分析音聲基頻變異方法之研究

Abstract

音聲的品質，主要決定於聲帶振動所產生的聲波。此聲波的規律性，也就是音聲基頻的穩定性，關係著音聲品質的好壞。因此分析音聲基頻的穩定性，即可對音聲品質做出適當的評估。以往對於分析音聲基頻變異的方式主要以抖動(Jitter)分析為主，但是抖動分析僅能提供音聲基頻變異量的程度並無法提供基頻訊號之變異頻率及功率分佈，使評估者無法明確的辨別音聲基頻變異的原因。因此本研究在此設計一新的分析音聲基頻變異法，藉由傅立葉及希爾伯特-黃轉換法提供基頻訊號的變異頻率範圍及功率分佈，以這些參數做為音聲品質的量化指標，以彌補抖動分析的不足。本研究找了40位音聲品質正常的受試者，共有20位男性及20位女性；6位音聲品質異常的病患，共2位男性，4位女性，被用來評估所提出的分析流程之效能。由實驗結果得知，對於聲帶振動體的材料及幾何特性不規則的病患而言，音聲基頻訊號確實會在10~25Hz的頻率範圍有異常的功率產生。 另外本實驗的結果亦顯示，單以音聲基頻的穩定性做為評估音聲品質的指標似乎是不足的。

Voice quality is determined by the regularity of the wave produced by the vocal folds, which also represents the regularity of the voice fundamental frequency. Analyzing voice fundamental frequency stability can therefore be a proper assessment of voice quality. Jitter analysis used to measure voice fundamental frequency stability has been for decades, but jitter analysis can only provide the voice fundamental frequency variation being normal or not. It cannot reveal the variation frequency and the variation power distribution, the measurement of jitter may have difficulties on evaluating the disease severity. Therefore, in this study a new method of analyzing voice fundamental frequency variation by Fourier and Hilbert - Huang Transform was designed. It provided the measurement of variation frequency and power distribution of the voice fundamental frequency signal. Forty subjects with normal voice quality, twenty males and twenty females; six patients with dysphonia, two males and four females, were studied. The results indicated that, hoarse voice signals had fundamental frequency with larger 10~25Hz variation power than normal voice. Additionally, evaluation voice quality only by voice fundamental frequency variation seems to be insufficient for describing the severity of dysphonia.