In Ocotepec Mixe, the stem-initial sibilants /s tÉs ß/ undergo a palatalization process when the prefix /j/ is added. Descriptions of other Mixe languages report that this palatalization is realized either as addition of a glide (in the case of the alveolar and retroflex sibilants) or as a change in the primary place of articulation (in the case of the affricate). The acoustic measurements in the present study indicate that all palatalized sibilants in Ocotepec have an additional glide, unless they are followed by the high front vowel(s) /i (e)/, and that both the affricate and retroflex fricative show a consistent change in primary place of articulation under palatalization

Avelino, Heriberto

Hamann, Silke

English

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AN ACOUSTIC STUDY OF PLAIN AND PALATALIZED SIBILANTSIN OCOTEPEC MIXESilke Hamann & Heriberto AvelinoUtrecht University & UC Berkeley / Stanford Universitysilke.hamann@let.uu.nl & avelino@berkeley.eduABSTRACTIn Ocotepec Mixe, the stem-initial sibilants /s tÉs ß/undergo a palatalization process when the prefix /j/is added. Descriptions of other Mixe languagesreport that this palatalization is realized either asaddition of a glide (in the case of the alveolar andretroflex sibilants) or as a change in the primaryplace of articulation (in the case of the affricate).The acoustic measurements in the present studyindicate that all palatalized sibilants in Ocotepechave an additional glide, unless they are followedby the high front vowel(s) /i (e)/, and that both theaffricate and retroflex fricative show a consistentchange in primary place of articulation underpalatalization.Keywords: Mixe, acoustics, palatalization,sibilants, retroflex.1.  INTRODUCTIONSanta Maria Ocotepec is a Mixe-Zoquean languagespoken in Northeastern Oaxaca, in the district ofTotontepec Villa de Morelos. Like other Mixelanguages (cf. [5]), Ocotepec has a third personmarker /j/, which is prefixed to the stem of a word.This morpheme is usually realized as secondarypalatalization of the stem-initial consonant, see theexample in (1a).(1)  a)   [ka˘n]     ‘salt’      [kJa˘n]   ‘his/her salt’      b)   [tÉsim]    ‘gourd’       [tÉSim]    ‘his/her gourd’For the alveolar affricate /tÉs/, affixation of /j/triggers a change in the primary place ofarticulation towards the postalveolar [tÉS], asillustrated with the example in (1b).Besides /tÉs/, Ocotepec has two further sibilants,the native retroflex /ß/, and the Spanish loansibilant /s/, see the overview in Table 1.Table 1: Sibilants of Ocotepec Mixe.plain palatalizedtÉsstÉSsJßß JBoth also undergo palatalization when the prefix /j/is added. Mixe palatalized /s/ is usually describedas sequence of plain sibilant and short glide, i.e. asexhibiting secondary palatalization. For the post-alveolar fricative the descriptions differ. In IsthmusMixe, spoken in Eastern Oaxaca (in the vicinity ofGuichicovi), the corresponding segment is realizedas laminal postalveolar [S], which exhibitssecondary palatalization (see the phonetic study byDieterman [4]). In Totontepec Mixe, a closeneighbour of Ocotepec, however, the postalveolaris realized as [ß], and Crawford [3] describes it ashaving a “somewhat fronted and not retroflexedvariant” (p.42) when palatalized. This is in linewith Hamann’s [8] claim that retroflex consonantsare de-retroflexed when palatalized because of theopposing tongue gestures involved in retroflexionand palatalization.In the present study we compare the acousticcharacteristics of the plain and palatalized sibilantsin Ocotepec Mixe. In doing so, we determinewhether the place of articulation for the retroflexsibilant in Ocotepec changes under palatalization.In addition, we test whether only the alveolar andretroflex sibilants in Ocotepec are realized with anadditional glide when palatalized and the alveolarfricative is not, as described for Totontepec Mixe([3]) and Ishthmus Mixe ([4]).2.  ACOUSTIC ANALYSISWe recorded one male and two female adult nativespeakers of Mixe in the field. The recordings weremade on a portable analogue tape recorder andwere digitized at 22,050 Hz.For the sibilants /s/ and  /tÉs/ and  theirpalatalized counterparts we recorded six wordseach, and for the /ß/ and its palatalized counterpartfour words, all given in the Appendix. The wordswere produced in isolation and were repeated threetimes.Segmentation and labelling of the targetsibilants was done manually based on spectrogramand waveform. Acoustic measurements of thefollowing parameters were performed by usingPRAAT [1]. We measured the duration of the targetsibilants from beginning to end of the fricationnoise. Furthermore, we measured the duration of afollowing glide if present. The cessation of sibilantfriction noise was considered the starting point ofthe glide, and its endpoint was determined on thebasis of the intensity of the signal (an increase ofintensity for the following vowel) and the course ofthe first three formants.In addition, we measured centre of gravityvalues for the whole duration of the sibilant tokens,excluding the first and last 10 percent of eachtoken. The centre of gravity was calculated byweighting the frequencies in the spectrum by theirpower densities (see e.g. Forrest et al. [6]). Beforeapplying this measure, we filtered the signal toexclude the region below 900 Hz.3.  RESULTSIn the following analyses we included 285 tokens,144 contained a plain and 141 a palatalizedsibilant. We had 75 tokens with /ß/, 102 with /s/,and 107 with /tÉs/.3.1.  Duration of sibilantsA two-factor ANOVA (fricative and palatalization)pooled over the three speakers showed asignificant effect of both fricative andpalatalization on duration measurements (fricative:F(2, 283)=326.983, p<0.001; palatalization: F(1,284)=14.781, p<0.001). The retroflex sibilantshowed the longest and the sibilant part of thealveolar affricate the shortest duration. Though thepalatalized sibilants all show longer durations thantheir plain counterparts, cf. Figure 1, thedifferences within sibilant pairs are not significant.Figure 1: The mean duration values for the Ocotepecplain and palatalized sibilants.75.8122.7140.466.9149.7 133.2020406080100120140160123Duration (ms)plain palatalizedOur findings on the short affricate friction are inaccordance with earlier studies, where the frictionpart of an affricate was reported to be shorter thanthat of a fricative, see e.g. Castleman & Diehl [2]on American English.Consistent durational difference such as thosewe found between alveolar and retroflex fricativeshave not been reported in the literature. In Gordonet al.’s study [7], five of the six Tamil subjectsshowed a longer duration for the retroflex /ß/ thanfor the alveolar /s/, but one subject displays thereverse pattern.3.2.  Presence of glidesWe found that none of the 144 tokens with plainsibilants has a glide, in accordance with theexpectations. For the 141 tokens with palatalizedsibilants, 104 had a glide (72.2 %). The remaining37 palatalized tokens consisted of all tokens of /tÉSi/and /tÉSe/ (eighteen in total). Furthermore, alleighteen tokens of /sJi/ and one token of /ßJu/belonged to this group.We can conclude that the palatalized affricate inOcotepec is realized with a glide, unless followedby /i/ or /e/. This is in contrast to what has beendescribed for other Mixe languages ([3, 4]), wherethe palatalized affricate does not surface with aglide.In our data, an avoidance of derived /ji/ couldnot only be observed after /tÉS/, but also after /s/(/sje/, however, did occur). We cannot statewhether /ßJi/ and /ßJe/ are also avoided, because wedid not include any words with retroflex sibilantsfollowed by /i/ or /e/ in our experiment. Anavoidance of palatal glide plus high front vowel iscross-linguistically quite common and usuallyascribed to the acoustic and perceptual similaritybetween the two segments ([9]). A furtherexplanation might be the articulatory effortinvolved in the production of /ji/ sequences, wherethe glide has to be articulated with a higher andmore fronted tongue position than usually (seeLaver [10, p. 298] on English and the Chentudialect of Chinese).The glides following the palatalized sibilants donot differ significantly in their duration.3.3.  Centre of gravityThe centre of gravity (or: spectral mean) correlateswith the size of the front cavity, and is lower forpostalveolar articulations and higher for alveolarones. We therefore expected the Ocotepec retroflexsibilant to have lower spectral mean values thanany other sibilants in this language.Our measurements are given in Figure 2, wherewe present the data for the three subjectsseparately, due to large inter-speaker variation./s/           /ß/       /tÉs/Figure 2: Spectral mean values for the Ocotepec plainand palatalized sibilants, for speakers one, two (bothfemale), and three (male).Centre of gravity (kHz)2 3 4 5 6 7 8jssjtstCentre of gravity (kHz)2 3 4 5 6 7 8jssjtstCentre of gravity (kHz)2 3 4 5 6 7 8jssjtstThe plain retroflex tokens have indeed lowestvalues for all three speakers, as expected. Thespectral mean values for the palatalized retroflextokens, however, are higher than those for the plainretroflex ones (on average 0.85 kHz). They almosttotally overlap with the values for the palatalizedaffricate /tÉS/ (the latter are on average 0.14 kHzlower). This overlap is a clear indication that thephonologically palatalized retroflex is not realizedas retroflex but as laminal postalveolar or alveolo-palatal (the small average difference between  /tÉS/and /ßj/ might be interpreted as the realisations ofthe fricative parts as [S(j)] and [˛], respectively,compare the difference in centre of gravity valuesfor the same surface sounds in Polish measured byZygis & Hamann [11]).The values for the palatalized affricate tokensare lower and very distinct from the values for thefricative part of the plain affricate tokens. Thissupports the postalveolar status of the palatalizedaffricate, in accordance with the literature.Figure 3: Spectral mean values for the Ocotepecsibilants followed by the vowel /o/, for the same threespeakers as in Figure 2.Centre of gravity (kHz)2 3 4 5 6 7 8jssjtstCentre of gravity (kHz)2 3 4 5 6 7 8jssjtstCentre of gravity (kHz)2 3 4 5 6 7 8jssjtstThe tokens of alveolar /tÉs/, /s/ and /sj/ have highestcentre of gravity values. They overlap largely witheach other and are scattered over an area of 2 – 3.5kHz.In the present study, we did not control forvowel quality, and as a consequence, the sibilantsare followed by different sets of vowels. Only theback mid /o/ occurred after every sibilant. Toexclude a possible influence of the different vowelcontexts, we additionally looked at the spectralmean values for sibilants followed by /o/, only.These values, as presented in Figure 3, do not yieldany additional findings, but confirm the ranking ofsibilants in (2) that emerged from Figure 2 (where“<” stands for “has a lower spectral mean than”):(2)      /ß/   <   { /tÉS/, /ßj/ }   <   { /tÉs/, /s/, /sj/ }A disambiguation of categories with overlappingcentre of gravity values (in curly brackets) isprobably performed with additional parameterssuch as stop closure and formant transitions.Speaker oneSpeaker twoSpeaker twoSpeaker threeSpeaker oneSpeaker three4.  DISCUSSIONThe present study compared the acousticcharacteristics of plain and palatalized sibilants(two fricatives and one affricate) of Santa MariaOcotepec Mixe and checked whether these soundsare realized in the same way as correspondingsibilants in neighbouring Mixe languages.We found that in Ocotepec all three palatalizedsibilants are realized with a palatal glide, incontrast to reports on other Mixe languages, whereonly the two palatalized fricatives have a glide. Inour data, the glide did not surface with a following/i/ (for affricate and alveolar fricative) or /e/ (forthe affricate, only). Such restrictions on sequencesof palatal glide and front vowels were not reportedbefore in Mixe, but are quite common cross-linguistically.Furthermore, we found that both the affricateand the retroflex fricative show a change in placeof articulation when palatalized. The palatalizedaffricate is realized as postalveolar, as is commonfor Mixe languages. The so-called palatalizedretroflex sibilant was shown to have a similarcentre of gravity than the friction phase of thepalatalized affricate, indicating a laminal post-alveolar articulation. This observation is inaccordance with what has been reported for theneighbouring language Totontepec by Crawford[3], and with the general claim by Hamann [8] thatpalatalization and retroflexion are articulatorilyincompatible.On the basis of our findings, the sibilant systemof Ocotepec in Table 1 has to be revised as follows:Table 2: Sibilants of Ocotepec Mixe (revised).plain   palatalized non-occurringtÉsstÉSJsJtÉSJi, tÉSJesJiß SJ / ˛J (? SJi)The (non)existence of [SJi] sequences can only bedetermined on the basis of further recordings. Inaddition, future articulatory studies need to clarifythe exact realization of the sibilants in Ocotepec,specifically of the palatalized “retroflex” sibilant.5.  ACKNOWLEDGEMENTSWe would like to thank our subjects Federica Diaz,Engracia Perez, and Rodrigo Vazquez, as well asPaul Boersma for technical advice. This study wasmade possible by a UC Berkeley grant to HeribertoAvelino and a NWO grant to Silke Hamann.6.  APPENDIXIn the orthographic representations of the Ocotepecwords below we used the following transcriptionalconventions: ë = [´],  ch = [tS],  x = [ß],  y = [j], and' = [/]. Note that the words with initial /s/ are allloanwords from Spanish.serbesa – syerbesa ‘(his/her)  beer’seboya – syeboya ‘(his/her)  onion’sopa – syopa ‘(his/her)  soup’silantro – syilantro ‘(his/her)  coriander’siruela – syiruela ‘(his/her)  plum’sueter – syueter ‘(his/her)  sweater’tsokën – chokën ‘(his/her)  ant’tsoo' - choo'  ‘(his/her) sapote (fruit)’tseeb- cheeb ‘(his/her)  chicken’tsim- chim ‘(his/her)  gourd’tsaam- chyaam ‘(his/her)  banana’tsëkën – chyëkën ‘(his/her)  remains’xaaxt – xyaaxt  ‘(his/her) larynx’xuum – xyuum ‘(his/her)  net’xooxën – xyooxën ‘(his/her) wind instrument’xookx – xyookx ‘(his/her)  colibri’7.  REFERENCES[1]  Boersma, P, Weenink, D. 2006. Praat: doing phoneticsby computer (Version 4.5.08) [Computer program].Retrieved December 20, 2006, from http://www.praat.org/[2]  Castleman, W.E., Diehl, R.L. 1996. Acoustic correlatesof fricatives and affricates. J. Acoust. Soc. Am. 99, 2546.[3]  Crawford, J.C. 1963. Totontepec Mixe phonotagmemics.Dallas: SIL.[4]  Dieterman, J. I. 2002. Secondary palatalization inIsthmus Mixe: A phonetic and phonological account.Ph.D. dissertation, University of Texas, Arlington.[5]  Elson, B. F. 1992. Reconstructing Mixe-Zoque. In:Hwang, S., Merrifield, W. (eds.) Language in context:Essays for Robert Longacre. Dallas: SIL, 577-592.[6]  Forrest, K., Weismer, G., Milenkovic, P., Dougall, R. N.1988. Statistical analysis of word-initial voicelessobstruents: Preliminary data. J. Acoust. Soc. Am.  84,115–124.[7]  Gordon, M., Barthmaier, P., Sands, K. 2002. A cross-linguistic acoustic study of voiceless fricatives. Journalof the International Phonetic Association 32, 141-174.[8]  Hamann, S. 2003. The phonetics and phonology ofretroflexes. Utrecht: LOT Publications.[9]  Kawasaki, H. 1982. An Acoustical Basis for UniversalConstraints on Sound Sequences. Ph.D. dissertation,University of California, Berkeley.[10] Laver, J. 1994. Principles of Phonetics. Cambridge:Cambridge University Press.[11] Zygis, M., Hamann, S. 2003. Perceptual and acousticcues of Polish coronal fricatives. Proc. 15th ICPhSBarcelona, 395-398.

An acoustic study of plain and palatalized sibilants in Ocotepec Mixe

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