Answer:
b. pitch increase
Explanation:
Sound is generally characterised by pitch, loudness and quality which in turn determines the auditory ability of an individual. The gradual process through which a student listening to a low-volume music hear the sound after becoming attentive is known as pitch increase.
Pitch, which is the response of the ear to frequency of the sound is directly related to the auditory perception of an individual. An increase in the pitch of a sound leads to a clearer sound being heard by an individual listening to a low-volume music after a given period of time.