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             \author[1]{Opeyemi Emmanuel,  Olawe}

             \affil[1]{  University of Nigeria}

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\date{\small \em Received: 5 September 2021 Accepted: 4 October 2021 Published: 15 October 2021}

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\begin{abstract}
        


This study examined the production of English vowels by Yoruba-English bilingual undergraduate students at the University of Nigeria, Nsukka. The instrument used for data collection was the pronunciation of a prepared word list. Sixty (60) students who speak Yoruba as their first language were randomly selected from five departments. The bilingual status of the students made it possible to assemble a corpus which reveals their various levels of competency in English. The result of the findings indicate that Yoruba language vowels differ to a large extent from English language and due to this, there are certain variations and deviations in the realization of English vowels by Yoruba-English bilingual students. From the data gathered, analysis shows that we do not have an equal number of vowels in both languages and there are some vowels in Yoruba that are not present in the English language.

\end{abstract}


\keywords{contrastive analysis, vowels, english, yoruba, students.}

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\let\tabcellsep& 	 	 		 
\section[{Introduction}]{Introduction}\par
oday, English has become the leading language of the world, spoken and understood in most parts of the globe. While it is the mother tongue language in some places, it has been adopted as the second and official language of many countries in the world. In Nigeria, English is spoken as the second language and the official language used in government, media, business, law, education and so on. The important role English language plays makes it mandatory for anybody who wants to be relevant in his society or see beyond his horizons to learn and use the language effectively. Resultantly, the English language is a compulsory subject, studied as a second language and used as the medium of instruction and communication in all educational institutions in Nigeria.\par
As stated by \hyperref[b12]{Tsojon and Aji (2014)}, pronunciation is a vital aspect of language learning as poor pronunciation distorts or mars the communication process. In the same vein, Al-Saidat (2010) asserts that the ultimate goal of most second language learners is to attain native-ever, for many learners in Nigeria, this has not been easy especially in the area of stress placement and timing, intonation control and most especially, the wrong pronunciation of words. In the opinion of \hyperref[b5]{Chitulu and Njemanze (2015)}, this is because of the fact that learners have to grapple with a lot of factors-his mother tongue, teacher-induced errors, apathy to language learning, peer group pressure, and many other factors. These phenomena have not placed the Nigerian student on a good pedestal to communicate in the English language.\par
Pronunciation is by far one of the several problems affecting most people learning English as a second Language (L2) in Nigeria \hyperref[b12]{(Tsojon and Aji, 2014)}. Students are not able to produce correct forms of sound in the target language which hinders effective communication. This could be that the knowledge of their first languages generally interferes with their usage of the English language or the differences that exist between the mother tongue language and the second (target) language pose a barrier to their English pronunciations.\par
Ogbuehi (2003) asserts that every normal child acquires the sound system and the speech patterns of his mother tongue in a normal way through imitation of sounds from adult groups. On the other hand, learning to speak a second language or foreign language usually involves some rigours and challenges because the learner has to learn the sound systems and the prosodic features of the second language against the already firmly consolidated first language in the mind of the learner. The adjustment to these differences may lead to a mismatch and therefore, the learner may produce sounds that cannot be understood by other users of the same language.\par
Since each language has its own unique peculiarities and any learner learning the language must be able to master the peculiarities of the language learnt, it is unfortunate that many Nigerian second language learners are unable to adjust successfully to the speech habit of the English language because the knowledge of the mother tongues often interference in the phonological realization of English sounds (Awa and Nwani-Grace, 2018).\par
The difference in the phonology of English and that of most Nigerian languages is wide. Take for example, the Yoruba language which is one of the Nigerian languages estimated by \hyperref[b13]{Wikipedia (2020)} to be spoken between 40 to 50 million people, most of whom live in Nigeria. When the comparison between the sound system of the English and Yoruba languages are examined, there are unique differences between the two languages. Yoruba has some speech sounds that are unfamiliar to English and vice visa. It then predicts that the differences between the two languages' phonemes may lead to pronunciation difficulty for Yoruba learners of English (Patrick, Sui, Didam and Gyang, 2013). Dairo (2008) maintains that some sounds (phonemes) in the English language which are not in the inventory of learners' mother tongue are often pronounced as perceived to them, substituting it with the most similar sound existing in their first language. This substitution of phonemes from mother tongue to second language creates many problems for the learners of English as a second language.\par
As the phonological system of Yoruba is contrasted with that of English, there is a need to compare and contrast the sound structure of both languages in order to establish how the similarities and differences interfere in spoken English of Yoruba-English bilingual students. Hence, this study is aimed at exploring the vowels of English and Yoruba as articulated by Yoruba bilingual undergraduate students at the University of Nigeria, Nsukka. 
\section[{II.}]{II.} 
\section[{Objectives of the Study}]{Objectives of the Study}\par
The work specifically intends to: i. Examine the production of English vowels by Yoruba-English bilingual undergraduate students of the University of Nigeria, Nsukka. ii. Find out how learners' knowledge of Yoruba vowels impedes the pronunciation of Yoruba-English bilingual students of the University of Nigeria, Nsukka. 
\section[{III.}]{III.}\par
Literature Review on English and Yoruba Vowels  
\section[{b) English and Yoruba Vowels Compared}]{b) English and Yoruba Vowels Compared}\par
As seen above, the English language has a total of 20 vowels. Out of these, 12 are pure vowels and eight are diphthongs. The English 12 pure vowels comprise of 7 short vowels: /i/, /e/,/ae/,/?/, /?/, /?/, /?/ and 5 long vowels: /i:/, /a:/, /É?":/, /?:/, /u:/. On the other hand, there are 7 oral vowels /I, e, ?, a, o, É?", u/ and 5 nasalized vowels / ? ? ã ? É?"? ? / in Yoruba. The vowel sounds /i, e, u, É?", and a/ are similar in both languages while the three English central vowels: /?, ?, ?:/ are non-existent in Yorùbá.\par
Nasalization is a contrastive or distinctive feature in Yoruba that is not recognized in English. Unlike English which doesn't nasalize its vowels, Yoruba has five nasal vowels which are nasal counterparts of five out of seven oral vowels. According to Brain Tiffen (1974), in Yoruba orthography, nasalised vowels are usually indicated by a vowel + 'n', which sometimes causes speakers to carry over this convention into English. Thus 'dance' may be pronounced as /dã:s/.\par
Both English and Yoruba oral vowels can occur at word-initial, word-medial and word-final positions. Still, words usually end, if not in all cases, in vowel sound unlike English where words can either end in vowels or consonants. This can be seen in words like ile (house) oko (farm) eegun (masquerade), igbadun Free variation is allowed in English sounds where the vowel /i/can be substituted for /e/ without necessarily changing the meaning of the words. This can be seen in words like neither (naið.? /ni:ð.?), direct (d?'r?kt/di'r?kt/dai'r?kt), economy (I'kÉ?"n.?.mi/e'kÉ?"n.?.mi), finance (fai.naens/fi:naens), examinations (ig.zaemi' nei??n/eks.zaemi'nei??n) and many more but in Yoruba, substituting any of the vowels leads to a change in meaning as seen in Ile (house) and Il? (land), oko (hoe) and ?k? (hushand). There is distinction in the sounds and cannot be substituted for the other, else, the meaning is either changed or distorted. "They are therefore called vowel phonemes" (Bankole, 2019).\par
(enjoyment); even English words that are either borrowed or loaned into Yoruba do ends in vowels. Vowels /u/ and /i/ are at the end of words like /kobodu/ for "cupboard", /koopu/ for "cup", /flaski/ or /filaski/ for flask, /girini/ for "green", /pinki/ for pink, ayoonu for Iron, hosipitu for Hospital. "Class" is spelt and pronounced as/kilasi/. The vowel /i/ is inserted between the consonant clusters /k/, ditto the consonant /l/ is dropped in the pronunciations of 'school" /sukulu/ and "principal" /prinsipa/, etc. This is because Yoruba words hardly ever end in consonants but vowels \hyperref[b11]{(Tijani, 2015)}.\par
Long vowels occur in Yoruba but have no phonemic status. There is the absence of distinctions of vowel length in Yoruba. As argued by Akinjobi (2004) cited in Bankole (2019), vowel lengthening in Yoruba is often a result of an optional pattern of deletion as in the contrast between 'egungun/eegun' (masquerade), "agogo and aago" (bell) and /da:da / from the word 'daradara' "very good" where the deletion of /r/ in fast speech leads to the emergence of [?:] which is interpretable as /a/ + /? /. Therefore, the five long vowels of English don't exist in Yoruba, just as there are no closing and centering diphthongs in Yoruba. This means that diphthongs or even triphthongs are not found in Yoruba, although the sequences /ai/(Taiye) and/au/ (Ausa/wal'nut) occur, but equivalents to RP/ei/ and/au/ do not. Centering diphthongs have no equivalent in Yoruba  {\ref (Brain, 1974)}.\par
Due to the phonological differences that occur between English and Yoruba sounds, the Yoruba native learners of English will have to learn the habit of pronouncing these somewhat strange sounds which pose some difficulties to Yoruba speakers of English language.\par
IV. 
\section[{Theoretical Framework}]{Theoretical Framework}\par
This study was analyzed using Contrastive analysis Theory. 
\section[{a) Contrastive Analysis Theory}]{a) Contrastive Analysis Theory}\par
Contrastive analysis is concerned with a systematic comparison of a pair of languages with the purpose of bringing to light their phonological, morphological, syntactic and lexical differences and similarities. Contrastive analysis is a method that is used to find out and explain why some features of a foreign language were more difficult to learn than others. Learners' first language will not be difficult to learn but when the learner comes in contact with another language, he/she will discover some features of it far easy to learn and others excessively difficult. Thus, in Contrastive Analysis (CA), it is assumed that learning a second language is facilitated whenever there are similarities between that language and mother tongue (Nwabudike, Kaan, and Anaso, 2015). \hyperref[b8]{Lado (1957)} in Awa and Nwani-Grace (2018) says that those elements of a foreign language similar to the learner's native language will be simple for the learner to learn. Whereas, those elements of a foreign language that are different from the learner's native language will be difficult for him/her to acquire. According to  {\ref Dulay and Burt (1977)}, second language learning difficulty result from interference from old habits in the learning of new habits. Therefore the old habits are those of the first language while the learnt habits are those of the second language. The greater the differences between the two languages the greater the difficulty and more errors will be made.\par
Using this theory is important for this study since it sought to establish whether phonological differences between mother tongue and second language, consciously or unconsciously influence the performance of English in the context under study. The study followed the procedures of Contrastive Analysis for making systematic comparison and contrast of any two languages. The steps are: Selection -descriptioncomparison -prediction -verification.\par
The first step is to select or take the two languages, L1 and L2. The selection has to be limited to a specific category because it will be difficult to compare everything (sound, word, structure, etc). In the second step which is description, the study chose English and Yoruba Vowels as what to be contrasted/compared after which the Vowels were linguistically described with a focus on the differences. Thirdly, having described the linguistic-selected units, a comparison of the vowels with each language was made. This step is called 'comparison'. Step four which is 'prediction' is about predicting difficulty through contrast. Linguistic believe that when the structures of the set of two languages are similar, positive transfer will occur while with those that are different, a negative transfer will take place. In this study, the researcher tested the problems students encounter due to the differences in the English and Yoruba vowels through the pronunciation of listed words. Through this, the researcher was able to attest to the problems students face as a result of the difference.\par
V. 
\section[{Empirical Review}]{Empirical Review}\par
Many works have been done on the problems Nigerian speakers of English face in their pronunciation due to interference of Nigerian languages. Here are a few of them.\par
In the study of Keshavarz and Khamis (2017) which investigated the pronunciation problems of Hausa speaking learners of English, sixty male Hausa-speaking students were randomly selected as the sample from three universities in Northern Cyprus. The participants were all raised in Hausa-speaking communities in Nigeria where there is not much interaction with native or non-native speakers of English in society or workplace. Questionnaire and pronunciation test were used as the instruments for collecting data. The participants were asked to read aloud English words and sentences and describe the pictures containing problematic English sounds while being audio recorded. As illustrated in the findings of the study, errors in the pronunciation of all four English consonants (i.e., /?/, /ð/, /f/, and /v/) have a high percentage of occurrence; the vowel /?:/ has the highest percentage of occurrence (91.7\%), followed by /?:/ (86.6\%) and /?/ (76\%). The reason for such mispronunciation is the difference between the inventory of English and Hausa consonants and vowels.\par
Tsojon and Aji (2014) examined the problems among Jukun (Wapan) speakers of English. The study provided information on why problems occur and the specific English phonemes that Wapan speakers of English find difficult to pronounce or articulate. Data were collected through participant observation of utterances of one hundred native speakers who were considered educated in relative to the degree of communicative competence in English. These native speakers who were randomly selected were also asked to read a list of English words to determine their levels of proficiencies in pronunciation. The study revealed that pronunciation problems among the people are largely due to the mother-tongue influence as many English phonemes do not exist in Wapan. \hyperref[b6]{Dairo (2008)} in his work "A Polylectal Approach to the Study of Phonological Interference in Yoruba English'' discussed the factors within the learner and the environment that contribute to faulty speech performance of Yoruba learners of English. Samples of students' speeches from three major dialect groups: Oyo, Ondo and Ekiti were examined. The study concluded that all Yoruba speakers of English, irrespective of their linguistic background, make similar substitutions for the problematic sounds in English and the absence of certain sounds in Yoruba always causes problems for Yoruba speakers of English.\par
In the studies reviewed above, it was shown that contract in English and other Nigerian indigenous languages is the major source of problem and pronunciation difficulty that many Nigerian speakers of English face. However, only a few work have been specifically done on the similarities and differences between the vowels of English and Yoruba and their effects on the students' pronunciation. This is why this study is undertaken. 
\section[{VI.}]{VI.} 
\section[{Methodology}]{Methodology}\par
In this study, a quantitative method of research design was adopted. Quantitative type, according to Bankole (2019), is the design that deals with figures and descriptive type of analysis which is particularly valuable in providing in-depth rich data. This research design is appropriate to the study because data generated from the research were descriptively analyzed without manipulation or distortion of variables.\par
All Yoruba-English bilingual students in five departments whose mother tongue was the Yoruba language in the University of Nigeria, Nsukka constituted the population of the study. The study used both purposive and random sampling techniques to select participants from the five departments. A purposive sampling technique was used to select students who speak Yoruba as their first language. They speak and understand both English and Yoruba. Yoruba is the students' L1 while English is their L2. Simple random sampling was then employed to select ten (10) Yoruba bilingual students each from the five selected departments, making a total of fifty students from the university.\par
A prepared word list containing vowels and consonants of English was given to each respondent to pronounce. This word list, comprising thirty-four words was validated by experts in the field of phonology to determine how much the items measured the objective intended to measure. The participants were asked to read while being audio recorded. The recorded data were analyzed after listening to each participant's pronunciation a few times, paying particular attention to the realization of English vowels. Using International Phonetic Alphabet (IPA), utterances were phonemically transcribed and then compared with the target language norm in order to determine the correct and incorrect pronunciation of English vowels and the interferences in the pronunciations. 
\section[{VII.}]{VII.} 
\section[{Results and Discussion}]{Results and Discussion}\par
In this section, the data collected was analyzed using contrastive analysis theory. Having selected English and Yoruba Vowels as the point of contraction, the vowels of the two languages were described and compared to attest to the likely problems that the contract poses to Yoruba bilingual students. The data gathered through the pronunciation of prepared word lists were analyzed to respond to the research questions. Different realizations of vowels by the respondents were presented alongside the RP of Standard English vowels. The data and analysis are presented below: a) Production of English Vowels by Yoruba-English Bilingual Undergraduates of University of Nigeria, Nsukka 
\section[{Words}]{Words}\par
Yoruba Pronunciation RP			\footnote{A Contrastive Analysis of the Production of English and Yoruba Vowels by Yoruba-English Bilingual Students in the University of Nigeria, Nsukka} 		 		\backmatter  			 \par
These words were mispronounced due to the silence of some letters in words. As seen in the pronunciation of 'vowel', students pronounced the silent /w/ in their realization ditto 'corps' and 'sachet' when the consonant cluster '-ps' and '-t' respectively are silent. Plumber was also pronounced as written; unconscious that "b" is not voiced, distorting the meaning C. Incorrect pronunciation of /?, ?, ?:/ which are absence in Yoruba Language The Yoruba language has fewer vowel sounds than the English language. Since some vowels of English are lacking in the Yoruba language, the Yoruba bilingual respondents replace the absent sounds with the nearest sound to it or Yoruba phonemes based on the similarity of the sounds. The three vowels: /?, ?, ?:/ which are absent in Yoruba was realized and replaced with /? and ae/ respectively. Respondents take the sound nearest to the given sound from the Yoruba sound inventory and replace it with what they have on paper and then pronounce it.  
\subsection[{Money}]{Money} 
\subsection[{Conclusion}]{Conclusion}\par
The present paper has attempted to assess the vowels of English and Yoruba languages by focusing on the similarities and differences. This study shows that there is a significant difference between the vowels of English and Yoruba counterpart which often lead to phonological interferences in the spoken utterances of students. The majority of the students simply substitute English sounds that are absent with Yoruba equivalence. This often negates standard pronunciation and localize their realization of English sounds as they often pronounce silent letters in words, realize diphthongs as pure vowel, and substitute central vowels of English which are non-existent in Yoruba for Yoruba equivalents.\par
This interference even at the tertiary level could be said to be due to inadequate mastery of English phonemes. If at the tertiary level, they make these mistakes, then, correction of these errors from childhood education is the only lasting solution. It is expedient for students to be taught the sound system of English and Yoruba and their correct pronunciation right from the primary school level. This is because at the primary level, it is much easier to learn pronunciation effectively and often difficult to learn after this time. When students are exposed to the sound system of the two languages at the early stage, they will be able to distinguish the phonemes of the two languages. With the teaching of English and Yoruba sounds intensified at the early level of education, the students will certainly have some knowledge of the two languages by the time they get to the university. Consequently, differences in the two languages will not present a problem. Also, teachers in primary and secondary schools even teachers in tertiary institutions need to be models for correct pronunciation. If students listen to correct pronunciation from all their teachers, unconsciously, they will internalize the correct sound patterns and this problem of pronunciation would be reduced to the barest minimum.			 			  				\begin{bibitemlist}{1}
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