Aim The aim of this study was to determine how deterioration of voice quality, such as breathiness, may impact on the intelligibility of speech. Method Acoustic analysis was conducted on sustained vowel phonation (/i/ and /a/) and sentences produced by voice disordered speakers. Measures included: frequency and amplitude of the first two formants (F1, F2), singing power ratio (SPR), the amplitude difference between the first two harmonics (H1-H2), voice onset time (VOT), and energy ratio between consonant and vowel (CV energy ratio). A series of two-way (glottal closure by vowel) mixed design between and within-subjects Analysis of Variances conducted on these acoustic measures showed a significant glottal closure (complete and incomplete) or glottal closure by vowel interaction effect on the F2 frequency, H1-H2 amplitude difference, and singing power ratio. Based on findings in literature that reported a dominant first harmonic as a useful predictor of breathiness, the measure of H1-H2 amplitude difference was selected as a factor for investigation of the impact of voice quality on the perception of vowel intelligibility and clarity. Fixed-length vowel segments at five levels of H1-H2 amplitude difference were presented to 10 male and 10 female inexperienced listeners between the ages of 19 and 34 years. Results It was expected that the tokens with a dominant first harmonic, indicative of a more breathy voice, would be associated with a lower rate of correct vowel identification and of being perceived as “clearer”. Although no linear relationship between breathiness and intelligibility was revealed, results indicated the presence of thresholds of intelligibility for particular vowels whereby once a level of breathiness was reached intelligibility would decline. Conclusion The finding of a change of the perceptual ratings as a function of the H1-H2 amplitude difference, identified in previous studies as a measure of breathiness, revealed thresholds of intelligibility for particular vowels below which breathiness would be tolerated with little impact on intelligibility but beyond which intelligibility ratings suffered markedly.

The change a speaker makes in response to background noise is known as the Lombard Effect (LE). This study investigated the acoustic changes that are undergone in the presence of broadband noise and two-talker babble. Of particular interest were vocal fundamental frequency (F0) and formant frequency vowel space measures across sex. Forty participants (20 male, 20 female) were recruited and asked to read phrases in quiet and in the presence of two-talker babble and broadband noise. These masker conditions were presented at 50 and 70 dB HL. The phrases were recorded and acoustically analysed. The results showed a significant sex difference for both F0 and vowel space. A masking condition effect was not displayed for either F0 or vowel space. A significant effect was however shown for F0 according to intensity level, suggesting a LE. While the sex difference in F0 values can be explained on the basis of differences in vocal anatomy, the sex difference in vowel space was indicative of a sociophonetic influence on speech production.

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本論文為以共振峰頻率資料來研究台灣華語母音音質之聲學研究。 本研究的受試者為六名生長在台灣台北市的男性華語母語使用者。本研究使用的測試字為70個包含所有韻母型態的單音節字。語音資料是利用KAY CSL 4100 (KAY Electronics)來錄製及分析。本研究所採用的資料為獨立發音且無聲母的測試字。 根據共振峰頻率資料本研究得到以下有關台灣華語母音音質的發現。首先研究的部分為音標所隱含的語音對比。在齒槽（alveolar）及後齒槽（post-alveolar）組的舌尖母音（apical vowels）間並沒有發現音質上的顯著差別，但統計及其它證據支持低母音裡的前後對比及中母音裡的半開（open-mid）及半閉（closed-mid）對比的存在。 其次，研究的結果也包括語音環境中的音段對於母音音質的影響。結果發現韻母中的元素，包含母音前介音、母音後介音、及韻尾鼻音，都對母音有不同的語音制約（conditioning）。另外，本研究發現順同化（progressive assimilation）比逆同化（regressive assimilation）對於低母音音質有較大的影響。 第三，本研究藉由與之前聲學研究的結果作比較來討論台灣母音音質的改變。結果發現硬顎及後硬顎組的舌尖母音間的音質差異隨著時間縮小終至於消失。此外，研究發現半閉母音及半開母音在母音高度及母音前後相對位置出現反轉。共振峰頻率的比較顯示這種反轉的原因為半閉母音[e]在音質上的改變。然而，我們需要進一步的研究才能對這些音質的改變有合理的解釋。 最後，本研究以共振峰頻率的形式描述及紀錄了當代台灣華語表層母音的音質。希望這些資料能對台灣華語母音的研究有所貢獻。 / This thesis is an acoustic study that investigates the vowel quality of Taiwan Mandarin vowels with formant frequency data. The subjects of this study included six male native Mandarin speakers born and raised in Taipei city, Taiwan. Testing items used in this study were 70 syllables that involve all combinations of segment in the syllable final. The speech data were recorded and analyzed with KAY CSL 4100 (KAY Electronics). The data discussed in this study were testing items produced in citation form without initial consonant. The vowel qualities of Taiwan Mandarin surface vowel were measured and analyzed. Several results concerning the vowel quality of Taiwan Mandarin surface vowel phones were reported based on the formant frequency data. Firstly, the distinction between vowel phones implied by their transcription was examined. The difference in vowel quality was not observed in the alveolar and post-alveolar groups of apical vowels, while the front-back distinction in low vowels and the open-mid and closed-mid distinction in mid vowels were found with statistic and other evidence. Secondly, the conditioning of segments in the neighboring environments on the vowel quality was investigated. It is found that elements in the syllable final, including pre-nuclear, post-nuclear glide and coda nasals, generally have different types of conditioning on the vowel. In addition, the progressive assimilation was found have greater influence on the vowel quality of low vowel phones than the regressive assimilation. Thirdly, the change in vowel quality was discussed through the comparison with results in previous acoustic studies. The difference in vowel backness between the alveolar and post-alveolar groups of apical vowels were found to be decreasing and eventually disappeared. Besides, the relative vowel height and backness of closed-mid and open-mid vowel were found to be in reverse compared with that in the literature. Comparison in formant frequencies showed that this reverse lay in the change of vowel quality in the close-mid [e]. However, further investigations were needed to offer reasonable explanations for the change. Finally, the vowel qualities of present Taiwan Mandarin surface vowel phones were described and recorded as the formant frequency data presented in this study. Hopefully, the data could contribute to the study of vowels in Taiwan Mandarin.

本論文為以共振峰頻率資料來研究海陸腔客語母音音質之聲學研究。 語言學的文獻中，以共振峰頻率資料來研究世界上各種語言的母音的音質已經有相當豐富的文獻，在過去五十年來，前人在客語的語音及音韻系統上已經有豐富的研究成果。但以聲學資料來對海陸客語做描述的文獻相當缺乏。 本研究的受試者為居住在新竹縣新埔鎮，六位以海陸腔客家話為母語的人士，其中有三名男性及三名女性。本研究使用了32個測試字，包含了單元音、雙合元音及三合元音。語音資料是利用KAY CSL 4100 (KAY Electronics)來做分析。本研究測試字包含的音節結構有:CV, CVV, CVVC, CVC, 以及CVVV。測試字在實驗的過程中，被受試者單獨發音，或是放在句子中間。在實驗資料完成分析後，我們以Origin 6.0軟體繪出海陸腔客語母音的聲學空間圖。 根據供振峰研究資料，本研究得到以下有關海陸腔客語母音音質的表現。首先關於單元音，海陸腔客語共有六個單元音: [i], [e], [ɨ], [a], [o], 以及 [u]。其次，海陸腔客語共有十一個雙元音: [ie], [ia], [io], [iu], [eu], [ai], [au], [oi], [ui], [ue], 以及 [ua]。我們比較單元音及雙元音的聲學空間圖(vowel space)後，發現相同的母音在雙母音的環境下，由於受到鄰近母音發音位置的影響，在聲學空間上，比起在單母音的時候，變的更高低，或更前或後。第三，三母音[iai], [iau]和[uai]在聲譜圖上的表現，第一個母音[i]和[u]都比其後的兩個母音，長度來的相對的短一些，表現很像是滑音[j]和[w]。 最後，本研究以共振峰聲學頻率的形式描述及記錄了當代海陸腔客語母音的音質，前人的研究中，以楊時逢(1952)最能說明本研究所提供的聲學資料。希望這些資料能對海陸腔客語母音的研究有所貢獻。 / This thesis is an acoustic study that investigates the vowel quality of Hai-lu Hakka vowels with formant frequency data. The acoustic method has been widely applied to the study of vowel quality of languages worldwide. In the past 50 years, Hakka researchers have yielded rich results in phonological system and phonetic description of Hakka, but there are relatively fewer research focus on the acoustic properties and characteristics of vowel phones in Hai-lu Hakka. The subjects of this study included three male and three female native Hai-lu Hakka speakers. Testing items used in this study were 32 syllables that involve monophthongs, diphthongs, and triphthongs. The speech data were analyzed by using KAY CSL 4100 (KAY Electronics). The data discussed in this study were testing items produced in citation form and sentence form, including the following syllable structures: CV, CVC, CVV, CVVC, and CVVV. The vowel qualities of Hai-lu Hakka vowels were measured and analyzed, and the acoustic vowel space of Hai-lu Hakka is plotted by the software Origin 6.0. Several results concerning the vowel quality of Hai-lu Hakka vowels were reported based on the formant frequency data. Firstly, there are six monophthongs in the vowel system of Hailu Hakka: [i], [e], [ɨ], [a], [o], and [u]. Secondly, there are eleven diphthongs in the vowel system of Hai-lu Hakka : [ie], [ia], [io], [iu], [eu], [ai], [au], [oi], [ui], [ue], and [ua]. By comparing the relative position of the vowel in a diphthong and the corresponding vowel as in a monophthong, we found that the second vowel in a diphthong tend to be higher or lower, more fontal or back, and it is possibly due to the coarticulatory influence of the adjacent phones.the Thirdly, as shown in the spectrogram of the three tripthongs [iai], [iau] and [uai], the duration of [i] in [iai55], [i] in [tʰiau55] and [u] in [kuai55] are relatively shorter than the rest two vowels in the same syllable, as [ai] in [iai55], [au] in [tʰiau55] and [ai] in [kuai55]. In these CVVV syllables, [u] and [i] are similar to glides or so-called semi-vowels, or approximants [j] and [w] as shown in the spectrogram. Finally, the vowel system in Yang (1957) is more suitable for accounting for the data in this study. Hopefully, the vowel formant data presented in this study will contribute to the study of vowels in Hakka.