Every language has its own characteristics. It also brings its uniqueness that is not owned by other languages. Indonesia has more than 600 different languages called mother tongues bounded by Indonesians. Mother tongue refers not only to the language one learns from one's mother but also the speaker's dominant and home language which is called native language.
Learning mother tongue is started from one's home. Mother tongue will be one's habitual language if it is used frequently in family and society. In fact, for some urban young generation nowadays do not recognize their mother tongue. As a millennium generation, they think globally as the effect of nowadays information which is mailed into English.
English as EFL is familiar to Indonesia as first EFL taught in schools. Those whose mother tongue is their daily language, it will interfere English pronunciation. Indonesians would pronounce past as /p a:st/ without aspiration as in Indonesian word pagi because /p/ is not aspirated in all position. There is possible phonemic negative transfer between languages and it can make weird.
The mother tongue users will encounter some common difficulties when pronouncing the English's words. Brown (2007) stated that factors that cause the difficulties are phonological differences between their native language (L1) and their second language/foreign language (L2).
Batak Toba, one of the ethnics in Indonesia, has a unique language and culture. Batak Toba dialect reflects the sounds in foreign language such as English. Once, a Batak-Toba adult pronounced bird as /birt/. He got difficulty to pronounce some sounds in term of English vowel sounds. It is highlighted that the Batak Toba-neses experience mispronunciation of English vowel sounds.
All native speakers whose English is not their mother tongue will bring their mother tongue-like accent to the English pronunciation. Due to the different phonological system between Batak Toba language and English such problem arises. It is observed that mother tongue-like accent interferes the English pronunciation. It is difficult for Batak Toba-neses whose English is their foreign language to speak with native-like pronunciation. Batak Toba-neses bring their different accent freely from their native-like accent in pronouncing English, then their English pronunciation sounds awkward. Therefore this study attempts to identify the mispronunciation of English vowel sounds produced by Batak Toba-neses. It discusses about how Batak Toba-neses pronounce the English vowel sounds and how mother tongue-like accent affects the English vowel sounds.
It is believed that the aim of the research will be very useful to enrich the concept of phonological system of different languages. Known that mother tongue-like accent interferes the English pronunciation, therefore the nature of this research is to highlight the area of phonological divergence between Batak Toba language and English. Finally, it is important to know how Batak Toba-neses pronounce the English vowel sounds and to find out the English vowel sounds whose the Batak Toba-neses mispronounce.
2. Literature Review
English vowel sounds
Brown (2007) found that an ESL or EFL learner meets some difficulties, because his L1 affects his L2 especially in adulthood, and this effect is a result of L1 transfer; so it is a significant source of making errors for ESL or EFL learner. Carter & Nunan (2001) showed that mother tongue has clear influence on learning L2 pronunciation. While mother tongue-like accent interferes the English pronunciation, phonology deals with one' s knowledge of the sound system of a language, then it concerns with a competence.
English phonology is divided into two branches; segmental phonology and suprasegmental phonology . Segmental phonology is based on the segmentation of language into individual speech sound provided by phonetics. Segmental phonology concerns with the function and possible combination of the sounds within the sound system (Skandera and Burleigh in ). Suprasegmental phonology is connected within those features of pronunciation that cannot be segmented because they extend over more than one segment or sound. Its features include stress rhythm, and intonation. Concerning about the segmental features, English vowel sounds are the area to be discussed in this theory (Skandera and Burleigh in .
Finegan (2015) explains vowel sounds are produced by passing air through different shapes of the mouth with different position of the tongue and the lips and with the air stream relatively unobstructed by the narrow passages except at the glottis. Connor in  mentions that vowel can be described with vowels placement called cardinal vowel diagram.
Batak Toba language
Batak Toba langauge is the oldest langauge of all mother tongues in Nort Sumatera . Batak Toba language also has unique vowel sounds. /e/ is familiar in Batak Toba vowel sound but not for /Z:/ or /ә/ or another soft pronouncing. Batak Toba language also has consonant, vowel, and diphthong sounds like English but some sounds are different.
Batak Toba language has /i/, /e/, /ʌ/, /o/, and /ʊ/ sounds. Those vowels are classified into front vowel, central vowel, back vowel, high vowel, low vowel, and mid vowel. Below is the way how the Batak Toba language vowel sounds are pronounced.
Sound /ʌ/, The word aha (what) is pronounced as /ʌ' hʌ/
Sound /i/, The word itok (brother) is pronounced as /i' tok/
Sound /ʊ/, The word unang (do not) is pronounced as /ʊ' nʌŋ/
Sound /e/, The word eta (let's go) is pronounced as /e' tʌ/
Sound /o/, The word olo (yes) is pronounced as /o' lok/
Kozok (1999) also explains in his book about Batak Toba language alphabets and sounds that it is called Surat Batak
3. Research Method
This is a descriptive qualitative research because it concerns with the natural context of the adult Batak Toba-neses' pronunciation. Creswell (2012) mentions that a qualitative research is concerned primarily with process, meaning, and understanding rather than outcomes and procedures. A qualitative research needs to report faithfully the realities and to rely on voices and interpretation of informants. Descriptive research is designed to obtain information concerning with the current status of phenomena. The aim of descriptive study is to describe what exist with respect to variable or condition in a situation.
The respondents of the research are taken by using purposive sampling technique in which the 20 males and 20 females Batak Toba-neses aged 20 to 40 years old. They were born in North Sumatera. They are workers and students. Their education background is senior high school graduates in North Sumatera. The respondents live in Batam. Based on the interview, they use Batak Toba language for their communication at home and with their friends the same ethnic.
Observation method is applied in collecting data using the technique of involved conversation observation . There was an open-ended Interview session of the respondents to know the respondents' background . It was applied to provide useful and detail information. The respondents are asked to pronounce the words eat, it, get, mat, car, put, saw, dog, two, cut, bird, and ago after showing them correct pronunciation based on the standard of Received Pronunciation (Oxford Dictionary). Technique of recording is used to collect the data.
Then, the data is analyzed by using the method of articulatory phonetic identity proposed by Sudaryanto (2015). This method is used to find out the mispronunciation of English vowel consonants. Equalizing technique proposed by Sudaryanto (2015) is used to equalize the Batak Toba-neses' pronunciation with correct pronunciation based on the standard of Received Pronunciation (Oxford Dictionary). Finally, competence in equalizing the main point technique is the technique to know the competence of Batak Toba-neses in pronouncing the given English words as a final result of analyzing.
There are 20 males and 20 females Batak Toba-neses pronounced the words eat, it, get, mat, car, put, saw, dog, two, cut, bird, and ago that represent the sounds /i:/, /ɪ/, /ʊ/, /u:/, /e/, /ə/, /з:/, /ɔ:/, /æ/, /ʌ/, /ɑ:/, and /ɒ/. With the same background of education, place of birth, and the mother tongue usage, they have mostly the same similarities and differences in pronouncing the English vowel sounds.
Eleven male Batak Toba-neses were not able to pronounce the sound /i:/ in eat. They pronounced /i:/ as /ɪ/, meanwhile the nineteen female Batak Toba-neses were not able to pronounce the sound /i:/. On the other hand, the male and female Batak Toba-neses were able to pronounce the sound /ɪ/ in it. The sound /ɪ/ exists in Batak Toba language pronunciation.
All male Batak Toba-neses were able to pronounce the sound /e/ in get. Two female Batak Toba-neses were not able to pronounce the sound /e/. The male and female Batak Toba-neses were able to pronounce the sound /e/ in get. The sound /e/ exists in Batak Toba language pronunciation.
The male and female Batak Toba-neses were not able to pronounce the sound /æ/ in mat. There is not the sound /æ/ in Batak Toba language pronunciation. Seven male and nine female Batak Toba-neses were not able to pronounce the sound /ɑ:/ in car. The sound /ʊ/ in put were pronounced correctly by fourteen males and sixteen females Batak Toba-neses. The sound /ʊ/ was easily pronounced by the respondents because the sound /ʊ/ exists in Batak Toba language pronunciation.
Twelve male and eighteen female Batak Toba-neses were not able to pronounce the sound /ɔ:/ in saw. But almost all male and female Batak Tobe-neses were able to pronounce the sound /ɒ/ in dog and two male and female Batak Toba-nese were not able to pronounce it. The sound /ɒ/ exists in Batak Toba language pronunciation.
The sound /u:/ in two was pronounced incorrectly by four male and one female Batak Toba-neses. The sound /u:/ is familiar to the Batak Toba-neses. There is the sound /u:/ in bu. The pronunciation of Indonesian influences to Batak Toba-neses' pronunciation.
The sound /ʌ/ in cut is also familiar to the Batak Toba-neses. Three male and four female Batak Toba-neses were not able to pronounce the sound /ʌ/. The respondents pronounced /ʌ/ incorrectly because they pronounced cut as /tʃʊt/ and /kʊt/.
Finally, the seventeen male and eighteen female Batak Toba-neses were not able to pronounce the sound /з:/ in bird and seventeen male Batak Toba-neses were not able to pronounce the sound /ə/ in ago. They pronounced ago as /ʌgɒ/ and /egɒ/. All female Batak Toba-neses were able to pronounce the sound /ə/. As the pronunciation of Indonesian influences to Batak Toba-neses' pronunciation, there is the sound /ə/ in kepada, keluarga, kejut, kemiri, kedua and so forth.
Mostly the Batak Toba-neses pronounced the long vowel sounds incorrectly such as /i:/, /з:/, /ɔ:/, and /ɑ:/
• All the respondents are not able to pronounce the sound /æ/ in mat.
• The respondents pronounce mat as /mʌt/ and /met/.
• All the respondents are not able to pronounce the sound /з:/ in bird.
• The respondents pronounce bird as /birt/, /bert/, and /bi:rt/.
• The sound /i:/ in eat and /ɔ:/ in saw are pronounced incorrectly by the female more number than the male Batak Toba-neses.
• The respondents pronounce saw as /sʌw/ and /sɒw/, meanwhile they pronounce eat with the short /i/.
• Almost all of the male Batak Toba-neses are not able to pronounce /ə/ in ago and all female Batak Toba-neses are able to pronounce /ə/.
• The male Batak Toba-neses pronounce ago as /egɒ/.
• The language contact influences the female Batak Toba-neses due to the word kepada, keluarga, kejut, kemiri, and kedua in which vowel e is pronounced as /ə/.
• The respondents are not too difficult to pronounce the sound /ɑ:/ in car.
• Sound /ɑ:/ exists in Indonesian and Batak Toba language with no long sound.
• Sound /u:/ is not difficult to be pronounced by the respondents
• Sound /u:/ is influenced by the Indonesian word bu as /bu:/.
• Sounds /ʊ/, /ʌ/, /ɒ/, /e/, and /i/ are pronounced correctly by the respondents because these sounds appear both in Indonesia and Batak Toba languages. And, these sounds are the based vowel sounds of Indonesia and Batak Toba languages.
• Additionally, Batak Toba language vowel sounds do not produce long intonation sound but it can be adapted by the respondents.
• The respondents treat the English vowel sounds as the same with their mother tongue vowel sounds.
• Comparing between male and female Batak Toba-neses' way of English pronuncing, female is more adaptable in pronouncing the foreign language in term of English (EFL) than the male is.
This paper has concluded the area of English vowel sounds where the adult Batak Toba-neses do not pronounce English words correctly, due to the mother tongue-like accent interference. The mother tongue like-accent is able to affect the ability to pronounce foreign language words. The Batak Toba-neses are not able to pronounce a few English vowel sounds. It is caused by the difference of phonological system.
By the use of mother tongue or native language as a home language will form the speaker's speech organ system as well as the native-accent and mother tongue-accent. Toba Surat Batak describes that Batak Toba language has five main vowel sounds /i/, /e/, /ɒ/, /ʌ/, and /ʊ/, batak toba-neses are not able to pronounce the English vowel sounds /æ/, /з:/, and /ɔ:/ as these sounds do not exist in Batak Toba language. Batak Toba-neses are able to pronounce the English vowel sounds /i/, /e/, /ɒ/, /ʌ/, and /ʊ/ correctly.
The English vowel sounds /i:/ and /ɑ:/ are not pronounced correctly as they are long vowel sounds. Mostly Batak Toba language has short vowel sounds. The English vowel sounds /ə/ and /u:/ are able to be pronounced correctly because these sounds exist in Indonesian such as ke /kə/ and bu /bu:/.