Complex sentence: By sucking on a pacifier that would play the sound more related to the infants sucking, (high-amplitude sucking) the infant eventually became bored with or habituated to that particular sound and stopped sucking on the pacifier.
Split into simpler sentences: By sucking on a pacifier, this would play the sound more related to the infants sucking, (high-amplitude sucking). The infant eventually became bored with or habituated to that particular sound and stopped sucking on the pacifier.