Data_Sheet_1_An acoustic study of vocal expression in two genres of Yoruba oral poetry.zip

This pilot study proposes an acoustic study of the vocal expressions in Ìjálá and Ẹ̀sà, two genres of Yorùbá oral poetry. For this study, we conducted an experiment, involving the vocalization of an original poem in speech mode, Ìjálá and Ẹ̀sà. The vocalizations were recorded and analyzed acoustically. The results of the study show that cepstral peak prominence (CPP), Hammarberg index and Energy of voiced sound below 500 Hz distinguish comparisons of Ẹ̀sà, Ìjálá and speech but are not as reliable as F0 height and vibrato. By comparing the pitch trajectories of the speech tones and poetic tunes, we show that poetry determines tone-to-tune mapping but can accommodate language when it is feasible. The results of our investigation are not only in line with the previous impressionistic observations about vocal expression in Yorùbá oral poetry but contribute with new findings. Notably, our investigation supports vocal tremor as the historical origin of vibrato in Ìjálá. As a result of this, we strongly recommend the instruments of phonetic science for the study of vocal expression in African oral poetry.

本先导性研究针对约鲁巴语（Yorùbá）口头诗歌的两种体裁——Ìjálá与Ẹ̀sà中的发声表达开展声学研究。本次实验涵盖以言语模式、Ìjálá及Ẹ̀sà三种形式朗诵原创诗歌的发声环节，对录制的发声样本进行了声学分析。研究结果显示，倒谱峰突出度（cepstral peak prominence, CPP）、哈默伯格指数（Hammarberg index）以及500Hz以下浊音能量，可用于区分Ẹ̀sà、Ìjálá与日常言语的发声特征，但可靠性不及基频高度（F0 height）与颤音（vibrato）。通过对比言语声调与诗歌曲调的音高轨迹，本研究证实，诗歌主导声调-曲调的映射关系，但在可行条件下可适配语言本身的规则。本研究结果不仅与此前针对约鲁巴语口头诗歌发声表达的印象式观察结果一致，还补充了全新的研究发现。值得注意的是，本研究证实Ìjálá中的颤音（vibrato）其历史起源为发声震颤。基于上述结论，我们强烈建议采用语音科学的研究手段开展非洲口头诗歌的发声表达研究。