The Sounds of Sorting Algorithms: Sonification as a Pedagogical Tool

Much work already exists on algorithm visualization-the graphical representation of an algorithm's behavior-and its benefits for student learning. Visualization, however, offers limited benefit for students with visual impairments. This paper explores algorithm sonification-the representation of an algorithm's behavior using sound. To simplify the creation of sonifications for modern algorithms, this paper presents a new Thread Safe Audio Library (TSAL). To illustrate how to create sonifications, the authors have added TSAL calls to four common sorting algorithm implementations, so that as the program accesses a value being sorted, the program plays a tone whose pitch is scaled to that value's magnitude. In the resulting sonifications, one can (in real time) hear the behavioral differences of the different sorting algorithms as they run, and directly experience how fast (or slow) the algorithms sort the same sequence, compared to one another. This paper presents experimental evidence that the sonifications improve students' long-term recall of the four sorting algorithms' relative speeds. The paper also discusses other potential uses of sonification.