Acoustic Correlates of Vowel Intrusion in the English of Educated Hausa Speakers

By

¹ Dr. Sadiya Abubakar Gwandu & ²Dr. Halima Abdullahi Aminu

¹Department of European Languages and Literary Studies, Federal University Birnin-Kebbi, Kebbi State, Nigeria

²Department of English Language and Linguistics, Sokoto State University, Sokoto, Nigeria

Corresponding Author’s email & Phone No: sa.gwandu@fubk.edu.ng 08060151527

Abstract

This study investigates the acoustic characteristics of vowel intrusion in the English of educated Hausa speakers. Vowel intrusion, a form of epenthesis, is commonly employed to resolve consonant clusters that are incompatible with Hausa syllable structure.  Previous studies have described this phenomenon, yet, there is limited empirical research examining its acoustic realisation. Drawing on insights from acoustic phonetics which are grounded in Interlanguage Theory, this study adopts a mixed-methods approach. Data was collected from 10 educated Hausa English speakers through word lists. Acoustic analysis was conducted using Praat to measure formant frequencies (F1, F2) and duration of intrusive vowels. The study aims to identify the phonological environments that trigger vowel intrusion, determine the quality and consistency of inserted vowels. Findings are expected to demonstrate that vowel intrusion is systematic and phonetically measurable rather than random error, reflecting L1 transfer. The study contributes to research on Nigerian English phonology and provides empirical support for the integration of acoustic methods in the study of second-language phonological processes.

Keywords: Acoustic, Correlates, Vowel, Educated, Hausa and Speakers

Introduction

The study of second-language phonology has consistently demonstrated that speakers tend to restructure unfamiliar phonotactic patterns to conform to the constraints of their first language. Within phonology, one of the most widely observed strategies is vowel intrusion (epenthesis) the insertion of a vowel to break consonant clusters that are disallowed in the speaker’s L1.

Hausa, like many Chadic languages, predominantly favours open syllable (CV) structures, making consonant clusters in English problematic. As a result, Hausa speakers of English often produce forms such as school → [sukul] or strike → [sitiraik]. While earlier studies have described such patterns impressionistically, there is a growing need to examine them using instrumental and acoustic methods.

Recent advances in acoustic phonetics have shifted attention toward the fine-grained measurement of speech features, including vowel quality (F1, F2), duration, and intensity. However, there remains a paucity of detailed acoustic studies on epenthesis in Nigerian English varieties, particularly among educated Hausa speakers, whose speech reflects both proficiency and localized phonological patterns.

This study, therefore, seeks to provide an acoustic account of vowel intrusion, contributing to broader discussions in second language acquisition and aligning with Interlanguage Theory, which conceptualizes such features as systematic and rule-governed rather than erroneous.

Statement of the Problem

Despite the recognition of vowel intrusion in Hausa English, existing studies are largely impressionistic rather than instrumentally verified, focused on error description rather than phonological patterning and silent on the acoustic properties of intrusive vowels.  Furthermore, little attention has been paid to how vowel intrusion persists among educated speakers, raising questions about: its systematicity and phonetic realization 

This gap limits our understanding of how L1 phonological constraints interact with English phonotactics in educated Hausa speakers speech.

 Aim and Objectives of the Study

The aim is to investigate the acoustic characteristics of vowel intrusion in the English of educated Hausa speakers. The Objective is to analyze the acoustic properties (F1, F2, duration) of intrusive vowels. The Research Question is what are the acoustic characteristics of intrusive vowels in Hausa English?

Literature Review

Vowel epenthesis is considered to be a phonological process used in the adaptation of loanwords in languages (Cain 1986; Park 1987; Akinlabi 1993; Mwihaki 2001; Uffmann 2002; Kenstowicz 2007; Adomako 2008). Languages with restrictions on syllable structure permit vowel epenthesis in order to satisfy these restrictions when dealing with borrowing words from other languages (Uffmann, 2006). Consider the following examples, the bold letters are the epenthetic vowels inserted:

 (1) Vowel epenthesis in loanwords:

Yoruba kíláàsi ‘class’ (Akinlabi, 1993), Kikuyu ngirathi ‘glass’ (Mwihaki, 2001), Japanese sutoraiku ‘strike’ (Park,1987), Samoan sikauti ‘scout’ (Cain, 1986), Fijian sipiiniji ‘spinach’ (Kenstowicz, 2007), Akan sutɔpu ‘stop’ (Adomako, 2008), Shona gi.ri:ni ‘green’ (Uffmann,2002)

Mufleh & Rebecca (2015) discussed vowel epenthesis as a phonological process utilised to avoid codas in Arabic loanwords in Hausa language in light of Optimality Theory (OT), even though Hausa permits codas in heavy syllables of the form CVC (Caron, 2013). This process results in having disyllabic, trisyllabic, or quadri-syllabic words depending on the forms of Arabic loanwords as well as mono-syllabic words with final bi-consonant clusters. The study majorly relies on extant literature and the authors’ intuition was crucially deemed to judge on the facts of the data. The paper concludes that codas in Arabic loanwords in Hausa motivate vowel epenthesis either once or twice, depending on the forms of words; i.e., disyllabic or monosyllabic. Also, the number of vowel insertion depends on the number of consonants in the coda position, i.e., /CVCC/→ vowel epenthesis→ [CVC.CV] or [CV.CV.CV], as exemplified below:

(2) Arabic loanwords of the form CVCC in Hausa

 a. /dars/→ [da.ra.si] ‘a lesson’ [CV.CV.CV]

 b. /ħarf/→ [ha.ra.fi] ‘a letter’ [CV.CV.CV]

c. /ʤamʕ/→ [ʤam.ʔi] ‘plural form’ [CVC.CV]

Hausa Syllable Structure

The Hausa language permits three primary syllable structures, as identified by Jaggar (2001) and Caron (2013):

(3) Examples of these structures are as follows:

a)      CV – as in ni (‘me’), sha.re (‘sweep’)

b)      CVV – as in faa.ɗo (‘fall’), zau.na (‘sit’), ɗau.ko (‘bring’)

c)      CVC – as in can (‘there’)

According to Sani (2005), Hausa syllables can be classified into open and closed types: Open syllable consists of a consonant followed by a vowel (CV or CVV), where the vowel may be short, long, or a diphthong. Closed syllable is formed by a consonant followed by a short vowel and a final consonant (CVC). Each syllable consists of three components: onset (initial consonant(s)), nucleus (vowel or syllabic element), and coda (final consonant(s), if present).

(4) Illustrative examples include:

a)      ci (CV) – ‘eat’, b) waje (CV.CV) – ‘outside’, c) jii, kai, yau (CVV) – ‘hearing’, ‘head’, ‘today’, e) biyar (CV.CVC) – ‘five’ and nan (CVC) – ‘here’

Hausa tends to favour disyllabic, trisyllabic, or quadrisyllabic words. While monosyllabic words do occur, they are mainly limited to function words (e.g., pronouns, connectors) and a small number of ideophones or monosyllabic verbs (e.g., bi – ‘follow’, jaa – ‘pull’).

Theoretical Framework

This study is anchored in Selinker (1972) Interlanguage Theory, which posits that second-language learners develop a systematic linguistic system influenced by both L1 and L2. Selinker (1972) hypothesises that there is a latent psychological structure in the brain which is activated when one tries to learn a second language after already acquiring proficiency in a first language. For instance, the utterances and expressions produced by a second language learner would be neither the first nor the second language. That is to say, a second language learners’ speech would not be identical to that produced by the native speakers of the target language, and nor would they be exact translation of the target language. Instead, a separate linguistic system would be developed. The processes of interlanguage are dynamic and developmental; thus, represent the transitional competence of a second language learner. Thus, it is these interlanguage processes that are specific to individuals that would be taken into consideration when analysing the data collected from the participants.

The framework is complemented by Phonological Transfer Theory (L1 influence on L2 structures), by Lado’s (1957) Contrastive Analysis Hypothesis, which explains that learners transfer phonological features from their first language into a second language. Together, these perspectives allow vowel intrusion to be interpreted not as random error, but as a structured, meaningful phonological process.

Methodology

This paper adopts a mixed-method design, combining both quantitative and qualitative techniques. It also employs a descriptive approach. The quantitative dimension involves measuring the frequency of occurrence of the phonological processes under investigation, while the qualitative aspect provides interpretive insights into these patterns and complements the quantitative findings.

The study population comprises educated Hausa speakers of English residing in Sokoto State, Nigeria, including both male and female participants. The classification aligns with Jibril’s (1986) model of Nigerian English speakers, which categorises speakers primarily by educational status. Educated speakers are linguistically stable, so deviations reveal interlanguage features rather than lack of education. To ensure reliability, objectivity, and feasibility, a purposive sampling technique was employed. This technique enabled the researcher to select participants who met specific criteria, including educational qualification, age, and gender.

The source of data for the study is primary, as data was obtained through audio recordings of a word-list reading task. This method aligns with Labov’s (1966) assertion that word lists are particularly effective in phonological research, as they present a uniform set of linguistic variables to all participants. This consistency enhances the formality of responses and allows for direct comparison across subjects. The word list was designed to systematically elicit occurrences of epenthesis in controlled linguistic contexts. The decision to utilise a word-list reading task, rather than spontaneous speech, aligns with Labov’s (1966) argument that controlled linguistic tasks are effective in eliciting specific phonological variables.

A total of ten (10) undergraduate participants, five (5) males and five (5) females were purposively chosen. The participants were drawn from Sokoto State University. The age range considered was: 20–30 years. The stimuli consist of 40 words targeting epenthesis, participants read the word-list and their pronunciations were recorded using an OLYMPUS MP3 digital recorder. The recordings served both as empirical data and as verifiable evidence of the study’s authenticity. Below are the stimuli given to the participants:

Table 1: Stimuli on Epenthesis

1.      Bread	11.Problem	21. Critical	31. Pronunciation
2.      Splash	12. Plastic	22. Principle	32.Congratulations
3.      Glass	13. Signal	23. Production	33. Matrimonial
4.      Class	14. English	24. Attribute	34.Controversial
5.      School	15. Transfer	25.Description	35. Grammatical
6.      Broom	16. Ignore	26. Projector	36. Administrator
7.      Pray	17. Printer	27.Graduation	37. Spectacular
8.      Play	18. Player	28. Practical	38. Propaganda
9.      Print	19. Traffic	29. Primary	39. Proletariat
10.  Glow	20. Standard	30.Conclusion	40. Matriculation

To ensure systematic interpretation of the data, the recordings obtained from participants were repeatedly reviewed, and relevant phonological phenomena were transcribed using the International Phonetic Alphabet (IPA). To enhance reliability, a colleague verified the transcriptions to ensure inter-rater agreement. Subsequently, the data were subjected to acoustic analysis using Praat software (Boersma & Weenink, 2024), which facilitated the visualisation and measurement of acoustic properties such as segment duration. Praat enabled the researcher to precisely detect vowel insertions, thus, providing empirical backing for the perceptual analysis.

Data Presentation and Analysis

The data collected from the participants on the occurrence of epenthesis are presented. The table represents the realisation of the stimuli given to the participants; serial number (S/N), correct realisation (CR), epenthetic realisation (EPR) percentage (%) and total score, hence presented:

Table 2: Occurrence of Epenthesis in the English of Educated Hausa Speakers (Undergraduate)

S/N	CR	%	EPR	%	T	%
1	13	32.5	27	67.5	40	100
2	25	62.5	15	37.5	40	100
3	12	30	28	70	40	100
4	30	75	10	25	40	100
5	18	45	22	55	40	100
6	26	65	14	35	40	100
7	19	47.5	21	52.5	40	100
8	29	72.5	11	27.5	40	100
9	36	90	4	10	40	100
10	23	57.5	17	42.5	40	100

The above data shows the occurrence of epenthesis in the English of educated Hausa speakers based on the level of education of the participants who are undergraduate. In table 2:1, the participant made 32.5% correct realisation with 67.5% in epenthetic forms. In 2:2, the participant correctly realised the stimuli with 62.5% and 37.5% were in epenthetic forms. In 2:3, 30% correct realisation were made by the participant and 70% were in epenthetic forms. In 2:4, 75% correct realisation and 25% epenthetic realisation were recorded from the participant. In 2:5, 45% correct realisation and 55% epenthetic realisation were successfully obtained. In 2:6, the participant recorded 65% correct realisation, and 35% pronunciation with epenthetic realisation. In 2:7, the participant made an average correct realisation of the stimuli with 47.2% and 52.5% in epenthetic realisation. In 2:8, the participant made 72.5% correct realisation and 27.5% epenthetic realisation. In 2:9, the participant made 90% correct realisation only 10% of the words were realised in epenthetic forms. In 2:10, 57.5% of the stimuli are correctly realised and 42.5% in epenthetic forms.

Discussion of the Result

The chart above indicates that epenthetic realisations accounted for 57.25% among undergraduates. The results indicate a significant prevalence of epenthesis in the English of educated Hausa speakers. This phenomenon can be attributed to the phonological disparities between Hausa and English. Acquisition of a second language involves mastering both segmental and suprasegmental features.

This study sought to determine the occurrence of vowel epenthesis in the English of educated Hausa speakers, a phenomenon indicative of suprasegmental interference. The results reveal that various vowels are inserted in particular phonological environments to align with the Hausa syllable structure (CV, CVV, and CVC). Fluent learners produced fewer epenthetic vowels, irrespective of age, or gender.  Gender-wise, epenthetic insertions were recorded in both male and female participants, as can be seen in table 2:3 and 2:6. Schmitt (2010) supports the notion that L1 continues to influence L2 acquisition, regardless of gender.

In conclusion, the data confirm that participants exhibited traits consistent with interlanguage (Selinker, 1976), such as simplification of L2 structures and transfer of L1 features. While epenthesis may not be phonemic, it significantly alters word perception, often rendering speech alien to native listeners.

Sample of Instrumental Analysis from the Participants

Received Pronunciation (RP) furnishes the reference model against which learner productions are evaluated. Side‑by‑side inspection of the RP signal and each participant’s signal allows a fine‑grained comparison of segmental cues, and prosodic contours. It is important to know the acoustic features of the inserted vowels /ʊ/ and /ɪ/. Articulatory Description of /ʊ/, height: High (but slightly lower than /uː/), backness: Back (sometimes near-back), roundedness: Rounded lips, Tenseness: Lax, Length: Short. Acoustic Features of /ʊ/

Acoustic Parameter	Typical Value/Behavior
Formant 1 (F1)	Low: Around 300–450 Hz, due to high tongue position
Formant 2 (F2)	Low: Around 800–1200 Hz, due to back tongue position
Formant 3 (F3)	Varies, often around 2400–3000 Hz
Duration	Short: Around 75–150 milliseconds
F1-F2 Gap	Narrower gap than front vowels like /ɪ/
Amplitude	Moderate to low intensity due to tongue position and lip rounding
Spectral Quality	Lower overall energy compared to unrounded front vowels
Formant Transitions	Smooth and quick when transitioning to adjacent consonants

F0        -          Fundamental Frequency

F1        -          First Formant

F2        -          Second Formant

F3        -          Third Formant

Figure 1. RP Realisation of the word ‘School’

Clear periodic wave pattern during the vowel /uː/ portion (voiced). The waveform is relatively clean and consistent with a native fluent production. High-frequency energy above 3000 Hz, typical of voiceless fricatives. Then, /k/, there is brief silence, followed by a burst. /uː/ formant structure visible with high F1-F2 distance, suggesting a close back rounded vowel. there is an /l/   visible formant transitions at the end with a reduction in energy, consistent with a syllable-final lateral approximant. Pitch (blue line) is relatively stable, peaking slightly during the vowel /uː/. Pitch drops towards the coda consonant /l/. Intensity (Green line) Smooth intensity rise and fall, peaking around the vowel normal for a stressed syllable. Entire word segment lasts 0.56 seconds, indicating normal tempo. Below is a participant’s realisation of the stimuli

Figure 2. Realisation of the word ‘School’ by an Undergraduate Participant

The waveform indicates two strong vocalic peaks, reflecting the syllables: /sʊ/, /kuːl/. Initial segment /s/ displays low amplitude and turbulent aperiodic waveform consistent with voiceless frication. Vowels /ʊ/ and /uː/ show increased amplitude, reflecting full voicing and syllabic energy. /k/ has a distinct closure burst between the two vowel peaks, indicating full articulation. Final /l/ also shows a voiced segment but with slightly lower amplitude than the preceding vowel. Formant Patterns and Voicing; /s/ clear high-frequency frication above 4000 Hz, visible as a band of aperiodic noise. /ʊ/ rounded, high back vowel with F1 around 400–600 Hz and F2 around 900–1200 Hz. /k/ clear closure and burst visible in the spectrogram, indicating a well-articulated voiceless velar stop. /uː/ a high, back vowel with low F1 and lower F2 than /ʊ/, consistent with lip rounding and tongue retraction. /l/ appears with low-frequency energy (often below 1000 Hz), particularly in F2 and F3 regions. Pitch (blue contour) rises gradually during the first syllable /sʊ/ and falls slightly during /kuːl/. Intensity (green contour) shows two peaks highest on /uː/, indicating stress placement on that syllable. The pitch range remains relatively compressed, possibly reflecting flat prosody or cautious articulation.

L1 Influence Hausa disallows initial consonant clusters like /sk/, often inserting a transitional vowel to repair illegal syllable onsets. The vowel [ʊ] may be selected as a compromise between phonetic ease and vowel availability in Hausa.  The praat picture below presents the RP realisation of the word ‘Critical’.

Figure 7. RP Realisation of the Word ‘Critical’

To analyse the word ‘Critical’, it shall be good to know the acoustic features of the inserted vowel. The short vowel /ɪ/ has distinct acoustic features that set it apart from other vowels. It is different from the long tense vowel /iː/ (as in "beet"), particularly in terms of duration, formant values, and tenseness. Articulatory Description of /ɪ/, High front vowel, Lax (less muscular tension), Unrounded, Short in duration. Typically produced with the tongue near the front and high in the mouth but slightly lower and more centralised than /iː/

 Acoustic Features of /ɪ/

Feature	Description
Formant 1 (F1)	Low F1: around 300–450 Hz, indicating a high tongue position
Formant 2 (F2)	High F2: around 1800–2100 Hz, indicating a front tongue position
Formant 3 (F3)	Often above 2500 Hz, though less distinctive
Duration	Shorter than /iː/, typically 75–150 milliseconds in connected speech
Amplitude	Moderate amplitude, less intense than tense vowels
Formant transitions	Smooth transitions into and out of neighboring consonants; useful for identifying surrounding place of articulation
Spectral quality	Clear formant structure, especially the F1-F2 gap, but with a slightly centralised vowel space compared to /iː/

On a Praat spectrogram, you would typically see:

        i.            Two clear formant bands (F1 and F2)

      ii.            F1 low and F2 high, forming a wide space between them

    iii.            Shorter time duration along the x-axis

    iv.            Less intensity compared to /iː/

 The RP realisation has the syllables /krɪ/ | /tɪ/ | /kəl/, no epenthetic vowel, the /kr/ cluster is preserved, showing smooth consonant transition without inserted vowel. Final syllable realised with a schwa /ə/, typical of RP in weak syllables.  Syllabic /l/, that is, the final /l/ in /kəl/ is syllabic as the /ə/ and /l/ are merged acoustically, with weak energy in the vowel region. Smooth and natural contours, indicative of fluent native-like articulation.  Accurate consonant clusters, proper segment duration and natural rhythm.  The compressed timing, particularly of weak syllables, is characteristic of RP’s stress-timed rhythm. Number of syllables 3, Stress-timed with primary stress on /krɪ/. 

Figure 8. Realisation of the Word ‘Critical’ by an Undergraduate Participant

The waveform shows multiple voicing peaks, each corresponding to a syllable boundary. Energy is generally higher on the vowels (especially /iː/ and /a/), which carry the syllabic nuclei. The presence of several voiced segments suggests a more syllable-timed rhythm rather than the stress-timed nature of RP. Voiceless consonants like /k/ and /t/ show reduced amplitude and sharp transitions, as expected. /k/: clear stop closure and release; visible as a brief silence followed by a burst. /ɪ/ and /iː/: front vowel formants visible; /iː/ has a lower F1 and higher F2, indicative of its tense and high-front quality. /r/: formants are transitional, with lowered F3, suggesting rhoticity. /t/: well-articulated stop, although possibly lengthened due to segmentation. /a/: low vowel with widely spaced F1 and F2 (indicative of central or back vowel positioning). /l/: voiced lateral approximant with low-frequency energy concentration below 1000 Hz. The vowel [iː] occurs twice, showing that the speaker introduced an epenthetic or lengthened vowel between consonants, which is non-canonical. The pitch contour (blue) shows multiple rises and falls, suggesting a more level, syllable-by-syllable intonation. This deviates from RP prosody, which would show stress on the first syllable and more reduced subsequent syllables. Intensity (green) peaks align with the longer vowels, particularly /iː/ and /a/, suggesting misplaced or redistributed stress. Voiceless consonants (e.g., /k/, /t/) show intensity dips as expected. Visible segment duration approximately 0.65milliseconds (from 1.297026s to 1.944629s). Full pronunciation covers more syllables than expected for RP total of six syllables instead of the canonical three. Each syllable is relatively equal in duration, showing reduced vowel reduction, which is typical in L1 interference patterns.

The results obtained from the participants indicate that, in words such as /sku:l/ and /krɪtɪkəl/, participants inserted an epenthetic vowel to conform to the Hausa CV syllable structure, rendering the words as /sʊku:l/ and /kɪri:tɪkɑl/, respectively. These findings are consistent with Selinker’s (1972) Interlanguage Theory, which posits that second language learners develop an intermediate linguistic system influenced by their native language. This study accentuates the persistent influence of Hausa phonology on English pronunciation and emphasizes the need for targeted pedagogical strategies to enhance intelligibility in English spoken by Hausa speakers.

Conclusion

In conclusion, the presence of epenthesis indicates transfer of training from Hausa phonotactics. A minority of participants demonstrated native-like proficiency, suggesting that complete acquisition of a second language without noticeable interference is possible, although rare. Variation in outputs despite identical stimuli indicates that interlanguage is unique to each speaker, reinforcing Selinker’s (1972) assertion of interlanguage as highly individualised.

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This article is published in ALQALAM: A Journal of Language and Literary Studies, FUGUS, Volume 1, Issue 2 - June 2026