Final answer:
David likely has an auditory processing disorder, which affects how the brain interprets sounds, leading to heightened sensitivity to certain noises and less response to others.
Step-by-step explanation:
David's unusual responses to auditory stimuli are described as auditory processing disorder or a similar condition where the way the brain interprets sounds is affected. This can be part of a broader category of sensory processing disorders. His reaction to his mother's voice versus the sound of the chalkboard could indicate a heightened sensitivity to certain frequencies or types of sound, while possibly being less responsive to others.