Kenta Yamamoto


2025

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Analysis of Voice Activity Detection Errors in API-based Streaming ASR for Human-Robot Dialogue
Kenta Yamamoto | Ryu Takeda | Kazunori Komatani
Proceedings of the 15th International Workshop on Spoken Dialogue Systems Technology

In human-robot dialogue systems, streaming automatic speech recognition (ASR) services (e.g., Google ASR) are often utilized, with the microphone positioned close to the robot’s loudspeaker. Under these conditions, both the robot’s and the user’s utterances are captured, resulting in frequent failures to detect user speech. This study analyzes voice activity detection (VAD) errors by comparing results from such streaming ASR to those from standalone VAD models. Experiments conducted on three distinct dialogue datasets showed that streaming ASR tends to ignore user utterances immediately following system utterances. We discuss the underlying causes of these VAD errors and provide recommendations for improving VAD performance in human-robot dialogue.

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Developing Classifiers for Affirmative and Negative User Responses with Limited Target Domain Data for Dialogue System Development Tools
Yunosuke Kubo | Ryo Yanagimoto | Mikio Nakano | Kenta Yamamoto | Ryu Takeda | Kazunori Komatani
Proceedings of the 15th International Workshop on Spoken Dialogue Systems Technology

We aim to develop a library for classifying affirmative and negative user responses, intended for integration into a dialogue system development toolkit. Such a library is expected to highly perform even with minimal annotated target domain data, addressing the practical challenge of preparing large datasets for each target domain. This short paper compares several approaches under conditions where little or no annotated data is available in the target domain. One approach involves fine-tuning a pre-trained BERT model, while the other utilizes a GPT API for zero-shot or few-shot learning. Since these approaches differ in execution speed, development effort, and execution costs, in addition to performance, the results serve as a basis for discussing an appropriate configuration suited to specific requirements. Additionally, we have released the training data and the fine-tuned BERT model for Japanese affirmative/negative classification.

2024

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Character Expression and User Adaptation for Spoken Dialogue Systems
Kenta Yamamoto
Proceedings of the 20th Workshop of Young Researchers' Roundtable on Spoken Dialogue Systems

The author is interested in building dialogue systems with character and user adaptation. The goal is to create a dialogue system capable of establishing deeper relationships with users. To build a trustful relationship with users, it is important for the system to express its character. The author particularly aims to convey the system’s character through multimodal behavior. Users currently try to speak clearly to avoid speech recognition errors when interacting with SDSs. However, it is necessary to develop SDSs that allow users to converse naturally, as if they were speaking with a human. The author focused on user adaptation by considering user personality. In particular, the author proposes a system that adjusts its manner of speaking according to the user’s personality. Furthermore, the author is interested not only in adjusting the system’s speaking style to match the user but also in making the system’s listening style more conducive to natural conversation.

2022

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Simultaneous Job Interview System Using Multiple Semi-autonomous Agents
Haruki Kawai | Yusuke Muraki | Kenta Yamamoto | Divesh Lala | Koji Inoue | Tatsuya Kawahara
Proceedings of the 23rd Annual Meeting of the Special Interest Group on Discourse and Dialogue

In recent years, spoken dialogue systems have been applied to job interviews where an applicant talks to a system that asks pre-defined questions, called on-demand and self-paced job interviews. We propose a simultaneous job interview system, where one interviewer can conduct one-on-one interviews with multiple applicants simultaneously by cooperating with the multiple autonomous job interview dialogue systems. However, it is challenging for interviewers to monitor and understand all the parallel interviews done by the autonomous system at the same time. As a solution to this issue, we implemented two automatic dialogue understanding functions: (1) response evaluation of each applicant’s responses and (2) keyword extraction as a summary of the responses. It is expected that interviewers, as needed, can intervene in one dialogue and smoothly ask a proper question that elaborates the interview. We report a pilot experiment where an interviewer conducted simultaneous job interviews with three candidates.

2021

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A multi-party attentive listening robot which stimulates involvement from side participants
Koji Inoue | Hiromi Sakamoto | Kenta Yamamoto | Divesh Lala | Tatsuya Kawahara
Proceedings of the 22nd Annual Meeting of the Special Interest Group on Discourse and Dialogue

We demonstrate the moderating abilities of a multi-party attentive listening robot system when multiple people are speaking in turns. Our conventional one-on-one attentive listening system generates listener responses such as backchannels, repeats, elaborating questions, and assessments. In this paper, additional robot responses that stimulate a listening user (side participant) to become more involved in the dialogue are proposed. The additional responses elicit assessments and questions from the side participant, making the dialogue more empathetic and lively.

2020

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An Attentive Listening System with Android ERICA: Comparison of Autonomous and WOZ Interactions
Koji Inoue | Divesh Lala | Kenta Yamamoto | Shizuka Nakamura | Katsuya Takanashi | Tatsuya Kawahara
Proceedings of the 21th Annual Meeting of the Special Interest Group on Discourse and Dialogue

We describe an attentive listening system for the autonomous android robot ERICA. The proposed system generates several types of listener responses: backchannels, repeats, elaborating questions, assessments, generic sentimental responses, and generic responses. In this paper, we report a subjective experiment with 20 elderly people. First, we evaluated each system utterance excluding backchannels and generic responses, in an offline manner. It was found that most of the system utterances were linguistically appropriate, and they elicited positive reactions from the subjects. Furthermore, 58.2% of the responses were acknowledged as being appropriate listener responses. We also compared the proposed system with a WOZ system where a human operator was operating the robot. From the subjective evaluation, the proposed system achieved comparable scores in basic skills of attentive listening such as encouragement to talk, focused on the talk, and actively listening. It was also found that there is still a gap between the system and the WOZ for more sophisticated skills such as dialogue understanding, showing interest, and empathy towards the user.