From introduction:
Sound is an important interaction modality and a large part of human interaction happens in the aural domain. While research in Human-Robot Interaction (HRI) has long explored spoken language for interacting with humans, sound as a broader—and, to a significant degree, non-lexical (i.e., without words)—medium has been given comparably less attention. Yet, the range of sounds that robots can produce is vast, encompassing, among others, mechanical noise, music, and utterances that mimic human and animal vocalizations with varying degrees of realism. The sound of a robot’s machinery can shape our perceptions and expectations [11, 17], music serves as a medium for robots to engage and communicate [18], and shared musical experiences can strengthen the bond between humans and robots [5]. Sonifications may enhance the legibility of movement and gestures [4, 7, 15] and beep sounds may be used to communicate emotions [2, 14]. Getting closer to the margins of language, robots may take inspiration from non-lexical fillers such as “uh” [13, 16] and backchannels such as “mhmm” [8, 12]. More generally, pitch, intensity, and other human prosodic variations may be drawn on in robot sound design [3, 10]. The information that can be extracted from sound in a robot’s environment is equally rich. Beyond the recognition of semantic content, robots use, for example, sound source localization to gain a better understanding of their environment [9], or analyze a human’s voice timbre and tone to distinguish speakers [6] and detect emotion [1].
The disciplines involved in these research pursuits are diverse, ranging from engineering, music, sound, and sonic interaction design to psychology, linguistics, and conversation analysis. However, there has so far been little knowledge exchange between the different disciplines despite them often tackling similar challenges around robot sound. This special issue aims to take a step towards unifying the Sound in HRI community, celebrating and showcasing the diversity of the different approaches while highlighting points of convergence.
While there are existing works that take a broader perspective on certain sound-related subfields, such as semantic-free utterances [19] or robotic musicianship, a central resource that provides a comprehensive overview of these diverse disciplines, and how they interact with each other, has yet to be created. This Special Issue is, to our knowledge, the first to address this by providing researchers with a broad picture of how the medium of sound can be utilized to enrich and refine interactions between robots and humans. The issue is meant for social robotics researchers and practitioners across academia and industry, both as an introduction for readers interested in entering the field, as well as a summary of findings and best practices for readers with prior experience. By showcasing the various ways in which sound informs, influences, and engages people, we aim to provide readers with new ways of using this modality to create richer, more nuanced HRIs.
Non-lexical vocalizations 