Auditory Processing Disorders
APD is a physical hearing impairment, but one which does not show up as a hearing loss on routine screenings or an audiogram. Instead, it affects the hearing system beyond the ear, whose job it is to separate meaningful message from non-essential background sound and deliver that information to the intellectual centers of the brain (the CNS). These students do not hear the subtle differences between the sounds of words.
In classrooms where most instruction is given verbally, these students are at risk of not understandind assignments, goals, and objectives. An APD can interfere directly with speech and language, but can affect all areas of learning, especially reading and spelling.
From LDonline: Living and Working with a CAPD