Designers have long used spatial audio for both functional and aesthetic purposes to create impactful user experiences across a broad range of applications.When considering actual design practice, however, the spatial characteristics of sound are often determined in a later step of the design process.We argue that this introduces frictions that prevent practitioners from making the most of the medium.In this paper, we therefore explore how audio authoring tools can facilitate the design of spatial behavior alongside, and simultaneous to, other sound characteristics.To do so, we interviewed creative practitioners with spatial audio expertise to gain insight into how they collaborate and iterate to achieve their design goals.Following a Research-through-Design approach, we then applied the emerging themes to the design of an object-based spatial synthesizer.We reflect on lessons learned throughout its iterative development and discuss the challenges and opportunities of object-based spatial audio authoring tools.

The potential of spatial sound to immerse, guide, and affect humans is well-known, but has so far received little attention in the field of human-robot interaction. In this paper, we therefore explore how a robot emitting spatial sound affects a human’s impressions and behavior. Following a Research-through-Design (RtD) approach, we created two immersive robot sound designs which are emitted across the robot’s body and through speakers in the environment. In an evaluation study, participants interacted with the robot and shared their impressions through semi-structured interviews. Reactions showed that spatial robot sound had a notable effect on participant behavior and impressions, influencing, among others, how much attention they paid to the physical robot and how much animacy and agency they attributed to it. We report on our insights into how spatial sound may provide social robots with new ways to inform and engage the humans around them.

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, nonlexical (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 themargins of language, robotsmay 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].

Can we influence how a robot is perceived by designing the sound of its movement? Drawing from practices in film sound, we overlaid a video depicting a robot's movement routine with three types of artificial movement sound. In a between-subject study design, participants saw either one of the three designs or a quiet control condition and rated the robot's movement quality, safety, capability, and attractiveness. We found that, compared to our control, the sound designs both increased and decreased perceived movement quality. Coupling the same robotic movement with different sounds lead to the motions being rated as more or less precise, elegant, jerky, or uncontrolled, among others. We further found that the sound conditions decreased perceived safety, and did not affect perceived capability and attractiveness. More unrealistic sound conditions led to larger differences in ratings, while the subtle addition of harmonic material was not rated differently to the control condition in any of the measures. Based on these findings, we discuss the challenges and opportunities regarding the use of artificial movement sound as an implicit channel of communication that may eventually be able to selectively target specific characteristics, helping designers in creating more refined and nuanced human-robot interactions.

Rich and elaborate communication will play an essential part in the success of social robotics. The role of non-verbal sound as a communication channel has received relatively little attention in human-robot interaction research so far. Audio Cells is a prototyping environment for spatial sonic interaction design. It is part of my ongoing work on the sonification of artificial bodies. Through a combination of modular loudspeakers and sensors, it allows the exploration of a range of spatial interactive audio effects. By bringing methods from the fields of sound design and spatial audio into the context of human-robot interaction, my research aims to enrich and refine the ways robotic agents and responsive structures communicate with humans.