Previous studies of multimedia presentations have determined the effects of the combination of text and pictures on vocabulary learning, but not those of the sound of new words. This study was intended to confirm those previous findings from the integration of mobile technologies and the approach of cognitive load. It adopted a within-subjects design and recruited 32 eighth graders in central Taiwan to participate in a vocabulary learning program on mobile phones. During the program the participants needed to learn four sets of target words in four different weeks. Each set was presented in one of the four modes: text mode, text-picture mode, text-sound mode, and text-picture-sound mode. Immediately after learning each set, all participants took a vocabulary test and completed a cognitive load questionnaire; and, two weeks later, they took the vocabulary test again. Their perceptions of the vocabulary learning program were also collected in a post-program questionnaire. The findings were that audio input helped our participants recall new words' meanings after two weeks; and, it reduced their cognitive load of learning new words. Our participants also provided positive feedback on the mobile-assisted vocabulary learning program featuring multimedia presentations.