  In this paper, we propose a new framework for environmental sound synthesis
using onomatopoeic words and sound event labels. The conventional method of
environmental sound synthesis, in which only sound event labels are used,
cannot finely control the time-frequency structural features of synthesized
sounds, such as sound duration, timbre, and pitch. There are various ways to
express environmental sound other than sound event labels, such as the use of
onomatopoeic words. An onomatopoeic word, which is a character sequence for
phonetically imitating a sound, has been shown to be effective for describing
the phonetic feature of sounds. We believe that environmental sound synthesis
using onomatopoeic words will enable us to control the fine time-frequency
structural features of synthesized sounds, such as sound duration, timbre, and
pitch. In this paper, we thus propose environmental sound synthesis from
onomatopoeic words on the basis of a sequence-to-sequence framework. To convert
onomatopoeic words to environmental sound, we use a sequence-to-sequence
framework. We also propose a method of environmental sound synthesis using
onomatopoeic words and sound event labels to control the fine time-frequency
structure and frequency property of synthesized sounds. Our subjective
experiments show that the proposed method achieves the same level of sound
quality as the conventional method using WaveNet. Moreover, our methods are
better than the conventional method in terms of the expressiveness of
synthesized sounds to onomatopoeic words.
