中文單音節語音之清晰度與聲場雙耳互函數關連性

Word Intelligibility in Relation to the Magnitudes of the Interaural Cross-Correlation Function of Mandarin Monosyllables

Previous studies have found that the speech intelligibility of Mandarin monosyllables is in direct correlation to the effective duration of the autocorrelation function (e) of the syllable itself at the same reverberation levels (Chen and Chan, 2006; Chen, 2012). In addition, it has been further found (Chen, 2004) that the evaluation of a sound field is the opposite between the speech transmission index (STI, proposed by Steeneken and Houtgast, 1973) and magnitude of the interaural cross-correlation coefficient (IACC) where the slope of the ceiling was changed in a hall in a constricted range of STI (0.5~0.7). Takaoka et al. (2007) once used noises and utterances in Japanese to examine the influence of a sound field's reverberation time and the IACC on speech articulation. They found that under an IACC condition where the SNR (signal-to-noise ratio) was between 0 dB ~10 dB and reverberation time varied between 0.5s~4.0s, no obvious changes were noticed in speech articulation, and that only when SNR was lower than-10dB, did the IACC affect speech articulation within a range of IACC limited to between 0.5~1.0. Accordingly, this study focuses on a broadened IACC range (0.34~0.87), and adopts paired comparison to identify the relationship between word intelligibility and the IACC with or without subsequent reverberation energy in detail. The results show that the word intelligibility of a monosyllable could be affected by reverberation time (p＜0.001), but not by IACC. The effect of the IACC was significant only in an environment with reverberation energy (p＜0.05). 在先前研究中我們發現中文單音節語音與聲場語音自函數（autocorrelation）之有效遲延時間有著良好的相關性（陳炯堯與詹旻憲，2006；陳炯堯，2012）。此外我們也發現Houtagst and Steeneken（1973）的語言傳遞指標（speech transmission index，STI）在具斜面天花的空間中僅有0.5～0.7的區間中，其評價與聲場之雙耳互函數（inter-aural cross-correlation coefficient，IACC）呈現相反的趨勢。Takaoka et al.（2007）曾以噪音環境中日文發音在迴響時間（reverberation time，RT）與雙耳互函數交替影響下討論對語音可聽程度的影響。發現在背景噪音下，訊噪比（signal to noise ratio, SNR）在0dB～10dB的範圍與迴響時間在0.5s～4.0s之間改變IACC條件下，對於可聽程度沒有影響。只有在SNR較低的時候（-10dB以下），IACC的改變會影響可聽程度。不過研究中IACC條件變化範圍僅在於0.5～1.0之間且非一般廳堂分布範圍。本研究則著眼於音樂廳自然的IACC變化範圍（0.34～0.87）；同時以具迴響與不具迴響能量的聲場條件交互檢討對單音節語音之可聽程度的影響。並在心理實驗中以配對比較（paired-comparison）法來進行單音節語音之可聽程度與IACC之關聯性研究。結果顯示整體單音節語音之可聽程度受到迴響時間的影響（p＜0.001）；而IACC對於單音節語音之可聽程度影響則須具有迴響條件（p＜0.05）。