College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China.
College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, Zhejiang, China; MOE Frontier Science Center for Brain Science and Brain-machine Integration, Zhejiang University, Hangzhou, Zhejiang, China.
Neurosci Biobehav Rev. 2023 Apr;147:105111. doi: 10.1016/j.neubiorev.2023.105111. Epub 2023 Feb 22.
The syllable is a perceptually salient unit in speech. Since both the syllable and its acoustic correlate, i.e., the speech envelope, have a preferred range of rhythmicity between 4 and 8 Hz, it is hypothesized that theta-band neural oscillations play a major role in extracting syllables based on the envelope. A literature survey, however, reveals inconsistent evidence about the relationship between speech envelope and syllables, and the current study revisits this question by analyzing large speech corpora. It is shown that the center frequency of speech envelope, characterized by the modulation spectrum, reliably correlates with the rate of syllables only when the analysis is pooled over minutes of speech recordings. In contrast, in the time domain, a component of the speech envelope is reliably phase-locked to syllable onsets. Based on a speaker-independent model, the timing of syllable onsets explains about 24% variance of the speech envelope. These results indicate that local features in the speech envelope, instead of the modulation spectrum, are a more reliable acoustic correlate of syllables.
音节是言语中可感知的显著单位。由于音节及其声学对应物，即语音包络，都具有在 4 到 8 Hz 之间的首选节奏范围，因此假设θ带神经振荡在基于包络提取音节方面起着主要作用。然而，文献调查显示，关于语音包络与音节之间关系的证据并不一致，本研究通过分析大型语音语料库重新探讨了这个问题。结果表明，仅当分析汇总了数分钟的语音记录时，语音包络的中心频率（由调制谱表征）才与音节率可靠相关。相比之下，在时域中，语音包络的一个分量与音节起始可靠地锁相。基于一个与说话者无关的模型，音节起始的时间解释了语音包络约 24%的方差。这些结果表明，语音包络中的局部特征而不是调制谱，是音节的更可靠的声学对应物。
