audiologists who have been trained in this therapy. The therapy involves fitting the patient with special hearing aids that deliver broadband noise on a certain wavelength called pink noise. Pink noise is similar to white noise but on a different wavelength. The clinician will first diagnose your condition and explain the dynamics of it, test your ears for your loudness discomfort levels (the decibel level where you first experience discomfort), fit you with the hearing aids and then monitor your progress. Treatment typically lasts six months. Dr. Pawel Jastreboff is the audiologist who first developed this therapy and he has trained other clinicians to carry on his work.
Another option is ordering a broadband pink noise CD. The patient will listen to the pink noise through a compact CD player like a Walkman. It is important that the headphones are open air headphones and not in the ear. Pink noise can also be downloaded from the CD and into an iPod as long it remains in the original format. Regardless of whether you use the special hearing aids or the CD, it is important that you are under the guidance of a specially trained audiologist or doctor who works specifically with the Tinnitus Retraining Therapy (TRT).
Recruitment and other types of sound sensitivities can be frustrating for the people experiencing them and their loved ones. But with education, knowledgeable clinicians, and the right strategies and solutions, it can be managed and pose no barrier to a good quality of life.