PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Comparative Acoustic-Phonetic Analysis of Retroflex Consonants ofSome Indian Languages
Shyam S. Agrawal1; Shweta Bansal2; Shweta Sinha3
12

KIIT College of Engineering,Gurugram, India
3

Amity University, Gurugram, India

ABSTRACT
Retroflexion is an important phonological category in many Indian languages. This paper puts forward aneffort made to present the findings of acoustic characteristics of retroflex sounds that significantly describe
and differentiate them from other sounds. The retroflex sounds /ʈ/, /ʈʰ/, /ɖ/, /ɖʱ/, /ɽ /, /ɽʱ/, /ɳ /, /ʂ/ areacoustically analysed for three Indian languages i.e. Hindi, Nepali and Punjabi. Selected words containing
each of these consonants in embedded in VCV positions were recorded by 50 native male and female
speakers of each of these three languages. Parameters such as spectral properties of burst, formant
transition(shifts), duration etc. were analysed. It has been observed that the formants F2, F3and F4 of the
burst and adjoining transitions, particularly the rising of F2 and falling of F3, F4 are significant. The minimal
differences between F2 and F3 values, strong release of burst, shorter duration of silence and VOTs arenoteworthy. The retroflex sounds /ɽ /and /ɽʱ/ which appear in medial and final positions of any word aremostly heard as rhetoric /r/. Some of the linguistic differences observed include /ɳ/ pronounced as /n/ and /ɽ/as /r/ in Nepali whereas /ɽʱ/ pronounced as /ɖʱ/ in Punjabi.
Keywords: Retroflex, Formant transition, Acoustic-Phonetic analysis

1. INTRODUCTION
Hindi is known for its large consonant inventory that features a four way contrast for voicing and aspiration.
This includes a full retroflex family of stops which contrasts with full dental stop series in addition to few
more retroflex consonants [1,2,7]. The origin of retroflex is found in Sanskrit and consecutively otherlanguages of Indo-Aryan family. Retroflex consonants are produced in a variety of forms depending upon the
shape of the tongue. The tongue may be either flat or concave or even with the tap curled back. The point ofcontact on the tongue may be with the tip (apical), with the blade (leminal) or with the underside of the tongue(subapical) (refer Figure1).
Hindi, Punjabi and Nepali belong to same language family i.e. Indo-Aryan. Punjabi language isspoken dominantly in the northern region of India, parts of Pakistan and also in few major countries like
Canada. The stop consonant system of Punjabi is similar to that of Hindi and other Indo-Aryan languages, but
the voiced aspirated series has been replaced by tones [9,17]. Nepali is primarily spoken in Nepal and in someregions of India and Bhutan. It has 20 obstruent’s. Pokharel (2) claimed that the production of Nepaleseretroflex stops is ‘apico-alveolar’, that is there is no curling backward movement of the tongue and thesegment is articulated directly at the alveolar ridge, rather than further back in the vocal tract. This is in1

ss_agrawal@hotmail.com
bansalshwe@gmail.com
3
ssinha@ggn.amity.edu
26836

contrast to the most of Indo-Aryan retroflex stops. Hindi retroflex consonants are generally apical post
alveolar, with a somewhat concave tongue.

Figure1. Articulation of retroflex consonants (1)The main objective of the present study is to provide detail analysis of features of retroflex sounds andin this context measure the similarity and dissimilarity between three languages i.e. Hindi, Punjabi and
Nepali. The paper is organized as: section 2 presents the methodology used for corpus design and analysis.
The statistics of parameters and the results of analysis are presented in section 3. The conclusion of the work
is presented in section 4.

2. METHODOLOGY
2.1 Design of Corpus
Table 1 outlines the retroflex sounds of Hindi, Punjabi and Nepali used in this study. The sounds/t/, /th/, /d/and /dh/ are common to all the three languages. The sounds /r/ and /rh/ are special sounds that occur in Hindi
only. The sounds /ɳ/, /ɽ/, /ɽʱ/ does not appear in the initial position of any word in Hindi and Punjabi. The
unvoiced fricative /ʂ/ is pronounced clearly in Hindi and not in other two languages. We have however, asked
the speakers of Punjabi and Nepali also to utter these sounds in the VCV contexts and compared theircharacteristics with those of Hindi sounds.
Table 1 – Retroflex of Hindi, Punjabi & Nepali

Manner of Articulation
Unvoiced unaspirated plosive
Unvoiced aspirated plosive
Voiced unaspirated plosive
Voiced aspirated plosive
Voiced unaspirated nasal
Unvoiced aspirated fricative
Flap voiced unaspirated
Flap voiced aspirated

Hindi (L1) Punjabi (L2) Nepali (L3)/ʈ / ਟ
/ʈ / ट
/ʈ / ट
/ʈʰ / ठ /ʈʰ / ਠ/ʈʰ / ठ/ɖ / ड /ɖ / ਡ/ɖ / ड
ढ
ਢ
/ɖʱ /
/ʈ /
/ɖʱ / ढण/ɳ //ɳ / ਣ
ष
/ʂ /
ड़
ੜ
/ɽ /
/ɽ /
ढ़
/ɽʱ/

Guided by the aim of the study all retroflex consonants were embedded in the vowel-consonant-vowel
context using three cardinal vowels /a/, /i/, /u/. The corpus was recorded by 50 native speakers of thelanguages under study. All the utterances were recorded on a portable sound recorder H4N and sampled at 16bit, 44.1KHz sampling rate.

6837

2.2 Acoustic Analysis:
The recorded samples were analysed using PRAAT and WAVESURFER Software. The desired
words were first segmented and stored in separate files. The acoustic analysis consists of extracting formant
frequencies at different positions along with durational measures in different vowel context. The value offormants have been measured at four different positions i.e. in steady state and terminating point of thepreceding vowel, the beginning (during the burst of plosives) and the steady state of the following vowels,
shown in figure 2.

Figure 2- Measuring points of retroflexion characteristics (word aʈʰa)Pronounced by a male speakerFor durational measures the duration of gap, VOT duration, VOT along with aspiration and VOT with voiced
aspiration have been measured for each retroflex sound.

3. Frequency Measurements and Results
For detailed analysis of acoustic parameters, the utterances were analysed using PRAAT and
WAVESURFER software tools. Fig 3 shows spectrogram of the four stop retroflex consonant in VCVcontext. To obtain the steady state and formant values at the terminating points in the consonants, the formant
measures are obtained for all the speakers in context of three vowels /a/, /i/, /u/. With the values obtained atfour different positions the differences between F1, F2 i.e. (F2-F1), between F2 and F3 i.e. (F3-F2) andbetween F3 and F4 i.e.(F4-F3) is computed. These values are averaged over individual vowels. Table 2
presents these values and the standard deviation at different position for three languages.

6838

Figure 3- Spectrogram of stop consonants
The transition of formants in the preceding and following vowels are quite significant clues in the
distinction of retroflex consonants, which distinguishes them from other categories of consonant sounds.
It can be observed that the transition between F2-F3 and F3-F4 is the largest for Nepali followed byHindi language, and is the smallest for Punjabi. It may be presumed that the degree of retroflexion in
Punjabi is higher than Hindi and among the three Nepali has the least retroflexion. In particular, therising of F2 and lowering of F3 and F4 in case of central and back vowels is evident from thespectrogram (refer Figure 3). In case of preceding vowel /a/ context, the formant F2 and F3 tend tomerge with each other. This phenomenon is consistent in all the three languages.
Table 2- Formant transition measurement of retroflex (stop consonants) in three languages
PositioTransitio

n

n

P_SS

F2-F1

F3-F2

F4-F3

Language

/aa/

SD

/i/

SD

/u/

SD

L1

400.98

14.50

1982.9832.35

430.2837.43

L2469.6017.25

2371.8162.49

336.74112.06L3

595.51

60.93

1910.35

67.11

524.2428.27

L11353.1946.85

315.28109.231863.75

122.73L21452.5030.55

454.11

40.07

1805.12374.38L31505.36150.27607.17445.21

1789.6332.74

L1

913.7641.89

1235.64235.551140.40132.17L21378.2975.27

773.6235.59

1121.01

266.24

6839

P_V

F2-F1

F3-F2

F4-F3

F_V

F2-F1

F3-F2

F4-F3

F_SS

F2-F1

F3-F2

F4-F3

L3

573.89104.481684.87403.8

1706.21211.65L1

987.9282.84

1890.6473.87

685.7824.92

L21273.5984.86

2045.00

45.10

745.2457.46

L3910.62140.401587.21237.92720.6647.18

L1640.88352.71397.1130.45

1182.4943.41

L2

277.61139.84421.96110.671088.39206.33L3643.45308.20467.72243.691490.44163.97

L1

999.30318.14789.81231.05940.7764.66

L21347.4288.63

363.01

71.46

940.3289.24

L31412.66

379.201582.13148.331260.32

113.70L1

851.33184.101804.6286.76

985.25268.62L2926.31377.462278.58111.91

669.49162.90L3815.78123.292094.64145.16746.88302.07L11025.74

124.82515.9870.27

1174.86270.69L21135.18

187.56483.5344.98

1420.82594.54L3732.72387.98468.9888.63

1273.8862.71

L1

1091.07184.43

978.20128.771105.3191.42

L21327.02271.25877.4937.39

1078.74

136.33L31275.93168.21880.84194.061260.16217.50L1

552.66

41.76

1896.2285.29

513.7738.38

L2

528.3644.95

2392.1931.52

492.4916.31

L3

597.51

58.01

1911.4220.59

675.5641.71

L11164.05110.57499.5930.14

1673.43

128.43L21180.01

143.48389.0049.99

1739.42593.37L31499.09125.15921.68177.091451.1251.49

L11126.8077.79

1025.15145.341240.61120.96L21474.01

148.46823.7125.89

898.40361.13L31014.1976.01

1554.07118.572086.29483.14

P_SS = Steady state of previous vowel, P_V = Termination of the previous vowel,
F_V = Initial values at the following vowel, F_SS = Steady state values at the following vowel.
It can be further observed that the changes in formants and formant transitions of the retroflex
consonants (belonging to same place of articulation) are only slightly affected by the changes in the mannerof production of these consonants i.e. due to aspiration or voicing or voiced aspirations.
Fig. 4 shows the spectrogram of other retroflex consonants which appear in Hindi but not in Nepali. The
sounds / ɳ/ and / ɽ / appear in Punjabi also. We asked the speakers of all the languages to pronounce all these
consonants. Measurements of formant frequencies at all the four positions (Fig. 2) were done for all theutterances. The major finding show that for Hindi speakers their characteristics match with the retroflex

6840

category quite well and in Punjabi the characteristics of / ɳ/ and / ɽ / matches also. However the sound /ɽʱ/becomes closer to / ɽ / and /ʂ/ becomes closer to /s/. Similarly in Nepali the sounds does not show theirretroflex character and they become closer to other categories of sound e.g. / ɳ/ closer to /n/, /ʂ/ closer to /s/, /ɽ / and /ɽʱ/ closer to /ɖ/.

Figure 4- Spectrogram of other retroflex consonants

4. Durational Measures and Results
In addition to frequency parameters several durational measures are obtained by averaging the values
over the three vowels separately. The average total duration of gap and VOT/Aspiration for all consonants issame in different vowel contexts, presented below in Table 3.
Table 3- Average Total duration of stop consonants

The detailed analysis of the durational measures under different conditions is outlined in Table 4. The
analysis of retroflex duration highlights the dissimilarity among the languages.

6841

Table4-Retroflex duration in three different languages
Durational

Hindi (L1)

Punjabi (L2)

Nepali (L3)

MeasuresGapड (ɖ)> ट (ʈ)> ठ (ʈʰ)>ढ (ɖʱ)

VOT/VOT+ढ (ɖʱ)>ठ (ʈʰ)>ट (ʈ)>ड (ɖ)

Aspiration
Total Durationढ (ɖʱ) >ठ (ʈʰ) >ट (ʈ) >ड (ɖ)ਟ(ʈ)> ਠ (ʈʰ)>ਢ (ʈ)> ਡ (ɖ)ਢ(ʈ)>ਠ(ʈʰ)>ਟ(ʈ)>ਡ(ɖ)ਢ(ʈ) >ਠ(ʈʰ) >ਟ(ʈ) >ਡ(ɖ)ट (ʈ)>ड (ɖ)>ढ (ɖʱ)> ठ (ʈʰ)
ढ (ɖʱ) >ठ (ʈʰ) >ट (ʈ) >ड (ɖ)ढ (ɖʱ) >ठ (ʈʰ) >ट (ʈ) >ड (ɖ)

The total duration of retroflex consonants in VCV context shows that it is higher for Nepali followedby Punjabi and Hindi. It shows Nepali speakers take more time in articulating these consonants compared tothe speakers of other two languages. However, duration follows the same order in all the languages i.e. ढ (ɖʱ)>ठ (ʈʰ) >ट (ʈ) >ड (ɖ). It is obvious that the duration of aspiration is much higher than the duration of VOT in
unaspirated consonants. For other retroflex consonants studied the analysis outline the following relation indifferent languages: in Hindi, ष(/ʂ/) > ढ़(/ɽʱ/) > ण(/ɳ /) > ड़(/ɽ /), for Punjabi, ष(/ʂ/) > ढ़(/ɽʱ/) > ण(/ɳ /) > ड़(/ɽ /) andfor Nepali, ष(/ʂ/) > ढ़(/ɽʱ/) > ण(/ɳ /) > ड़(/ɽ /) .
The duration of fricative retroflex sound which is unvoiced sibilant having apical post alveolar
articulation is higher than the other sounds. In Punjabi, the sound ष(/ʂ/) and ढ़(/ɽʱ/) does not occur as retroflex
sounds; ष(/ʂ/) becomes स(/s/) and ढ़(/ɽʱ/ ) is generally replaced by ड़(/ɽ /). Hence their properties do not matchwith retroflex consonants. Similarly in Nepali, these sounds are not pronounced as retroflex sounds but ष(/ʂ/)
as स(/s/) and ढ़(/ɽʱ/) as ड़(/ɽ /) somewhat closer to ड (/ɖ/) and ड़(/ɽ /).

5. Conclusions
The Articulation of the retroflex sounds is very clearly reflected in their acoustic characteristics and theco-articulation effects in proceeding and following vowels. These Characteristics can be distinguished fromthe other categories of sounds such as dental etc. In particular the position of the burst frequencies, transitionof the formants of the previous and following vowels particularly of second, third and fourth formants show
very specific transition associated with retroflex consonants. In particular F2 rising and F3 and F4 falling inall cases for all the languages.
These observations are in agreement with the results reported earlier by references [14,15] for Hindi and [47]for Nepali and [17] for Punjabi. There are some differences among Hindi, Punjabi and Nepali. While all thethree languages have all the four retroflex stops, our results have shown that the other retroflex sounds whichappear in Hindi but not in other languages show their characteristics as non-retroflex consonants. For
example the nasal retroflex /ɳ / appears to be closer to /n/ and (/ʂ/ closer to /S/, /ɽ / and /ɽʱ/ closer to /ɖ/ in
Nepali. Similarly /ʂ/ appears to be pronounced as /s/ in Punjabi, which indicates that Nepali speakers
articulate these sounds slower than the other two languages.

6842

6. Acknowledgements
The authors wish to acknowledge Dr. Harsh Vardhan, Dr. Neelima Kamrah, for their encouragement
and support in this work. They wish to thank Shambhu Sharan, Bidesh Das and A K Dhamija inconducting the experiments and analyzing the data. They also acknowledge partial financial supportof Deity, Govt. of India.
REFERENCES
1. https://en.wikipedia.org/wiki/Retroflex_consonant
2. Pokharel, M.P. (1989), Experimental phonetics of Nepali, PhD Dissertation, University ofPune, India. USA: Wiley; 2006. p. 887-909.
3. Ohala, Manjari (1999) “Hindi” in International Phonetic Association (Ed.) Hand Book ofInternational Phonetic Association: A guide to the use of IPA, Cambridge University Press, PP
100-103, ISBN 978-0-521-63751.
4. Kachru, Yamuna (2006), “Hindi” John Benjamins Publishing ISBN 90-272-3812-X
5. Phonetic Inventory of Punjabi Nayyara Karamat Center for Research in Urdu Language
Processing.
6. Khatiwada, Rajesh (2009), Jour IPA, 39 (3) 337-380, doi: 10.1017/50025100309940181.
7. Ladofoged, Peter, Maddisoon, Ian, (1996), the sounds of worlds languages, oxford, Blackwell,ISBN 0-631-19814-8.
8. John Esling (2010), Phonetic Notation, In Hardcastle, Laver & Gibbon Eds, the Hand book of
Phonetic Sciences, P. 693.
9. Ohala Manjari (1993), Aspects of Hindi Phonology, New Delhi, India, Motilal Banarsidas.
10. Arun,V.B.(1961) A Comparative Phonology of Hindi and Punjabi, Punjabi Sahitya
Academy,Ludhiana, pp1-182.
11. Harman, S (2003), The Phonetics and Phonology of Retroflexes (LOT, Utrecht) pp1-228.
12. Ladefoged, P and Bhaskara Rao , P (1983)” Nonquantal aspects of consonant production:
A study of retroflex consonants, J Phon, (pp 291-302
13. Ohala M and Ohala , J>J> (1982) “Phonetic Universals and Hindi Segment duration” in Proc.
Int.Conference on Spoken Language Processing, Ed. J Ohala at al, Edmonton, pp 831-834.
14. C. Smith at al (2013) “On distinguishing articulatory configurations and articulatory tasks:
15. Tamil retroflex consonants, J Acoust. Soc. Am. 133, 3609.
16. Verma Rajesh and Chawla Puneet “Comparative analysis of Hindi Retroflex and Dental CV
Syllables and their synthesis” Workshop on Spoken Language Processing, Mumbai, Jan
9-11,2003.
17. Agrawal S S and Stevens K N (1992) “Towards Synthesis of Hindi Consonants using KLSYN
88,Proc. ICSLP-92 pp 177-180.
18. Bhat, DNS (1973) Retroflexion and Retration, Jour. of Phonetics 2,pp 233-237.
19. Hussain Quandeel et,.al , (2017) , Acoustic characteristics of Punjabi Retroflex and Dental Stops,J.
Acoustic Soc, Am.141(6), pp 4522-4542.

6843