Allow me to share some of Dr. Stephen Nagler's wisdom:
There are many misconceptions about hyperacusis and recruitment. Hearing professionals often oversimplify the concept of recruitment by stating that when hyperacusis occurs in a person with hearing loss, it is "recruitment." Moreover, you and I have both heard folks with severe hyperacusis claim that "my hyperacusis is so bad that I must have recruitment, too." In order to answer your question, then, I feel it is very important that these terms are defined properly. (Or at the very least, that you understand how "I" am defining them.)
1) Hyperacusis is a decreased threshold to discomfort from sound. It can range from a person who is mildly uncomfortable in a restaurant setting wherein all the rest of the people at the table have no discomfort at all ... to a person who has profound discomfort from many of the sounds encountered in daily life. TRT and other desensitization techniques can be highly effective in treating hyperacusis.
2) Recruitment is something completely different. Recruitment is the rapid growth of perceived loudness for those sounds located in the pitch region of a hearing loss. (This is Jack Vernon's definition.) So let me give you an example. My father had a significant hearing loss for several years before his death at the age of 89. I could say, "Dad." He heard nothing, and he of course did not respond. So I'd say it a bit louder. Still nothing. A bit louder than that. Still nothing. And then ... just a very tiny bit louder. The response: "Stop yelling so loud, Steve, I hear you just fine. Tone it down a bit, will you!" And THAT'S recruitment - a *rapid* growth of perceived loudness in a pitch region containing hearing impairment. (And it is very difficult to convey to a person with significant hearing loss that the time he hears my voice at a level uncomfortable to his ears ... was actually the *fourth* time I tried to get his attention.) This phenomenon occurs because at some decibel level, the normal hair cells adjacent to the damaged hair cells (corresponding to the frequency of a hearing loss) are "recruited." At the decibel level at which these normal hair cells "kick in," perceived loudness shoots up rapidly, causing discomfort. My professional opinion is that TRT and various desensitization protocols do not help in these cases... what is required is hearing aids (with compression, if the recruitment is severe). BUT - just because a person has some hearing loss and also has sound sensitivity ... it does not mean that the sound sensitivity is due to recruitment. Hyperacusis can occur in people with hearing loss!
For a further explanation of recruitment please visit this link: