Jitter and shimmer appear as symptoms of disordered voices and they are defined as the cycle-to-cycle variation of the cycle length and cycle amplitude, respectively. The frequency modulation of the phonatory excitation, i.e. vocal jitter, causes amplitude modulation (shimmer) of the speech signal due to the action of the vocal tract transfer function. In this Letter, the authors investigate the extent to which the vocal tract filtering affects the accuracy of measurement of vocal cycle perturbations of the phonatory excitation. To achieve this goal, the direct digital synthesiser is used to generate a series of glottal excitation cycles with the desired amount of vocal perturbations that crosses the vocal tract model to produce a set of 231 stimuli of sustained vowels [a]. Praat is used to measure the amount of perturbations. Results show that the values of the input shimmer inserted in the glottal excitation are smaller than the values measured by Praat. An undesired amount of shimmer is generated in the speech signal when the glottal excitation signal perturbed with jitter crosses through the vocal tract.

中文翻译：

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声道滤波对声带周期扰动测量的影响

抖动和微光表现为声音紊乱的症状，它们分别被定义为周期长度和周期幅度的周期变化。由于声道传递函数的作用，发声激励的频率调制，即声音抖动，导致语音信号的幅度调制（微光）。在这封信中，作者调查了声道过滤对发声激发的声带周期扰动测量精度的影响程度。为实现这一目标，直接数字合成器用于生成一系列声门激发循环，其中包含所需数量的声音扰动，这些声音扰动穿过声道模型以产生一组 231 个持续元音刺激 [a]。Praat 用于测量扰动量。结果表明，插入声门激发的输入微光的值小于 Praat 测量的值。当受抖动扰动的声门激励信号穿过声道时，语音信号中会产生不希望有的微光。