The production of English monophthongs by Chinese Yi and Han speakers

Abstract

The English spoken in China is categorised within the Expanding Circle in the World Englishes paradigm. Of late, the diversity of Chinese dialects has drawn scholarly attention to China English accents. This study contributes to the existing literature on China English by focusing on the Sichuan province in southwestern China. It involves participants from the largest Han ethnic group and the Yi minority. English monophthongs produced by 40 Sichuan Han and Yi speakers were elicited, and their distribution and contrasts were examined and compared to provide insights into the production of their English vowels. Findings from the instrumental analysis indicate a lack of vowel-quality contrasts in specific vowel pairs produced by both Han and Yi speakers, resulting in a simplified vowel system. There are notable differences between Han and Yi speakers in the production of English vowels, possibly influenced by their different first languages. In addition, specific gender-based inconsistencies were also found, suggesting gender as an influencing factor in the production of English monophthong vowels. Overall, this study identifies Sichuan English as an emerging sub-variety of China English and supports the perspective that China English is an evolving and distinct variety rather than an interlanguage.

Introduction

Since China's first official foreign language school, the School of Combined Learning, was built in 1862, English has been taught in this vast and populous country for more than 160 years. It is estimated that between 200 and 400 million individuals in China have been learning English over the past few decades (Edwards 2017), while other studies such as Bolton and Graddol (2012) and He and Zhang (2010) suggest that the number of English learners and users in China ranges from 440 to 650 million (as cited in Edwards 2017). Regardless of the specific estimates, it is widely acknowledged in academia that China has a substantial base of English learners. The English spoken in China is categorised as being in the Expanding Circle within the World Englishes (WE) paradigm (Kachru 1985) due to its limited use in daily communication and transactions within the country and its status as a foreign language taught in schools.

At present, a variety of English accents exist in China, influenced by regional varieties of Mandarin and different languages like Cantonese, Hakka and Wu (Ao and Low 2012, 2016; Deterding 2006; Fang 2016; Zhang 2012, 2015). Thus, English language learners in China exhibit English accents with distinct regional characteristics due to the influence of their diverse linguistic contexts (Zhang 2015). Since Ge (1980) initially coined the term China English (CE), there has been a considerable amount of research into the various accents of this variety of English (e.g., Ao and Low 2016; Li and Sewell 2012). However, despite the diverse accents within CE produced by speakers from different ethnic groups (e.g., Han, Miao, Zhuang, Hui, Yi) and regions in China, the English pronunciation of Chinese speakers tends to be oversimplified and generalised into a broad category of Chinese-accented English (Huang and Hashim 2020).

Moving away from such generalisations, we focus on Sichuan, one of China's most multilingual and multicultural provinces. As the fifth most populous province, with a population of 83.67 million, Sichuan comprises the Han ethnic group and 55 other ethnic minorities (National Bureau of Statistics 2022). Recognising the complexity of Sichuan's sociolinguistic context, which is shaped by various sub-dialects and ethnic languages, it is important to note the phonetic differences between Mandarin and Yi. While Mandarin includes dorsal (tongue body) and apical (tongue tip) vowels, Yi is distinctive in having only ten dorsal and no apical vowels. Additionally, vowel length contrasts as a linguistic feature in Yi, which is absent in Mandarin, further complicates the influence on English pronunciation among Yi speakers (Ao and Low 2016; Ayu 2011).

The primary objective of this study is to examine the pronunciation features in Sichuan English (SCE) of two different ethnic groups, the Han and Yi, by focusing on the acoustic characteristics of the vowels. The research questions we sought to address were:

1. 1. What are the features of monophthongs produced by Sichuan Han and Yi male and female English speakers in terms of vowel quality?

2. 2. To what extent do these speakers contrast typical vowel pairs?

3. 3. To what extent does the production of English vowels by Yi speakers differ from Han speakers?

Previous studies

Over the past two decades, there has been an increasing amount of scholarly investigation on Chinese-accented English (Ao and Low 2016; Deterding 2006; Hung 2002; McLaughlin and Van Engen 2020). These studies have offered crucial insights into the emergence of a unique English variant within the Chinese context, thereby providing valuable references for studies on CE, including subsequent phonetic descriptions of CE. However, most studies primarily focused on delineating the general features of CE. There remains a significant lack of research specifically examining the pronunciation features reflecting regional and ethnic diversities, as well as an acoustic analysis of CE vowels, particularly among learners of English as a third language (L3) and the influence of Mandarin, regional dialects, and ethnic languages on their production.

Previous studies on CE vowels have proposed that their salient features are mainly due to the influence of their first language (L1), Mandarin (e.g., Chen 2006; Ho 2003; Yang and Fox 2014; Zhang 2018; Zhao et al. 2022). These studies have included the absence of differentiation between typical vowel pairs and the addition and reduction of vowels (Chen et al. 2001; Deterding 2006; Wang and Van Heuven 2006; Yang and Fox 2014). For example, Zhang (2018, 97-100) reported an ‘absence of length contrast in Chinese’ between pairs like /ɪ/ and /i:/, making them sound similar. This is consistent with the findings of Ho (2003). In addition, Chen et al. (2001) and Chen (2006) reported that the vowels produced by Mandarin speakers occur in a smaller vowel space and exhibit lesser acoustic diversity compared to American English speakers. Li (2019) also found that several CE vowels are produced with solid rhoticity in open syllables due to the influence of the speakers’ L1. For instance, China is often pronounced as [tʃaɪnɚ] and the is pronounced as [zɚ].

Ao and Low (2012) described several English vowel pronunciation features of Han (learning English as a second language or L2) and minority students (learning English as an L3) from the Yunnan province of China. Their findings indicated that these learners shared similar features such as /ʌ/ as [ɑ], the absence of reduced vowels, different realisations of the monophthongs /iː/, /ɪ/, /e/ and diphthongs /eɪ/, /ɑɪ/, /ɪǝ/. The speakers also inserted a schwa following word-final consonants (e.g., cat as [kætə]). However, Ao and Low (2012) do not explicitly mention whether these qualities are more specific to the Han and the minority languages. A subsequent study by Ao and Low (2016) found that Han speakers from Yunnan only distinguish the /ɪ/-/iː/ vowel pair and have more compact vowel spaces, unlike Yi speakers who differentiate long/short vowels in /ɒ/-/ɔː/ and /ʊ/-/uː/ pairs and have broader vowel spaces.

Within the context of SCE, there have been several studies about the acquisition and production of English vowels (Chen and van de Weijer 2018; Jin and Liu 2021; Lin and Wang 2019; Yun 2014). These studies have collectively focused on the influence of the Sichuan dialect on the acquisition and production of English vowels. However, ethnic variation among the population of L2 and L3 English learners in Sichuan has thus far not been considered in these studies. These studies also tend to be based on a perceptual examination of the vowels. Moreover, the influence of Mandarin alone or the combined influence of the L1 and L2 on their English pronunciation has not been considered. To start filling in these research gaps, the present study aims to investigate the production of eleven English monophthongs produced by Han and Yi English language learners from the Sichuan province. This study adopts the British English model, which includes eleven monophthongs, as the analytical framework. While learners in Sichuan are primarily exposed to British English through teaching materials and classroom instruction, it is acknowledged that American English influences may also exist through informal exposure, such as media.

Methods

To address the research questions, a total of 40 participants with intermediate-level English proficiency from different majors at a public university in the Sichuan Province were selected. They were divided into four groups of ten participants:

1. (i) 10 male Han L2 English learners

2. (ii) 10 female Han L2 English learners

3. (iii) 10 male Yi L3 English learners

4. (iv) 10 female Yi L3 English learners.

The participants had an average age of 19.5 years, with ages ranging from 18 to 22 years. The Han speakers typically acquire Mandarin as their L1 and English as their L2. Yi speakers generally learn the Yi language as their L1, with Mandarin as their L2 and English as their L3.

The participants had various academic backgrounds, possessed an intermediate level of English language proficiency. The Yi ethnic group was selected as they are the largest minority group in the Sichuan Province, with a population of 3.19 million as of 2022 (National Bureau of Statistics 2022). They also use their native Yi language. The Han participants were selected as they are the largest ethnic group in this province. The Research Ethics Committee of [Blinded University] approved this study, and a written informed consent was obtained from each participant.

A ZOOM H6 digital audio recorder was utilised to record the participants reading the test materials. The recordings were captured at 16-bit with a sampling rate of 44100 Hz (Asiaee et al. 2022). Each speaker recorded a total of 792 tokens. Before reading, participants had fifteen minutes to familiarise themselves with the target 11 words: ‘ship, sheep, bed, hat, hut, heart, pot, port, full, fool, bird’. They were instructed to read each word three times in the carrier sentence ‘Please say . . . again.’ at a steady pace (Pillai et al. 2010).

The target words were then annotated and measured using Praat Version 6.2.10 (Boersma and Weenink 2022). The target word and vowel were then segmented. The onset and offset of vowels were identified by visual inspection of the spectrograms and auditory judgements. Critical factors in this determination included the detectability of primary vowel formants and the existence of rhythmic energy (Derdemezis et al. 2016). The vowel segmentation and labelling underwent verification by two phoneticians for accuracy and consistency. The frequencies of the first formant (F1) and the second formant (F2) of the vowels were measured at the midpoint of the vowel, while the duration was measured from the onset of the offset of the vowel (see Figure 1). Because the measurement of formant frequencies can be affected by neighbouring consonants, the formant values were captured at the midpoint of the target vowel (see Watt and Tillotson 2001, 277), as this is the time when a vowel is thought to be the most stable and least impacted by any sounds coming before or after it (Pillai et al. 2010), such as the stop consonants in this context.

Figure 1. Sample annotations and measurement in Praat.

Two Praat scripts (Formant Script and Durations Script) (Lennes 2017) automatically generated the F1, F2, and durational data from the labelled Textgrid files. Extreme measurements were subsequently checked using Praat's ‘get formant’ function. The average F1 and F2 values of speakers were then calculated, and the resulting formant values were transformed into a Bark scale using Zwicker and Terhardt's (1980, p. 1524) formula:

Z = 13arctan(0.00076 F)+3.5arctan(F/7500)²

Euclidean distances of the central vowel were also measured. This technique, previously utilised by Deterding (2009) and Ao and Low (2016), determines the average distance between the centroid and all vowel plots. It also evaluates the centrality or peripherality of vowels within the vowel quadrilaterals of speaker groups. Statistical analysis was carried out using SPSS (26.0 version). The short-long ratio of vowel pairs was determined by comparing the average duration values of the monophthong vowels as produced by the participants. To investigate any significant differences in the duration of the two vowels in five pairs of short and long vowels, the research used two-tailed t-tests. The analysis focused on the distinctions between male and female speakers within each ethnic group, as well as the F1 and F2 of vowels produced by Sichuan Han and Yi English learners.

Results

Vowel quality

Figure 2 presents the overall vowel chart of the 11 monophthongs produced by the SCE speakers, where a notable lack of distinction between the vowel pairs /ɪ/-/iː/, /ʌ/-/ɑː/, /ɒ/-/ɔː/, and /ʊ/–/uː/ can be observed. This results in a reduced inventory of vowels in comparison to, for example, the standard spoken variety of British English. This discovery is consistent with findings from previous studies on CE pronunciation (Ao and Low 2016, 2012; Wang 2022).

Figure 2. Mean formant plot for SCE vowels¹.

Table 1 displays the average F1 and F2 measurements and the Euclidean distance for the Sichuan Han and Yi English speakers, respectively. The comparison of the mean formants of the vowels produced by the Sichuan Han speakers reveals a convergence between the vowel pairs /ɪ/-/iː/, /ʌ/-/ɑː/, /ɒ/-/ɔː/, and /ʊ/-/uː/. This convergence is particularly evident with /ɪ/ and /iː/. As expected, paired sample t-test results show no significant differences between /ɪ/-/iː/ (F1: t[19]=−.412, p=.685, d=−.092; F2: t[19]=−.643, p=.528, d=−.144) and /ʊ/-/uː/ (F1: t[19]=−.684, p=.502, d=−.153; F2: t[19]=1.109, p=.281, d=.248). However, for the vowel pair /ʌ/-/ɑː/, a significant difference was found in F1 (t[19]=2.751, p<0.05, d=.615), but not in F2 (t[19]=−.136, p=.893, d=−.03). For /ɒ/-/ɔː/, no significant difference was found in F1 (t[19]=1.177, p=.254, d=.254), but a significant difference was found in F2 (t[19]=2.824, p<0.05, d=.631).

Table 1. Mean values for monophthong vowels’ F1, F2, and Euclidean distance (ED) of Sichuan Han and Yi speakers

In contrast, the vowel /e/ and /æ/ were distinguished with statistically significant differences between the average F1 and F2 values: F1 (t[19]=−4.077, p<0.001, d=−.912), F2 (t[19]=3.282, p<.05, d=.734). Similarly, for the Yi speakers, there were statistically significant differences between /e/-/æ/ (F1: t[19]=−5.119, p<0.001, d=−1.145; F2: t[19]=4.126, p<0.001, d=0.923). And for the vowel pair /ʌ/-/ɑː/, a significant difference was found in F1 (t[19]=2.485, p<0.05, d=0.556), but not in F2 (t[19]=0.013, p=0.99, d=0.003). However, unlike the Han speakers, the Yi also displayed significant differences in the vowel pair /ɒ/-/ɔː/ (F1: t[19]=−4.222, p<0.001, d=0.637; F2: t[19]=3.773, p<0.001, d=0.491). There were no significant differences in the vowel pairs /ɪ/-/iː/ (F1: t[19]=1.654, p=0.115, d=0.37; F2: t[19]=0.538, p=0.597, d=0.12) and /ʊ/-/uː/ (F1: t[19]=0.614, p=0.547, d=0.137; F2: t[19]=0.83, p=0.417, d=0.186) produced by Yi speakers. In terms of the Euclidean Distance (ED), no statistically significant differences were found between Han and Yi ethnic groups in terms of their Euclidean distance through an independent t-test (t[18]=−.224, p=.825, d=−.100). This finding indicates that the sizes of the vowel spaces for the Han and Yi groups were similar.

Figure 3 illustrates overlaps between the vowels produced by the Han speakers and those produced by the Yi speakers. This overlap can be observed for the high front vowels /ɪ/, /iː/, and the high back rounded vowels /uː/. The difference between the two groups lies in the placement of the mid-central vowel /ʌ/ and the open-back vowel /ɑː/. Han speakers tend to articulate these two vowels in a more anterior position compared to Yi speakers.

Figure 3. Formant plots of vowels produced by Sichuan Han and Yi speakers.

Gender differences in vowel quality among the two ethnic groups

Figures 4 and 5 present formant plots illustrating the similarities and differences in formant values across categories. Figure 4 shows that, for most vowels, male Yi language speakers tend to have a more forward articulation than their Han counterparts, except for the vowels /ɜː/, /ʌ/, and /ɑː/. Additionally, compared to male Yi speakers, male Han speakers demonstrate a greater distance between the vowels in each pair /ʌ/-/ɑː/ and /ʊ/–/uː/ when distinguishing them. However, they demonstrate a reduced distinction between the vowel pairs /ɪ/-/iː/ and /ɒ/-/ɔː/, showing closer proximity and even some overlap between the pairs.

Figure 4. Formant plots of vowels produced by Sichuan male Han and Yi speakers.

Figure 5. Formant plots of vowels produced by Sichuan female Han and Yi speakers.

On the other hand, Figure 5 demonstrates that the eleven monophthongs articulated by female Han speakers exhibit more fronting than those by male Yi speakers. In terms of vowel pair differentiation among the female Han and Yi speakers, it is observed that the differences between /ɪ/-/iː/ and /ʌ/-/ɑː/ are not obvious, while the differences between /ɒ/-/ɔː/, /ʊ/-/uː/, and /e/-/æ/ are apparent. Female Han speakers demonstrate a greater distance between the vowels in the pairs /ɒ/-/ɔː/ and /ʊ/-/uː/, while female Yi speakers demonstrate a more significant distinction between /ɪ/-/iː/ and /e/-/æ/. Furthermore, when contrasted with Figure 4, it becomes apparent that both female Han and Yi speakers show fewer overlaps and more significant distinctions in all vowel pairs compared to their male counterparts except for /ɪ/-/iː/ and /e/-/æ/.

Vowel duration

In terms of durations of vowel pairs /ɪ/-/iː/, /ɒ/-/ɔː/, /ʌ/-/ɑː/, and /ʊ/-/uː/, both the Han and Yi groups generally maintain durational differences across the vowel pairs /ɒ/-/ɔː/ (Han: t[19]=−4.002, p<0.001, d=−.895; Yi: t[19]=−3.64, p<0.01, d=−.815) and /ʊ/-/uː/ (Han: t[19]=−3.359, p<0.01, d=−.751; Yi: t[19]=−3.554, p<0.01, d=−.795). Han speakers showed more contrast between /ɪ/-/iː/ (t[19]=−2.45, p<0.05, d=−.548, and /ɒ/-/ɔː/ (t[19]=−2.45, p<0.05, d=−.548). In contrast, Yi speakers exhibited wider separations in the pairs /ʌ/-/ɑː/ (t[19]=−4.048, p<.001, d=−.905) and /ʊ/-/uː/ (t[19]=−3.554, p<0.01, d=−.795). However, no significant differences were found between the durations of /ɪ/-/iː/ among Yi speakers (t[19]=−1.821, p=.084, d=−.407) and /ʌ/-/ɑː/ for Han speakers (t[19]=−2.507, p=.054, d=−.46).

Upon analysing the mean duration of vowel pairs among four distinct groups: male Han, female Han, male Yi, and female Yi speakers, it becomes evident that there are notable differences in their ability to discriminate between vowel pairs. Specifically, male Han speakers demonstrate difficulty in differentiating between /ɪ/-/iː/ (t[9]=−2.038, p=.072, d=−.645) as well as /ʌ/-/ɑː/ (t[9]=−1.229, p=.25, d=−.389), yet they exhibit a capacity to distinguish /ɒ/-/ɔː/ (t[9]=−2.65, p<0.05, d=−.838) and /ʊ/-/uː/ (t[9]=−2.317, p<0.05, d=−.733). Similarly, female Han speakers fail to differentiate /ɪ/-/iː/ (t[9]=−1.644, p=.135, d=−.52) and /ʌ/-/ɑː/ (t[9]=−2.016, p=.075, d=−.638), but they can discern /ɒ/-/ɔː/ (t[9]=−2.897, p<0.05, d=−.916) and /ʊ/-/uː/ (t[9]=−2.427, p<0.05, d=−.767). Male Yi speakers, on the other hand, cannot differentiate /ɪ/-/iː/ (t[9]=−1.586, p=.147, d=−.502) and /ʊ/-/uː/ (t[9]=−1.674, p=.129, d=−.529), whereas they are successful in distinguishing /ʌ/-/ɑː/ (t[9]=−2.836, p<0.05, d=−.897) and /ɒ/-/ɔː/ (t[9]=−2.996, p<0.05, d=−.947). Finally, female Yi speakers are unable to differentiate /ɪ/-/iː/ (t[9]=−1.02, p=.334, d=−.322) and /ɒ/-/ɔː/ (t[9]=−2.12, p=.063, d=−.671), yet they exhibit a capacity to discriminate /ʌ/-/ɑː/ (t[9]=−2.74, p<0.05, d=−.866) and /ʊ/-/uː/ (t[9]=−3.519, p<0.01, d=−1.113).

Discussion

In terms of vowel quality, compared to Standard British English, Sichuan Han and Yi English speakers produced a smaller inventory of English monophthong vowels. This feature is due to the lack of contrast between the vowel pairs /ɪ/-/iː/, /ʌ/-/ɑː/, /ɒ/-/ɔː/, and /ʊ/–/uː/. Unlike British English's ‘scattered’ vowel distribution, their pronunciation featured a more ‘clustered’ vowel chart. This finding aligns with previous studies on CE (Ao and Low 2012; Deterding 2006; Hung 2002) as well as with other varieties from the Expanding Circle (e.g. Russian English, Japanese English, Korean English) and the Outer Circle (e.g. Indian English, Nigerian English, Malaysian English) within the World Englishes paradigm (Kachru 1985).

Sichuan Han and Yi speakers also showed similarities in vowel space. Specifically, they produced high front vowels /ɪ/, /iː/, and high back rounded vowels /uː/ in a similar manner. Furthermore, no statistically significant difference was found between the Han and Yi ethnic groups regarding the vowels’ Euclidean distance. This similarity could be attributed to their originating from the same region. Sichuan Mandarin, with its pronunciation features from both Mandarin and the Sichuan dialects, may have influenced the pronunciation patterns of these speakers and likely played a significant role in shaping their vowel production. Consequently, despite their different linguistic backgrounds, the shared regional dialect partially unified their vowel articulation.

Beyond these specific vowels, both Han and Yi speakers showed minimal variation in their monophthong vowel articulations, indicating a close resemblance in their pronunciation. The similarities might have stemmed from the shared language education context and dialects among Han and Yi English speakers. However, a significant difference was found in the vowel height of /ɒ/ and /ɔː/. In addition, the vowel articulatory position for vowels /e/-/æ/ and /ɒ/-/ɔ/ were also notably different. The placement of the mid-central vowel /ʌ/ and open-back vowel /ɑː/ was also different, with Han speakers showing the tendency to articulate the two vowels more anteriorly than Yi speakers. This finding echoed the results of the Han and Yi English major groups in the study by Ao and Low (2016). The reason might have been that Mandarin includes dorsal (tongue body) and apical (tongue tip) vowels, while the Yi language has ten dorsal vowels and does not have apical vowels (Yang 2014). This distinction might have influenced the vowel production of Yi L3 English speakers.

In relation to vowel duration, the variations in the production of English monophthongs by Sichuan Han and Yi speakers indicated that their different first languages might have influenced their production of these vowels. Yi speakers demonstrated extended durations when articulating long-short vowel pairs, likely due to the phonetic influences of their mother tongue. Yi language has unique vowel articulations and durations that contrast with Mandarin. While Mandarin does not inherently possess vowel length contrasts, Yi speakers’ native language includes such distinctions, thus possibly influencing their perception and production of L3 English vowels (Ayu 2011; Yang 2014).

The Han speakers were found to exhibit more significant distinctions in discriminating between the vowel pairs /ɪ/-/iː/ and /ɒ/-/ɔː/, whereas Yi speakers demonstrated more significant differences in the vowel pairs /ʌ/-/ɑː/ and /ʊ/-/uː/. These findings were partially consistent with the study by Ao and Low (2016). For example, the Yi speakers differentiated /ʊ/-/uː/ better than the Han speakers. This variation might be due to the influence of their different L1 s on their vowel production, affecting these specific vowel articulations. In addition to the impact of L1 linguistic or demographic variables on English vowel pronunciation, learners’ difficulties or failures in pronouncing certain monophthong vowels might have stemmed partly from inadequate instruction or practice in English teaching or learning processes. This is because not all learners with similar linguistic backgrounds encounter the same pronunciation issues with certain monophthongs.

However, more participants from both groups and additional measurements of each vowel pair were needed to further validate these explanations. The influence of first languages on foreign language pronunciation had been well documented in various studies, such as Carlson et al. (2016) and Derwing and Munro (2005). Since different first languages had different influences on the production of another language, the findings of this study illuminated the production of English monophthong vowels by speakers from the same region but with different language backgrounds. In this case, Yi speakers spoke Yi as their first language, Mandarin (standard and local Sichuan dialects) as their second language, and English as their third language. On the other hand, Han speakers spoke Mandarin as their first language and learned English as a foreign language.

Apart from the first language, gender was also found to influence a speaker's production of sounds. In this study, upon analysing the duration of vowel pairs among four distinct groups – male Han, female Han, male Yi, and female Yi speakers – it became evident that there were notable differences in male and female Yi speakers’ ability to discriminate between vowel sounds. Specifically, there was a lack of contrast between /ɪ/-/iː/ and /ʊ/-/uː/ among male Yi speakers, but they could distinguish /ʌ/-/ɑː/ and /ɒ/-/ɔː/. There was a lack of distinction between /ɪ/-/iː/ and /ɒ/-/ɔː/ among female Yi speakers, but they could differentiate between /ʌ/-/ɑː/ and /ʊ/-/uː/. These differences might have been attributed to gender differences in auditory processing and language experience of Yi speakers (Yang 2014).

Conclusion

This study examined the qualities and durations of 11 monophthong vowels in Sichuan with samples from 40 Han L2 and Yi L3 speakers. Notable differences were found in their ability to discriminate vowel sounds. Han speakers, including both males and females, articulated /ʌ/ and /ɑː/ more anteriorly and demonstrated a lack of vowel contrast between the vowel pairs /ɪ/-/iː/ and /ʌ/-/ɑː/, but they could differentiate /ɒ/-/ɔː/ and /ʊ/-/uː/. On the other hand, Yi speakers exhibited different patterns, with male Yi speakers showing a lack of vowel contrast for the vowel pairs /ɪ/-/iː/ and /ʊ/-/uː/, while female Yi speakers demonstrated a lack of vowel contrast for /ɪ/-/iː/ and /ɒ/-/ɔː/. Both Han and Yi speakers generally maintained durational differences across the vowel pairs /ɒ/-/ɔː/ and /ʊ/-/uː/, with Han speakers showing more significant differences for /ɪ/-/iː/ and /ɒ/-/ɔː/, while Yi speakers showed more considerable differences for /ʌ/-/ɑː/ and /ʊ/-/uː/.

There were also specific gender-based inconsistencies in differentiating the duration of certain vowel pairs. Female Han and Yi speakers displayed more vowel quality contrast than their male counterparts. In addition, male Yi speakers showed a lack of durational contrast for /ɪ/-/iː/ and /ʊ/-/uː/, while female Yi speakers demonstrated a lack of distinction for /ɪ/-/iː/ and /ɒ/-/ɔː/ though both can distinguish /ʌ/-/ɑː/ and /ʊ/-/uː/.

Overall, this study underscores the lack of vowel-quality contrasts in specific pairs and the significant influence of first language and gender on English vowel production among Sichuan Han and Yi speakers. The differences found in vowel production between Han and Yi speakers highlight SCE's unique phonological patterns. However, the focus on intermediate-level speakers indicates the need for future research to include a more diverse participant base and to analyse diphthongs for a more comprehensive view of the SCE vowel system. Despite its limitations, this research lays the foundation for further exploration of CE phonological variations using instrumental methods. By identifying traits such as a simplified vowel system and notable differences in vowel length, this study shows SCE as an emerging sub-variety of CE and supports the perspective that CE is an evolving and distinct variety rather than an interlanguage. Future research with a broader participant base and additional phonetic features will further validate and enhance our understanding of CE.