  In this paper, we propose a framework for environmental sound synthesis from
onomatopoeic words. As one way of expressing an environmental sound, we can use
an onomatopoeic word, which is a character sequence for phonetically imitating
a sound. An onomatopoeic word is effective for describing diverse sound
features. Therefore, using onomatopoeic words for environmental sound synthesis
will enable us to generate diverse environmental sounds. To generate diverse
sounds, we propose a method based on a sequence-to-sequence framework for
synthesizing environmental sounds from onomatopoeic words. We also propose a
method of environmental sound synthesis using onomatopoeic words and sound
event labels. The use of sound event labels in addition to onomatopoeic words
enables us to capture each sound event's feature depending on the input sound
event label. Our subjective experiments show that our proposed methods achieve
higher diversity and naturalness than conventional methods using sound event
labels.
