Empathetic Speech Synthesis and Testing for Healthcare Robots

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Empathetic Speech Synthesis and Testing for Healthcare Robots Jesin James1

· B. T. Balamurali2 · Catherine I. Watson1 · Bruce MacDonald1

Accepted: 10 August 2020 © Springer Nature B.V. 2020

Abstract One of the major factors that affect the acceptance of robots in Human-Robot Interaction applications is the type of voice with which they interact with humans. The robot’s voice can be used to express empathy, which is an affective response of the robot to the human user. In this study, the aim is to find out if social robots with empathetic voice are acceptable for users in healthcare applications. A pilot study using an empathetic voice spoken by a voice actor was conducted. Only prosody in speech is used to express empathy here, without any visual cues. Also, the emotions needed for an empathetic voice are identified. It was found that the emotions needed are not only the stronger primary emotions, but also the nuanced secondary emotions. These emotions are then synthesised using prosody modelling. A second study, replicating the pilot test is conducted using the synthesised voices to investigate if empathy is perceived from the synthetic voice as well. This paper reports the modelling and synthesises of an empathetic voice, and experimentally shows that people prefer empathetic voice for healthcare robots. The results can be further used to develop empathetic social robots, that can improve people’s acceptance of social robots. Keywords Social robots · Emotional speech synthesis · Artificial empathy · Prosody modelling · Healthcare

1 Introduction In Human-Robot Interaction (HRI), the focus is given to make robots learn to react to users socially and engagingly [1]. Such social robots are used for various applications such as education (e.g. [2]), passenger guidance (e.g. [3]) and healthcare (e.g. [1,4,5]). Healthcare robotics is the focus of this research study. The healthcare robot (Healthbots project [6]) [7,8] is an application of human-robot interaction under development at the Centre for Automation and Robotic Engi-

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Jesin James [email protected] B. T. Balamurali [email protected] Catherine I. Watson [email protected]

neering Science, the University of Auckland, New Zealand. This project aims to develop social robots that provide support and care to people living in nursing homes. The role of these Healthbots will be to assist the medical staff in agedcare facilities by being a companion to the aged people [9]. Currently, the technology is undergoing additional field trials in realistic environments and commercialisation [6]. This paper describes the journey towards developing an empathetic voice for Healthbots. The next two sections explains the motivation to develop an empathetic voice (Sect. 2) and details about empathy in social robot applications (Sect. 3). This is followed by Sect. 4 describing a pilot study conducted to understand if people prefer empathetic voice in Healthcare robots. Section 5. Further, emotional speech synthesis (Sect. 6) and another experiment (Sect. 7