Auditory Processing Disorder (APD), is also called Central Auditory Processing Disorder (CAPD), and Specific Learning Disability / Disorder with impairment in listening. It is quite common in Dyslexia.
While at Rutger's University in 1988, Dr. Paula Tallal, a cognitive neuroscientist, discovered that the APD brain requires 2 to 5 times longer to register a speech sound. The normal rate of speech is too fast for the APD brain to perceive and process all of the information heard. The result is a person who appears to have a long delay between what they hear and their response to it. When they do respond, the response may be inappropriate or may clearly indicate that they did not comprehend the information heard. They cannot accurately repeat auditory information. Parts are missing. It is not effective to give them spoken instructions because they require lots of repetition and redirection.
In 1996, Dr. Tallal developed Fast ForWord, a program that synthesizes speech sounds, elongating sounds so they can be registered by the APD brain. Over time, the program gradually shortens speech sounds until the APD brain can perceive and process sounds at a normal rate of speed. It is the only program scientifically designed and proven to correct the underlying processing glitch in the APD brain.
Dr. Paula Tallal's Video on Reading at the Speed of Speech (2010)
Why Auditory Processing Disorders are Often Overlooked | Auditory Processing, Cortical Oscillation Disruption in Dyslexia (2008, France)