Auditory processing disorder (APD) is a neurodevelopmental disorder affecting the way the brain processes sounds. Individuals with APD usually have normal structure and function of the ear, but cannot process the information they hear in the same way as others do, which leads to difficulties in recognizing and interpreting sounds, especially the sounds composing speech. It is thought that these difficulties arise from dysfunction in the central nervous system.
A subtype is known as King–Kopetzky syndrome or auditory disability with normal hearing (ADN), characterised by difficulty in hearing speech in the presence of background noise. This is essentially a failure or impairment of the cocktail party effect (selective hearing) found in most people.