# EmojiVoice: Towards long-term controllable expressivity in robot speech

arXiv: https://arxiv.org/abs/2506.15085 · HTML: https://mlsanity.com/paper/2506.15085/

## Key facts

- Cited by 2 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 18 Jun 2025.

## Built on by (most cited first, 2 of 2)

- [The Prosody of Emojis](https://mlsanity.com/paper/2508.00537/) (2025)
- [AphaVoice: Text-to-Speech Model for Aphasia Patient Simulation](https://mlsanity.com/paper/2610.14479/) (2026)

## Abstract (arXiv)

Humans vary their expressivity when speaking for extended periods to maintain engagement with their listener. Although social robots tend to be deployed with ``expressive'' joyful voices, they lack this long-term variation found in human speech. Foundation model text-to-speech systems are beginning to mimic the expressivity in human speech, but they are difficult to deploy offline on robots. We present EmojiVoice, a free, customizable text-to-speech (TTS) toolkit that allows social roboticists to build temporally variable, expressive speech on social robots. We introduce emoji-prompting to allow fine-grained control of expressivity on a phase level and use the lightweight Matcha-TTS backbone to generate speech in real-time. We explore three case studies: (1) a scripted conversation with a robot assistant, (2) a storytelling robot, and (3) an autonomous speech-to-speech interactive agent. We found that using varied emoji prompting improved the perception and expressivity of speech over a long period in a storytelling task, but expressive voice was not preferred in the assistant use case.