Recent technological advances now make possible full integration of sound in instructional software. This paper explores the systematic use of sound to enhance learning and the operations and limiting factors of information-processing. It illustrates a model of the "instructional communication system" based on a combination of information-processing and communication theories. The model identifies and characterizes the way sound might be used to optimize learning from multimedia instruction. (Contains 45 references and 11 figures.) (Author/AEF)