  We present CALLS, a Japanese speech corpus that considers phone calls in a
customer center as a new domain of empathetic spoken dialogue. The existing
STUDIES corpus covers only empathetic dialogue between a teacher and student in
a school. To extend the application range of empathetic dialogue speech
synthesis (EDSS), we designed our corpus to include the same female speaker as
the STUDIES teacher, acting as an operator in simulated phone calls. We
describe a corpus construction methodology and analyze the recorded speech. We
also conduct EDSS experiments using the CALLS and STUDIES corpora to
investigate the effect of domain differences. The results show that mixing the
two corpora during training causes biased improvements in the quality of
synthetic speech due to the different degrees of expressiveness. Our project
page of the corpus is http://sython.org/Corpus/STUDIES-2.
