Auditory Processing has been defined by APD pioneer, Dr. Jack Katz, as "What we do with what we hear." Our ears, when in healthy, undamaged condition, are like precision microphones. But in order for them to work as intended, they depend on the incredible processing of the central auditory nervous system (CANS) to receive their signals and convert them into meaningful, intelligible, and faithful reproductions of the sounds entering the ears. In effect, we ultimately "hear" with our brain, not our ears.Damage to the processor (the brain) will result in distorted, reduced-fidelity reproduction of inputs, no matter how intact they were leaving the transducer (the ear).
People whose conventional hearing evaluation indicates normal peripheral hearing at the ear-level have good "microphones." If they fail to experience quality sound perception–poor word recognition, difficulty extracting speech from degraded conditions (noise, poor acoustics, diminished-quality speech inputs), then the likely culprit is at the CANS level–the brain-stem or higher brain areas responsible for processing receptive auditory–specifically language–information. This is when a thorough central auditory processing (CAP) evaluation is recommended.
In the case of children, especially in their formative speech and language acquisition years, an auditory processing disorder (APD) can have disastrous effects on the appropriate development of auditory language, which can result in speech articulation problems, vocabulary and grammar problems, handwriting issues, and other problems. It logically follows that, since we reproduce what we "hear," disordered perceptions resulting from an APD will cause output errors in expressive language.
In some adults, APD may have been a factor most of their lives, just undiagnosed–especially in those who experienced significant difficulties in their educational history. Acquired APD can also result from head injuries, or acquired peripheral hearing loss (with resultant lack of auditory stimulation to the CANS areas), neurological disease, and from the normal processes of aging. Adults with pre-existing APD will frequently experience out-of-proportion hearing difficulty when their peripheral hearing becomes even marginally degraded due to aging or noise exposure. Research also indicates a significant increase in acquired APD among some menopausal women.
The symptoms of APD are very similar to the symptoms of a peripheral hearing loss (a hearing loss caused by a problem in the ear itself.) Although the sounds are loud enough, the person has difficulty understanding the message, therefore acting like someone with a hearing problem.Following is a list of symptoms teachers and parents have often observed in children with APD.
Adapted from Educational Audiology Association: Great Educational Handouts, Vol. 1, 1998. Developed by Gail G.Rosenberg, M.S., CCC-A, School Board of Sarasota County, FL. Reprinted with permission from the Educational Audiology Association.
The symptoms of APD in adults are very similar to the above listed for children. What is different for adults is that, since most have undiagnosed APD problems, they have, over time, developed coping mechanisms which may have compensated for some effects, or simply hidden–at least in part– the effects in others. A common hallmark associated with APD is difficulty listening in the presence of background noise or poor acoustical environments; however, the deficit may also be seen in one or more behaviors noted in the American Speech-Language-Hearing Association (ASHA) consensus statement on auditory processing disorders (ASHA, 1996): auditory discrimination, sound localization, difficulty understanding speech in competing noise and/or speech signals of degraded quality. Also recognizing auditory patterns and processing the temporal (time-based) elements of auditory signals can be impaired.
In addition to these deficits, commonly reported symptoms in adults with APD include: