Auditory Processing Disorder (APD), also known as Central Auditory Processing Disorder (CAPD), is a hearing problem that affects about 3%–5% of school-aged children. It is a disorder of the auditory system at the level of the brain, in an area called the auditory cortex. People with APD can hear, but they may have trouble understanding certain sounds, especially speech, in noisy or challenging listening environments. They have difficulty hearing small sound differences in words, and their ears and brain dont fully coordinate, which interferes with the way the brain recognizes and interprets sounds. APD can happen after chronic ear infections, meningitis, lead poisoning, head injury, or nervous system diseases such as multiple sclerosis. It can also occur in both children and adults and may run in families. APD is not hearing loss or a learning disorder, and it is not the result of higher-order cognitive, language, or related disorders. There is no single cause of APD, and the treatment is specific to each individual. Testing for APD can only be done by an audiologist, who will do a series of advanced listening tests in which the person will listen to different sounds and respond when they hear them.