$\mathbb{P}\left(\lvert\widehat{P}^{o}_{h,s,a}\nu-P^{o}_{h,s,a}\nu\rvert\geq\epsilon\right)\leq
2\mathrm{exp}\left(-\frac{2N\epsilon^{2}}{\nu_{\max}^{2}}\right)=2\mathrm{exp}\left(-\frac{2N\epsilon^{2}}{\left(\frac{H(B_{p}+\rho^{p})}{\rho^{p}}\right)^{2}}\right),\qquad\forall\epsilon>0.$

Now recall that
$\left\lvert\mathcal{N}_{\rho,V}(\theta)\right\rvert\leq\frac{HB_{p}+(H\vee\rho^{p})}{\rho^{p}\theta}$
and choose

$\epsilon=\frac{H(B_{p}+\rho^{p})}{\rho^{p}}\sqrt{\frac{\mathrm{log}\left(2\left\lvert\mathcal{N}_{\rho,V}(\theta)\right\rvert/\delta\right)}{2N}}.$

We then have

$\displaystyle\mathbb{P}\left(\left\lvert\widehat{P}^{o}_{h,s,a}\nu-P^{o}_{h,s,a}\nu\right\rvert\geq\frac{H(B_{p}+\rho^{p})}{\rho^{p}}\sqrt{\frac{\mathrm{log}\left(\frac{2HB_{p}+2(H\vee\rho^{p})}{\rho^{p}\theta\delta}\right)}{2N}}\right)$
$\displaystyle\qquad\qquad\qquad\qquad\leq\mathbb{P}\left(\left\lvert\widehat{P}^{o}_{h,s,a}\nu-P^{o}_{h,s,a}\nu\right\rvert\geq\frac{H(B_{p}+\rho^{p})}{\rho^{p}}\sqrt{\frac{\mathrm{log}\left(2\left\lvert\mathcal{N}_{\rho,V}(\theta)\right\rvert/\delta\right)}{2N}}\right)$
$\displaystyle\qquad\qquad\qquad\qquad\leq\frac{\delta}{\left\lvert\mathcal{N}_{\rho,V}(\theta)\right\rvert}.$

Finally, applying a union bound over $\mathcal{N}_{\rho,V}(\theta)$, we get

$\max_{\nu\in\mathcal{N}_{\rho,V}(\theta)}\lvert\widehat{P}^{o}_{h,s,a}\nu-P^{o}_{h,s,a}\nu\rvert\leq\frac{H(B_{p}+\rho^{p})}{\rho^{p}}\sqrt{\frac{\mathrm{log}\left(\frac{2HB_{p}+2(H\vee\rho^{p})}{\rho^{p}\theta\delta}\right)}{2N}},$

with probability at least $1-\delta$. Combining the above and Eq. 36 completes
the proof. ∎

###### Proof of Proposition 9.

Recall that $\widehat{V}_{h+1}$ is independent of $\widehat{P}^{o}_{h,s,a}$ by
construction. Similar to Corollary 1 and Proposition 2, the result directly
follows from Lemma 18 and the law of total probability. ∎

We now have all the ingredients to prove our main result.

###### Proof of Theorem 5.

The proof is almost identical to that of Theorem 1. By applying Proposition 9
and taking a union bound over
$(h,s,a)\in[H]\times\mathcal{S}\times\mathcal{A}$, we have

$\left\lVert
V_{1}^{*}-V_{1}^{\widehat{\pi}}\right\rVert_{\infty}\leq\frac{2H^{2}(B_{p}+\rho^{p})}{\rho^{p}}\sqrt{\frac{\mathrm{log}\left(\frac{2H\left\lvert\mathcal{S}\right\rvert\left\lvert\mathcal{A}\right\rvert(HB_{p}+(H\vee\rho^{p}))}{\rho^{p}\theta\delta}\right)}{2N}}+4H\theta$

with probability at least $1-\delta$. We can choose $\theta=\epsilon/(8H)$.
Note that since $\epsilon\in(0,8H)$, this particular $\theta$ is in $(0,1)$.
Now, if we choose

$N\geq\frac{8H^{4}(B_{p}+\rho^{p})^{2}}{\rho^{2p}\epsilon^{2}}\mathrm{log}\left(\frac{16H^{2}\left\lvert\mathcal{S}\right\rvert\left\lvert\mathcal{A}\right\rvert(HB_{p}+(H\vee\rho^{p}))}{\rho^{p}\delta\epsilon}\right),$

we get $\lVert V_{1}^{*}-V_{1}^{\widehat{\pi}}\rVert_{\infty}\leq\epsilon$
with probability at least $1-\delta$. ∎


# An Investigation of Indian Native Language Phonemic Influences on L2 English
Pronunciations

Shelly Jain1 Priyanshi Pal2
Anil Vuppala1 Prasanta Ghosh2 Chiranjeevi Yarra1
1Speech Lab, Language Technologies Research Center (LTRC), IIIT, Hyderabad,
500032, India
2Electrical Engineering, Indian Institute of Science (IISc), Bangalore,
560012, India
<EMAIL_ADDRESS>{priyanshipal<EMAIL_ADDRESS>
{anil.vuppala<EMAIL_ADDRESS>
###### Abstract

Speech systems are sensitive to accent variations. This is especially
challenging in the Indian context, with an abundance of languages but a dearth
of linguistic studies characterising pronunciation variations. The growing
number of L2 English speakers in India reinforces the need to study accents
and L1-L2 interactions. We investigate the accents of Indian English (IE)
speakers and report in detail our observations, both specific and common to
all regions. In particular, we observe the phonemic variations and
phonotactics occurring in the speakers’ native languages and apply this to
their English pronunciations. We demonstrate the influence of 18 Indian
languages on IE by comparing the native language pronunciations with IE
pronunciations obtained jointly from existing literature studies and
phonetically annotated speech of 80 speakers. Consequently, we are able to
validate the intuitions of Indian language influences on IE pronunciations by
justifying pronunciation rules from the perspective of Indian language
phonology. We obtain a comprehensive description in terms of universal and
region-specific characteristics of IE, which facilitates accent conversion and
adaptation of existing ASR and TTS systems to different Indian accents.

##  1 Introduction

India has approximately 1,652 languages and dialects from five language
families – Indo-Aryan, Dravidian, Austro-Asiatic, Tibeto-Burman and Tai-Kadai
Dryer and Haspelmath (2013). Besides languages native to India, English is a
lingua franca in education, law and administration Kim et al. (2011); Ng and
Hirose (2012), gaining importance as a second language. However, existing
speech systems are unable to handle the increasing English use, as people
impose their native languages (L1) behaviours on their spoken English (L2).
These influences result in extensive diversity in the spoken English. On the
other hand, Indian languages possess similar phonology due to shared region or
language family. The diversity of native languages influences English in each
region, with the collection of spoken English varieties within India being
referred to as Indian English (IE).

Many measures have been attempted to handle the IE diversity. Sen (2003); Baby
et al. (2021) proposed models to automatically extract pronunciation rules
mapping General American English to IE. Ganji et al. (2019); Yarra et al.
(2019); Huang et al. (2020); Jain et al. (2021) described IE data and provided
lexicons at different levels of phonetic variation. Kumar et al. (2007) used
voice conversion to generate IE speech and discovered that the pronunciation
model is vital for good performance. Existing linguistic studies describing IE
characteristics examined single varieties, failing to handle the variability.
A thorough investigation involving Indian native language phonology is
crucial. By observing L1 phonology, their influence on L2 English speech can
be determined. To address this, we investigate Indian native language
influence on English, using a diverse IE corpus Yarra et al. (2019); Pal et
al. (2022). By describing IE behaviour, one can handle unseen IE varieties,
either adapting existing systems to specific varieties or handling unusual
pronunciations due to L1 influence. This also assists in tasks like accent
recognition, mispronunciation detection and diagnosis (MDD), and native
language recognition. Consequently, this will enable the development of speech
applications designed for the diverse varieties of IE.

In this paper, we perform linguistic analysis on IE pronunciation by
considering the speakers’ native languages. We organise the behaviours of 18
Indian languages using phonemes and phonotactics, apply them to English, and
categorise the pronunciations as generalised ("universal") or regional. We use
Indian language characteristics to validate IE pronunciation rules compiled
jointly from data and prior linguistic studies. Hence, we derive linguistic
rules to empirically verify intuitions about Indian language influence on IE
speech from the perspective of both L1 and L2. Our results can help develop
speech systems robust to Indian variation. The universal characteristics are
useful for custom lexicons and tasks like Indian accented ASR and TTS;
regional characteristics provide detailed accent information for MDD and
accent conversion.

The paper is organised as follows. The preliminary work which forms the basis
for this study is detailed in Section 2. We describe our procedure and compile
our observations about native language characteristics in Section 3. In
Section 4, we discuss which Indian native language characteristics are
realised in Indian English and which characteristics are verified by the
study. Some applications are provided in Section 5. We conclude the paper in
Section 6. Finally, we address some limitations of our approach in Section 7.

##  2 Preliminary Study

###  2.1 Corpus

We consider Indic TIMIT, consisting of IE speech recordings of 80 speakers
from different demographic regions with a few Indian states – Northeast, East,
North, Central, West and South Yarra et al. (2019). Each region is composed of
a few Indian states. Since state boundaries were linguistically motivated,
geographical and linguistic boundaries are aligned India (1956). Hence, the
native languages of the speakers from each of the regions are among the
languages prominent in the respective region.

They were divided into the following five groups, with and equal number of
speakers:

  * •

Group 1: (Northeast and East) Maithili, Nepali, Oriya, Bengali, Assamese,
Dimasa, Mog, Manipuri

  * •

Group 2: (North and Central) Malwi, Marwari, Hindi, Punjabi

  * •

Group 3: (West) Gujarati, Marathi, Konkani

  * •

Group 4: (Upper South) Kannada, Telugu

  * •

Group 5: (Lower South) Malayalam, Tamil

Manipuri, Mog and Dimasa are Tibeto-Burman, Groups 4 and 5 are Dravidian, and
the rest Indo-Aryan. Also, the Austro-Asiatic family influences Bengali,
Assamese and Nepali, and the Indo-Aryan family influences Kannada and Telugu.
Assamese is further influenced by the Tibeto-Burman family.

Indic TIMIT also consists of phonetic transcriptions for 2,342 recordings,
annotated by two linguists. Pal et al. (2022) obtained annotations for 15,974
recordings, with over 190 recordings from native speakers (omitting Manipuri).
In these recordings, the managed to cover the entire TIMIT stimulus spoken by
native speakers from each region. Uniform influence from the region’s
languages was assumed. They reported good intra-rater agreement with Cohen’s
Kappa score Cohen (1960) of 0.827.

Rule No. | Category 1 | Category 2 | Category 3
---|---|---|---
RP | IE | RP | IE |  RP | IE
1 | /E/ | /e/ | /U/ | /u/ |  /n/ | /@ n/
2 | // | /@/ | /aU/ | /au/ |  */S/ | /s/
3 | /d/, /t/ | / d/, / t/ | /j U/ | /u/ |  */v/ | /b h/
4 | /T/ | /∥[t h/, /∥[t/ | // | /@ r/ |  */f/ | /p h/
5 | /D/ | /∥[d/ | /A/ | /a r/ |  /oU/ | /o:/
6 | /l/ | /@ l/ | /I d/ | /e d/ |  /eI/ | /e:/
7 | */z/ | /s/ | /S n/ | /@ n/ |  /6/ | /O:/
8 | */I/ | /i/ | /@ n/ | /e n/ |  /@U/, /E@/, /Ie/, /A:/, /O:/ | -
Table 1: IE pronunciation rules relative to RP. ‘*’ indicates native language
specific rules

###  2.2 Previous findings from the study

A few works characterised IE pronunciation relative to Received Pronunciation
(RP) Wells (1982); Bansal (1990); Bansal and Harrison (1994); Mesthrie (2008);
Sailaja (2012). Pal et al. (2022) analysed the variations of IE against RP by
validating pronunciation rules from literature against the rules obtained in a
data-driven manner from the phonetic transcriptions of 15,974 recordings, and
also reporting rules newly derived from the data. The comparison was done at
word level between canonical RP transcriptions and manually annotated IE
transcriptions.

A set of rules was obtained, indicating IE variations relative to RP. They
were segregated into three categories based on where they were observed, as
shown in Table 1. The phones marked in red were absent in the data and could
not be observed.

  * •

Category 1: This consists of all the phonetic rules mentioned in literature
which were also obtained from the data-driven approach that was considered Pal
et al. (2022).

  * •

Category 2: The rules in this category were obtained from the data-driven
approach based on the threshold criteria, but were absent in existing
literature.

  * •

Category 3: This category consists of rules which occurred only in the
literature, but were not obtained from the data-driven approach. The rules of
this category were not obtained for either of two reasons. The first reason
was the pronunciation rules produced by the data happened to be contradictory
to rules regarding the same phones that were obtained from literature study.
The second reason was that, while a set of rules in the literature described
the effects on phones, the phones in these rules were absent from the data and
hence could not be analysed.

Though Pal et al. (2022) considered a large number of phonetic transcriptions,
the rules of Category 2 were absent from literature. This has two possible
reasons: (1) existing literature failed to consider all IE varieties; or (2)
the new data-driven rules were incorrect. To analyse this, we study the
influences of Indian native languages (L1) on IE (L2) and validate the new
rules. We also analyse how these influences could result in the rules reported
in the existing literature as seen in Categories 1 and 3.

##  3 Observations

To analyse L1 influence on IE (L2), we study their properties. We profess that
observing sounds and their changes in L1 provides insights into the
pronunciation variations in L2. Hence, we study each Indian language
individually and in relation to other Indian languages which are
geographically or genealogically close. We study the L1 phonemes to understand
the fundamental variations and categorise the phonemes based on their presence
in Indian languages. The greater the number of languages having a phoneme, the
greater the salience of that phoneme in the accent of L2. We also study L1
phoneme interactions through phonotactics, which determine the valid phoneme
sequences. Speakers tend to enforce L1 phonotactics on L2 during speech, so by
observing these we can understand pronunciation variations in L2 due to L1.

Table 2 details the 18 native Indian languages forming the subject our
analysis, along with their corresponding groups, regions of origin, language
family, and number of unique phonemes.

No. | Group | Region | Language Family | Language | Phoneme Count
---|---|---|---|---|---
1 | Group 1 | East | Tibeto-Burman | Dimasa | 21
2 | East | Tibeto-Burman | Mog | 36
6 | East | Indo-Aryan | Maithili | 56
5 | East | Indo-Aryan | Oriya | 49
4 | East and Northeast | Indo-Aryan | Bengali | 47
3 | Northeast | Indo-Aryan | Assamese | 40
7 | Northeast | Indo-Aryan | Nepali | 46
8 | Group 2 | North | Indo-Aryan | Punjabi | 51
9 | North | Indo-Aryan | Marwari | 50
10 | North and Central | Indo-Aryan | Hindi | 55
11 | Central | Indo-Aryan | Malwi | 46
12 | Group 3 | West | Indo-Aryan | Gujarati | 47
13 | West | Indo-Aryan | Marathi | 48
14 | West | Indo-Aryan | Konkani | 55
15 | Group 4 | Upper South | Dravidian | Kannada | 50
16 | Upper South | Dravidian | Telugu | 55
17 | Group 5 | Lower South | Dravidian | Malayalam | 54
18 | Lower South | Dravidian | Tamil | 37
Table 2: Native Indian languages of the speakers

###  3.1 Universal characteristics

Most major Indian languages share phoneme inventories, including those in this
study Kishore et al. (2002). We call the shared properties universal
characteristics. Some examples seen are the replacement of alveolar stops
(/t/, /d/) with dental (/∥[t/, /∥[d/) and retroflex (/ t/, / d/) stops, and
the phonemic distinction of aspirated and unaspirated consonants. Indian
languages also possess a greater number of vowels, though there is not much
overlap with native English vowels. Additionally, Indian languages have
syllabic orthography with the inherent vowel schwa (/@/).

Figure 1 shows the frequency corresponding to the occurrence of phonemes in
the 18 Indian languages studied. The phonemes are arranged in orthographic
convention with vowels followed by consonants. The stops are arranged by place
(velar, palatal, retroflex, dental, bilabial) and manner (unvoiced-
unaspirated, unvoiced-aspirated, voiced-unaspirated, voiced-aspirated) of
articulation111The second row of stops contains postalveolar affricates, but
kept with the stops to keep consistent with the nasals.. In the figure, the
left side, Universal, refers to the common phonemes part of the phoneme
inventories of most Indian languages. The right side, Regional & Other,
includes region-specific and foreign language phonemes. Borrowed phonemes
(e.g. Perso-Arabic consonant /q/) and regional phonemes (e.g. Bengali vowel
/oi/) are kept with associated standard phonemes (/k/ and /ai/ respectively).

A total of 70 unique phonemes were observed in the given 18 languages. After
recording the number of languages each phoneme was present in, we applied a
percentile ranking to determine their degree of prevalence in Indian
languages. This indicates whether the phoneme is universal, frequent or rare,
by applying a uniform threshold on their frequencies. In this case, the top
one-third ($\geq$ 66.7 percentile) phonemes occurred in 16 or more languages
and the middle one-third ($\geq$ 33.3 percentile) phonemes occurred in 10 or
more languages, while the bottom one-third phonemes occurred in fewer than 10
languages. These categories are indicated in red, yellow and green
respectively. Of the 70 phonemes, 9 phonemes occurred in all 18 languages
observed, of which it was surprising to note that only 2 were vowels.

Figure 1: Frequency of phonemes in Indian languages (green: high, yellow:
moderate, red: low)

Despite many similarities, Indian languages have specific features deviating
from universal characteristics. These include tonality, phonemic stress, and
vowel harmony. The greatest reason for deviation is difference in phoneme
inventories – best observed in Mog and Dimasa, the two Tibeto-Burman
languages, with the English of their native speakers being distinct from that
of other Indian languages.

###  3.2 Regional characteristics

We consider L2 English speech by L1 Indian language speakers uniformly from
each region (Section 2.1). The languages of a region are expected to exhibit
linguistic similarities due to either geography or genealogy. They do not
generally deviate from the universal characteristics, but each region exhibits
some unique features. Further, the behaviour of a few languages differs from
the rest in the region. This could be due to genealogy and the external
influence of neighbouring languages.

####  3.2.1 Lower South

The prominent characteristics of these languages (Malayalam and Tamil) are
vowel length distinction, and the lack of phonemic aspiration Krishnamurti
(2003). While Malayalam orthography has both aspirated and unaspirated
consonants, actual pronunciation of the aspiration does not affect
communication and is understood from context. On the other hand, Tamil lacks
aspirated consonants entirely. Tamil also lacks voicing, unlike most Indian
languages; voiced consonants can be identified based on the phonotactics of
the language Schiffman and Harold (1999); Keane (2004). In addition, both
possess several consonants (mostly trills and flaps like /*̄t/, /*̄n/, /*̄r/,
/*̄l/), which are not observed in other Indian languages Hamann (2003).

####  3.2.2 Upper South

Like the languages of the Lower South, these (Telugu and Kannada) exhibit
vowel length distinction and lack phonemic aspiration Krishnamurti (2003).
Both are similar to Malayalam, since aspirated consonants exist in their
orthographies but are undifferentiated in speech. Word-initial vowels are also
sometimes preceded by semivowels. For example, front vowels /i/ and /e/ are
preceded by /j/, and back vowels /u/ and /o/ are preceded by /V/. Telugu,
exhibits vowel harmony with /u/ Wilkinson (1974), and also frequent voicing of
medial consonants similar to Tamil Bhaskararao and Ray (2017).

On comparing the Southern languages, it is clear that non-phonemic aspiration,
vowel length distinction and consonant voicing are properties characteristic
of Dravidian languages irrespective of region.

####  3.2.3 West

The Western languages, Konkani, Marathi and Gujarati, exhibit schwa deletion
in a limited form, occurring word-finally in all, but also word-medially in
Gujarati Masica (1993). Konkani exhibits vowel length distinction (Marathi
does so only in orthography), and is also the only language with a different
inherent vowel //. Other unique properties are schwa fronting in Gujarati
Mistry (1996), lack of vowel nasalisation in Marathi, and consonant
palatalisation in Konkani Jain and Cardona (2007).

####  3.2.4 North

Similar to Gujarati, these languages (Malwi, Marwari, Hindi and Punjabi)
possess both vowel nasalisation as well as word-medial and word-final schwa
deletion Masica (1993). Hindi is more similar to Gujarati than the other
Northern languages, as it exhibits schwa fronting Shapiro (2003). The
commonality between them, observed across regions, can be attributed to close
genealogical relation. Punjabi is distinct from the others due to tonality,
gemination of consonants, and a unique form of vowel contrast. Punjabi vowels
exist in three distinct groups (front, central, back), contrasted primarily by
quality (central or peripheral) and secondarily by vowel length Shackle
(2003).

####  3.2.5 East

Unlike the other regions, the Eastern languages have three segments. The
first, with Maithili and Nepali, most resembles the universal characteristics.
In addition their vowels and semivowels are interchangeable Khatiwada (2009);
Yadav (2011). The second segment, with Oriya, Bengali and Assamese, possesses
a different inherent vowel /O/ Masica (1993). Both the segments also exhibit
limited schwa deletion and vowel nasalisation. The third segment, with Mog and
Dimasa, differs considerably. The languages have reduced phoneme inventories
compared to other regional languages, with much fewer vowels and consonants
Moral (1997); Miri (2003). They also have different phonotactics with stricter
sound rules. Thus, their phonemes and behaviour are quite distinct from other
languages in the region. Due to geographical proximity to them, Assamese also
bears some of their characteristics, especially the different consonants and
vowel harmony Mahanta (2008, 2012).

Language | Characteristics
---|---
|  Unique |  Regional |  Universal
Tamil |  Lack of voiced consonants |  Vowel length distinction |  Inherent vowel schwa /@/
|  Voicing of intervocalic consonants |  Non-phonemic aspiration |
Malayalam |  |  Presence of trills and flaps |
Telugu |  Vowel harmony |  Vowel length distinction |
|  Voicing of intervocalic consonants |  Non-phonemic aspiration |
Kannada |  Semivowels preceding word-initial vowels |  |
Konkani |  Inherent vowel // |  Word-final schwa deletion |
|  Consonant palatalisation |  Vowel nasalisation |
|  Vowel length distinction |  |
Marathi |  No vowel nasalisation |  |
Gujarati |  Word-medial schwa deletion |  |
|  Schwa fronting |  |
Hindi |  Schwa fronting |  Schwa deletion |
Punjabi |  Tonality |  Vowel nasalisation |
|  Consonant gemination |  |
|  Vowel contrasted by quality instead of length |  |
Marwari |  |  |
Malwi |  |  |
Maithili |  Complex phonotactics |  Schwa deletion |
Nepali |  |  Vowel nasalisation |
|  |  Interchangeable vowels and semivowels |
Assamese |  Vowel harmony |  Schwa deletion |
Bengali |  No consonant clusters |  Vowel nasalisation |
Oriya |  |  Inherent vowel /O/ |
Mog |  |  Reduced phoneme set |
Dimasa |  |  |
Table 3: Universal, regional and unique characteristics of the 18 Indian
languages

A comparison of West, North and East indicates that Indo-Aryan characteristics
are schwa deletion and vowel nasalisation, with each branch showing unique
properties. In contrast to this diversity, the Tibeto-Burman languages are
characterised only by a reduced phoneme set. The influence of geographical
proximity is evident in the similarities between Konkani and the Dravidian
languages, and Assamese and the Tibeto-Burman languages.

All language characteristics have been compiled in Table 3. By observing the
sound characteristics of each region, it is easy to see that genealogy and
geography both considerably influence a language.

##  4 Discussion

We hypothesise that IE pronunciation variation (in Table 1) is due to L1
influence and exploit L1 behaviour to understand it. Since the pronunciation
rules are derived from data that is unevenly distributed among the speakers of
the 18 Indian languages, they are subject to statistical bias from languages
with more speakers. By linking recorded IE behaviour to the characteristics
observed in L1, we can attribute these characteristics to the number of
associated languages, instead of number of speakers, which is balanced only by
region. Consequently, we can determine whether these characteristics are
universal or region-specific. Thus, the rules verified against L1 phonotactics
will accurately describe the speakers’ behaviour.

###  4.1 Pronunciation rules which were verified by L1 and L2 characteristics

The first observation is consonant substitution. Indian languages lack
alveolar stops and dental fricatives, so speakers substitute these with
retroflex and dental stops, respectively. This is well accepted, corroborated
by both data-driven and literature study of IE (Category 1, Rules 3, 4, 5),
and examination of Indian languages (Section 3.1). Thus, these substitutions
are universal IE characteristics.

We also observe several regional characteristics. The prime example is
interchangeable voiced and unvoiced consonants, from the data analysis
(Category 1, Rule 7). Native language study allowed us to verify this as a
behaviour of Dravidian language speakers, especially for Tamil or Telugu
(Sections 3.2.1 and 3.2.2). This substitution is frequent due to a large
speaker fraction; however, since the number of languages causing this is
lower, the characteristic is not universal but regional to Upper and Lower
South. Lack of aspiration is another regional characteristic, which we again
observe in Dravidian language speakers – the speakers substitute the unvoiced
dental fricative /T/ with the unvoiced dental stop /∥[t/, while speakers of
most other Indian languages use the aspirated unvoiced dental stop /∥[t h/
(Category 1, Rule 4).

The main vowel substitutions were the replacement of diphthongs with
monophthongs. This is because, despite Indian languages having several
diphthongs, few are shared with RP. Thus, they are approximated using known
vowels. Prior literature predicted the resultant phones as long vowels, but
the rules derived from data showed the substitutions as short vowels (Category
3, Rules 5, 6, 7). This seems surprising, but observing the native languages
justifies the outcome. Of the 18 languages, only one-third distinguish vowel
length, making the observed short vowels and predicted long vowels equivalent.
Hence, for a universal characteristic, it is more important to correctly
identify the substituting vowel – usually, the diphthong’s first vowel.

The remaining vowel substitutions are as expected, where the vowel used has
the most shared properties. For example, most Indian speakers tend to use
tense vowels /e/, /@/, /i/ and /u/ in the place of corresponding lax vowels
/E/, /2/, /I/ and /U/. This is seen in the preliminary study, in Table 1
(Category 1, Rules 1, 2, 8; Category 2, Rules 1, 2). All vowel substitution
rules are universal as they are validated by the universal characteristics of
the native languages, regional behaviours being statistically insignificant.

###  4.2 Discarded pronunciation rules

Several predicted substitutions contradicted observed native language
behaviours and were discarded. The first is palatalisation, i.e. the insertion
of semivowel /j/ (Category 2, Rule 3). This is present in transcriptions but
only occurs to a minor degree in the English words. Being almost non-existent
in Indian languages, palatalisation is not distinguished from non-palatals. As
a result, native Indian language speakers only perceive the distinct
pronunciation of palatals. This direction requires future exploration for a
better conclusion, hence we discard the substitution in this study. Similarly,
the limited data and literature regarding gemination and the inconsistent
occurrence of schwa insertion (Category 1, Rule 6; Category 2, Rule 7;
Category 3, Rule 1) could not be validated from the perspective of L1-L2
interactions. Several rules were excluded due to lack of definite cause
(Category 2, Rules 4, 5, 6, 8).

Another kind of substitution discarded was the set of rules which could not be
verified by data analysis, despite being observed in descriptions of both IE
and native languages. In addition, we discarded certain behaviours predicted
by the L1 phonotactics which were not observed in the data-driven study. The
regional characteristics of Oriya, Bengali and Assamese (in Section 3.2.5),
suggested the undifferentiated use of /b/, /v/, /V/, and /w/ in English
(Category 3, Rule 3). Additionally, literature suggested that Telugu speakers
tend to substitute /S/ with /s/ (Category 3, Rule 2), and that Gujarati and
Marathi speakers tend to substitute /f/ with /p h/ (Category 3, Rule 4).
However, contrary to expectation, L2 pronunciations in the preliminary study
are consistent with those of other regions.

##  5 Applications

Modified lexicons are a popular method for dealing with non-native accents. A
pronunciation dictionary for Indian English was devised by Jain et al. (2021),
to convert CMU dictionary Weide (1998) codes to the Common Phone Set (CPS)
Ramani et al. (2013), a set of phonetic codes which is popular in Indian
multilingual speech systems. The dictionary substitutes the phones of General
American English with the phones from native Indian languages, relying on the
prominence of the substituted phones in Indian English to produce notable
results. However, such a simple measure fails to deal with the variety in
Indian English and is less effective when applied to specific regional
accents. To resolve this issue, it is essential to have a larger dictionary
with the sounds of all regional varieties.

In addressing this aspect, the analysis in our work is beneficial. Since we
provide descriptions of regional and general Indian English behaviours, it
becomes simple to apply this knowledge and thus account for any pronunciation
variations. The universal characteristics are useful for handling unseen
accents of Indian English, and regional characteristics are useful for either
adapting existing systems to specific Indian English varieties or handling
unusual pronunciations due to native language influence. By providing
characteristics for the different regional varieties, identifying and thus
correcting to and from desired varieties becomes possible. In addition to
accent adaptation, the Indian English profile can further assist in tasks like
accent recognition, mispronunciation detection and diagnosis, and native
language recognition by allowing the identification of region-specific
behaviours.

##  6 Conclusions

In this paper, we study the phonemic variations and phonotactics of 18 Indian
languages and analyse them against a data-driven study of IE pronunciations.
From this, we compile the linguistic characteristics which cause universal and
region-specific pronunciation variations in IE, validated from the perspective
of both L1 and L2. Hence, we empirically verify intuitions about native
language influence on Indian English. Our linguistic profile is valuable for
the development of speech systems robust to Indian context. The current
analysis was on the phonemic space, but future efforts could explore the
phonetic space by observing allophones in context. Another avenue is the
development of a phonotactic similarity index, which would allow for
qualitative assessment of phonemic processes in languages and their influence
on other languages.

##  7 Limitations

Certain conclusions drawn from the analysis are limited by the approach taken.
The discussions detailed in Section 4 rely upon the work done by Pal et al.
(2022) and make use of their final list of rules describing IE pronunciation
relative to RP. For this, we assume the data-driven study conducted by them,
which contains 4 to 5 speakers per native language, is a sample which is
representative of the full population of native speakers for each language.
Additionally, without observing the data from Indic TIMIT, we cannot comment
on the utterances themselves, or the effect of any possible phonological over-
correction from the speakers while recording the sentences.

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