Vowel duration in Afrikaans: The influence of postvocalic consonant voicing and syllable structure Daan Wissing DepartmentofLinguistics, Potchej•troomUniversity for C. H. E., PrivateBagX6001, 2520 Potchej•troom, Republicof SouthAfrica
(Received19October1990;acceptedfor publication1 April 1992)
A productionstudywasconductedto investigatethe effectof vowellengtheningbeforevoiced obstruents,and the possibleinfluencethat the openness versusclosedness of syllableshaveon the temporalstructureof vowelsin somelanguages.The resultsrevealedthat vowelswere significantlylongerwhenfollowedby voicedconsonants than voiceless consonants. Vowel duration did not, however,vary with syllablestructure.However, vowelsin opensyllables followedby [ + voiced] consonantstendedto be longerthan when the followingconsonants were [ -- voiced].Theseresultsare discussed in the contextof currentknowledgeof other languages. PACS numbers:43.70.Fq, 43.70.Kv
INTRODUCTION
whentheseconsonants occurred in word-finalandprepausal
In this study, we focus on the duration of Afrikaans vowels in two contexts, voiced versus voicelessconsonants,
and open versusclosedsyllables.The lengthening-beforevoicingeffect,which is sometimesreferredto as shortening before voiceless consonants (Klatt,
1976), has been ob-
servedfrequently,especiallyin English.Word- and syllableboundary effecton vowel duration have been observedin a numberof languages,includingEnglishand Italian.
The phenomenonof lengthening-before-voicing was first identifiedby Houseand Fairbanks(1953) for English, and sincethen, numerousinvestigatorshave corroborated theseresults.Vowels tend to be longer when followed by voiced obstruentsthan when followed by voicelessconsonants.O'Shaughnessy ( 1981), for example,reportsthe same effectfor French, Fintort (1962) for Norwegian,Balasubramanian (1981) for Tamil, Van Dommelen (1982) for Dutch and German, and Slis and Cohen (1969) also for Dutch. Chen (1970) refers to similar results for Russian,
Korean,French, Spanish,Norwegian,and English.Klatt (1976), amongothers,claimsthisto be a universaltendency,but Mitleb (1984) arguesthat thisis not the casein Arabic. The results obtained by Crystal and House (1982)
stronglysupportthe lengthening-before-voicing effectfor longvowelsprecedingstops,but neithershortnor longvowels were lengthenedwhen followed by voiced fricatives. Crystaland House (1988a) point out that theseresultsare rather uncertain,sinceall occurrences weretallied, irrespective of word boundariesor pauses.They thereforereanalyzedthe durationsof the entiresetof longandshortvowels when followedby voicedand voicelessconsonants in word finalpositionirrespective of the post-consonantal condition, whenthe consonants wereword-finalbut not prepausal,and 589
J. Acoust.Soc. Am. 92 (1), July 1992
position(Crystal and House, 1988a). They concludedthat the lengthening-before-voicing effectis only applicableto vowelsprecedingprepausalword-finalconsonants. In the caseof Germanand Dutch, a languageclosely relatedto Afrikaans,studiesonthelengthening-before-voicing effecthave been confinedto the influencethat consonantsin intervocalic positionhaveonpreceding vowels(Van Dommelen, 1982). According to Van Dommelen the lengtheningeffectof the German intervocaliclenis (lax or voiced)stopconsonants on precedingvowelsis about65 ms (roughly40% ), andin the caseof Dutch, onlyabout19%. Slisand Cohen(1969) reporta meandifferenceof 30 msfor Dutch vowels in similar conditions.
The above-mentioned information of Van Dommelen
(1982) on Dutch andGermanalsopertainsto theeffectthat syllablestructuremight haveon the durationof vowels.Al-
thoughVan Dommelendoesnot usethe term open (or closed) syllable,his investigationexaminedvowelsoccurring in opensyllablessuchasin wordslike "hie-den" versus "hie-ten,"i.e., syllablestructure"C¾$CVC" ($ = syllable boundary). As a matterof fact,fewstudiesexplicitlyreferto syllable structurein thesense of openness andclosedness, exceptthe studiesof Farnetani and Kori (1986), and Rietveld and Frauenfelder (1987), who all statedthat vowelsare longer in open syllables (i.e., in "XV$CY" structures;X and Y = empty or representingone or more segment)than in closedsyllables("XVCSY"). In the caseof Italian, this differenceamountsto an averageof 31% (Farnetani and Kori, 1986). Contrary to these findings, Crystal and House (1990) report a tendencyfor stressedvowelsto be shorterin word-finalposition,i.e., opensyllables,than when followed by consonants.However, their data for stressedvowels in
0001-4966/92/070589-04500.80
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nonprepausal wordsindicatethat vowelsin opensyllables words,4 of the 16 wordsconsistof three syllableseach, the other12arebisyllabic.Thisseemsto beanunbalanced situaare about8% longerthan vowelsin closedsyllables(avertion as well, and could possibly have had an effect on the agesandpercentages deducedfromTable 1, p. 102), which is consistent with the results of Farnetani and Kori (1986) and Rietveld and Frauenfelder (1987). Balasubramanian (1981) found that Tamil vowels in closed syllableswere
longerwhen followedby voiceless consonants than when followedby voicedconsonants, while the oppositeoccurred in the caseof opensyllables.In thecaseof Tamil, the factors of lengthening-before-voicing and syllablestructureappear to be in close interaction with each other.
In the caseof Afrikaans, the followinghypotheseswere
outcome of the investigation.However, as Nooteboom
(1972) pointsout,whenthenumberof syllables thatremain to be producedin the wordswerekeptconstant,aswasthe casein thepresentexperiment, thiseffectiseliminated.Other factorsthat may have an effecton vowel duration are accentuation (Eefting,1991), prepausal lengthening ( Klatt, 1976), and non-word-finalshortening(Oller, 1973). In the presentexperiment, thesefactorswereheldconstant asfaras possible.
formulated:
( 1) Afrikaans vowels,when followedby voicedconson-
B. Subjects, testing and measuring procedures
ants,will belongerthanwhenfollowedby voiceless conson-
Four nativespeakersof Afrikaans,two of eachsex,participatedon a voluntarybasisand were not paid for their (2) Afrikaans vowelsin open syllableswill be longer services. The taperecordingsweremadein a professionally than vowelsin closedsyllables. equippedstudio.Each subjectread the list of 16 stimulus words,ten randomizedtimesat a normalspeakingrate. The stimuluswords containingthe regressiveassimilationrule I. METHOD wereclearlyindicatedfor the subjects'pronunciation.Those A. Stimulus material formsthat had not beenassimilatedproperlywererepeated. Sixteenstimuli were used,includinglong versusshort Of the 640 stimuli (4 subjectsX 10 readingsX 16 stimulus vowels,open versusclosedsyllables,and voicedversus words) only nineproductionswererejectedduringthe meavoicelessconsonants.Fricatives were equally distributed. surementphase. The vowel[a:] andthediphthong[o9i]represented thelong vowels(seeNooteboom,1972,for thegroupingof longvowC. Measuring procedures and criteria elsanddiphthongs intooneclass),and [a] and [e] repreTherecordedspeech tokensweredigitizedat a sampling sentedthe shortones.The consonantsfollowingthe vowels rate of 16 kHz and waveformsdisplayedon a computerterwere the voicelessfricatives, [f] and [s], and their voiced minal.Segmentation wascarriedout,anddurationsof vowcognates[v] and [z]. In the caseof syllablesclosedby elswereestablished usinga segmentation programwith auvoicedfricatives,thevoicingresultedfromtheapplicationof ditoryfeedback.The vowelonsetcoincidedwith the endof anoptionalphonological ruleof regressive assimilation of a thepreceding stopsor fricatives. The endof theunaspirated followingvoicedstop[d], whichoccurredat thebeginning stop( [k] in eachcase)wasmarkedafterthereleaseburst, ofthenextsyllable.Thiswasnecessary in viewof theabsence and that of the voicelessfricative ( [ s] or [ f] ) at the end of of voicedobstruentsin syllable-or word-finalpositionin nonperiodic noise.The offsetof vowelscorresponded with Afrikaans,like in manyGermaniclanguages, dueto a pho- thebeginning of thefricatives. In thecaseof thevoiceless [f] nological ruleof devoicing in thatposition(Trommelenand and [s] thiswaseasilydetectedat the pointwherea decrease Zonneveld, 1979;Wissing,1982). in amplitudeappearedcoinciding with thebeginning of nonThusthe completesetof stimuluswordswerethe fol- periodicnoise.Theendof vowelspreceding thevoicedfricalowing (the relevant phoneticinformationappearsin tives [z ] and [ v ] weretakento be the pointat which there
ants.
squared brackets;[a] and [e] = shortvowels;[a:] = long vowel,[o9i ] = diphthong consisting ofschwad- [i ]; $ = syllable boundary):
"õesk[a:$v]e"("chafed"), "besk[a:v$]de"("civilized"), "gesk[a:$f]ie" ("moderate chafing"), "besk[a:f$]te"
wasa suddendrop in amplitudeand high frequencyenergy in the waveform (Fig. 1).
II. RESULTS
("civilized", variant of "besk[a:v$] de"); "v [o9i$v ] e", ("fives"), "v [o9i$v ] de", ("fifth"), "v [ o9i$f]ie" ("little five"), v[o9iSf]tig"("fifty"); "s[eSz]e" (substandard form of"s [eS] se"sixes"),"s[ez$] de" ( "sixth"), "s[eS] si" ( "little six"), "s[ess] tig" ("sixty); "k [aSz] e" (substandard form of"k [ ass] e "boxes"), "k [ass] tig" ("make-believe"), "k [az$] dig" ("box-tight"), "k [ass] i" ("little box").
arrangedby syllabletypefor eachsubject.In general,the effectsof syllablestructureand consonantvoicingappear relativelyconsistentacrosssubjects.
The long vowelsare followedby either voiceless[f] or voiced[ v ], and the shortvowelsby either [ s] or [ z ]. These
As shown in Table II, the differencesbetween vowel durationswhenfollowedby voicedversusvoiceless conson-
unbalancedconsonantalcontextsacrosslongand shortvow-
ants were significant.For vowelspooledacrosssyllable
els werenecessary becauseof the unavailabilityof suitable setsof existingwordsin whichthepresenthypotheses could be tested. As to the number of syllablesin the stimulus
structure the difference was 36 ms (20%)
590
J. Acoust.Soc.Am.,Vol.92, No.1, July1992
The mean durations of the vowels are shown in Table I,
A. Consonant voicing
[F(1,56)
= 28.05,p = 0.0001]. In opensyllables only,thedifference was 42 ms (22%) [F(1,28) = 25.41,p = 0.0001], and in DaanWissing: Lettersto theEditor
590
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TABLE II. Interaction of vowel duration (in ms) as a function of conso-
[.8
nantvoicingandsyllablestructurefor all vowelsacrosssubjects(N = 631).
Consonantvoicing
li
•
!
-1. Zoo•e• dis•la• 0.1087S
Bcr: 0.1371S
Cr: 0. Z636S
d i for:
0.1265S
21 Ecr: 0. Z639S
E: 0. 3387S
Syllablestructure Open Closed
X
q- Voiced
184
174
179
-- Voiced
142
144
143
X
163
159
3
closed syllables only, the difference was 30 ms (17%) [F(1,28) = 7.82,p -- 0.0092].
minimal pairs are used.On the other hand, it might be absent,or largelyabsent,whenconnectedspeechmaterialsare used.A numberof investigations includingthe presentstudy are of the former type (House and Fairbanks, 1953;Fintoft, 1962; Van Dommelen, 1982; Balasubramanian, 1981), while the experimentsof Crystal and House ( 1982, 1988a, 1988b, 1990) are of the latter type. Accordingto the presentresults,the overall difference
B. Syllable structure
between vowel duration in the context of voiced versus voiceless consonants is about 20% for Afrikaans. This is
FIG. 1. Oscillogramof a portion of the word "s[ez]de." The vowel/e/ occursbetweenthe two verticaldottedand partiallydottedlines(indicated as 1 and 2). The first part of the voicedfricative/z/ liesbetween2 and 3.
As illustrated in Table II, the differencebetween vowel
duration in openand closedsyllablescollapsedacrossvoicing (4 ms, or 2%) was not significant [F(1,56)=0.38, p=0.5383]. Moreover, syllable structure (open versus closedsyllable) was not significantfor either voicedconsonant environment[F(1,28) = 0.99, p = 0.3286] ) or voicelessconsonantenvironment [F(1,28) -- 0.04, p -- 0.8516]. III. DISCUSSION
AND CONCLUSION
The resultsof this experimentdemonstrateadequately that the lenghtening-before-voicing effectis presentin Afrikaans,thussubscribing to the claimof the universalityof this phenomenon.With regardto the dependenceof vowelduration on number of syllables,Harris and Umeda (1974) have pointedout that it isa dominatingfactorin thecarrierphrase mode,but isnegligiblein connectedspeech.Umeda's(1975) resultssuggestthat the number of syllablesmay also influence lengtheningbefore voicing. This latter effect might therefore be expectedtoo, not only in the caseof carrier phrasemodes,but also when word lists, includinglists of
similarto thelengthening-before-voicing effectfor otherlanguages,e.g., 19% for Dutch, 22% for Korean, 18% for Russian and Norwegian. Somewhatbelow these are French
( 13% ) andSpanish( 14%), andmuchhigherthantheseare English (39%) and German (40%) (Chen, 1970; Van Dommelen, 1982). However, in comparingthese results, one must considerpotential differencesin speakingmode, speakingrate, and the phonologicalstructureof the specific languages.In the caseof both German and English,the extraordinary high percentagesare ascribedto a learned, language-specific speechcharacteristicof the phonologicalsystems (Chen, 1970; Van Dommelen, 1982). As to syllable structure, the resultsindicate that it has no effect on vowel duration
in Afrikaans.
The difference be-
tweenopenand closedsyllableswhen voicewasunspecified, was a mere 4 ms. When voicing was taken into account, vowelsprecedingvoiceless consonants werenearlyaslongin opensyllables( 142ms) asthey werein closedsyllables( 144 ms). When vowelswere followed by voicedconsonants,the differenceof 10 ms wasonly slightly greaterthan the voicelessconsonantcondition.These resultscomparefavorably with the other languagesmentionedearlier, exceptfor Italian. It seems as if the 31% difference between the vowels in
TABLE I. Averagedurations(in ms) and standarddeviations(s.d.) of all vowels(V = short;V: ----long vowelsand diphthongs),in openand closed syllables.In the former structures,vowelsare followeddirectly by syllable boundaries($), in the latter, by consonants.Voiced consonantsare indicatedasC, voiceless onesasC. N = numberof tokens;631 in total;S -- subject. Context
N
S1
S2
S3
S4
VC$
80
130
138
179
V:C$ V$C V:$C
71 80 80
173 134 197
190 146 196
VC•
80
112
V:C$ V$C
80 80
150 103
V:$C
80
162
591
Mean
s.d.
166
152
19
247 184 249
188 156 219
200 155 215
28 18 22
109
129
124
119
158 106
185 131
185 114
169 114
16 11
151
191
178
171
15
J. Acoust.Soc. Am., Vol. 92, No. 1, July 1992
8
open and closedsyllablesin that language (Farnetani & Kori, 1986), has to be attributed to a learned, languagespecificphonologicalcharacteristicof Italian, just like in English,where vowelsprecedingvoicedconsonantstend to lengthenmore than usual. The presentresultshavestronglyconfirmedthe hypothesisthat vowelsin Afrikaanswill be longerin durationin the context
of voiced
consonants
than
voiceless consonants.
However,therewasno supportfor the hypothesisthat vowelsin opensyllableswill be longerin durationthan thosein closedsyllables.Becauseof potential influencesof speech materialsand speechcontext,it would be importantto conduct a comparativestudy, in which thesesamehypotheses were testedin wordslists,carrier phrasesand in connected speech. Daan Wissing:Letters to the Editor
591
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ACKNOWLEDGMENTS
The author thanks JustusRoux, as well as the anonymous reviewersfor their constructivesuggestions for the manuscript.A specialword of thanksgoesto associate editor Ralph Ohde for invaluableeditorialcommentsand recommendations.
The financial assistance of the South African
Institutefor ResearchDevelopmenttowardsthe publication of this work is herebyacknowledged.Opinionsexpressedin thispublicaft. on and conclusions arrivedat, are thoseof the author and are not necessarilyto be attributedto the Institute for ResearchDevelopment. Balasubramanian, T. (1981). "Durationof vowelsin Tamil," J. Phon.9, 151-161.
Phonetica 7, !9-39.
Harris,M. S., andUmeda,N. (1974). "Effectof speakingmodeon temporal factorsin speech:vowel duration," J. Acoust. Soc.Am. 56, 10161018.
House, A. S., and Fairbanks, G. (1953). The influence of consonant
environmentuponthe secondaryacousticalcharacteristics of vowels,"J. Acoust. Soc. Am. 25, 105-114.
Klatt, D. H. (1976). "Linguisticusesof segmentaldurationin English: acousticand perceptualevidence,"J. Acoust.Soc.Am. 59, 1208-1221. Mitleb, F. M. (1984). "Voicingeffecton voweldurationis not an absolute universal," J. Phon. 12, 23-27.
Nooteboom,S. G. (1972). "Productionand perceptionof vowelduration. A studyof durationalpropertiesof vowelsin Dutch," PhilipsRes.Rpt. Suppl., No. 5. O'Shaughnessy, D. (1981). "A studyof Frenchvowelandconsonantdurations," J. Phon. 9, 385-406.
Chen,M. (1970)."Vowellengthvariation asafunction ofthevoicing ofthe consonantenvironment,"Phonetica22, 129-159.
Crystal,T. H., andHouse,A. S. (1982). "Segmental durations in connected speechsignals:Preliminaryresults,"J. Acoust.Soc.Am. 72, 705-716.
Crystal,T. H., andHouse,A. S. (1988a)."Segmental durations in connected speechsignals:Current results,"J. Acoust.Soc.Am. 83, 1553-1573. Crystal, T. H., and House, A. S. (1988b). "The duration of AmericanEnglish vowels:an overview,"J. Phon. 16, 263-284. Crystal, T. H., and House, A. S. (1990). "Articulation rate and the dura-
tionof syllables andstress groupsin connected speech," J. Acoust.Soc. Am. 88, 101-112.
Eefting,W. (1991). "The effectof"informationvalue"and"accentuation"
onthedurationof Dutchwords,syllables andsegments," J. Acoust.Soc. Am. 89, 4 !2-424.
Farnetani,E., andKori, S. (1986). "Effectsof syllableandwordstructure
592
on segmentaldurationsin spokenItalian," SpeechCommun.5, 17-34. Fintoft, K. (1962). "The durationof someNorwegianspeechsounds,"
J. Acoust. Soc.Am.,Vol.92,No.1,July1992
Oller, D. K. (1973). "The effectof positionin utteranceon speechsegment durationin English,"J. Acoust.Soc.Am. 54, 1235-1247. Rietveld,A. C. M., andFrauenfelder,U. H. (1987). "The effectof syllable structureon vowel duration," Proceedings of the EleventhInternational Congress onPhoneticSciences, Tallinn, 1987,Vol. 4, pp. 28-31. Slis,I. H., andCohen,A. (1969). "On thecomplexregulatingthe voicedvoicelessdistinctionI," Lang. Speech12, 80-102. Van Dommelen,W. (1982). "A contrastiveinvestigation of vowelduration in German and Dutch," Phonetica 39, 23-35.
Trommelen,M., andZonneveld,W. (1979). Inleidingin degeneratievefonologie( Coutinho,Muiderberg). Umeda,N. (1975). "Vowel durationin AmericanEnglish,"J. Acoust.Soc. Am. 58, 43• •5.
Wissing,D. P. (1982). Algemeneen Afrikaansegeneratiewe fonologie ( MacMillan, Johannesburg).
DaanWissing: Letters totheEditor
592
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 138.251.14.35 On: Tue, 23 Dec 2014 08:25:37
(Received19October1990;acceptedfor publication1 April 1992)
A productionstudywasconductedto investigatethe effectof vowellengtheningbeforevoiced obstruents,and the possibleinfluencethat the openness versusclosedness of syllableshaveon the temporalstructureof vowelsin somelanguages.The resultsrevealedthat vowelswere significantlylongerwhenfollowedby voicedconsonants than voiceless consonants. Vowel duration did not, however,vary with syllablestructure.However, vowelsin opensyllables followedby [ + voiced] consonantstendedto be longerthan when the followingconsonants were [ -- voiced].Theseresultsare discussed in the contextof currentknowledgeof other languages. PACS numbers:43.70.Fq, 43.70.Kv
INTRODUCTION
whentheseconsonants occurred in word-finalandprepausal
In this study, we focus on the duration of Afrikaans vowels in two contexts, voiced versus voicelessconsonants,
and open versusclosedsyllables.The lengthening-beforevoicingeffect,which is sometimesreferredto as shortening before voiceless consonants (Klatt,
1976), has been ob-
servedfrequently,especiallyin English.Word- and syllableboundary effecton vowel duration have been observedin a numberof languages,includingEnglishand Italian.
The phenomenonof lengthening-before-voicing was first identifiedby Houseand Fairbanks(1953) for English, and sincethen, numerousinvestigatorshave corroborated theseresults.Vowels tend to be longer when followed by voiced obstruentsthan when followed by voicelessconsonants.O'Shaughnessy ( 1981), for example,reportsthe same effectfor French, Fintort (1962) for Norwegian,Balasubramanian (1981) for Tamil, Van Dommelen (1982) for Dutch and German, and Slis and Cohen (1969) also for Dutch. Chen (1970) refers to similar results for Russian,
Korean,French, Spanish,Norwegian,and English.Klatt (1976), amongothers,claimsthisto be a universaltendency,but Mitleb (1984) arguesthat thisis not the casein Arabic. The results obtained by Crystal and House (1982)
stronglysupportthe lengthening-before-voicing effectfor longvowelsprecedingstops,but neithershortnor longvowels were lengthenedwhen followed by voiced fricatives. Crystaland House (1988a) point out that theseresultsare rather uncertain,sinceall occurrences weretallied, irrespective of word boundariesor pauses.They thereforereanalyzedthe durationsof the entiresetof longandshortvowels when followedby voicedand voicelessconsonants in word finalpositionirrespective of the post-consonantal condition, whenthe consonants wereword-finalbut not prepausal,and 589
J. Acoust.Soc. Am. 92 (1), July 1992
position(Crystal and House, 1988a). They concludedthat the lengthening-before-voicing effectis only applicableto vowelsprecedingprepausalword-finalconsonants. In the caseof Germanand Dutch, a languageclosely relatedto Afrikaans,studiesonthelengthening-before-voicing effecthave been confinedto the influencethat consonantsin intervocalic positionhaveonpreceding vowels(Van Dommelen, 1982). According to Van Dommelen the lengtheningeffectof the German intervocaliclenis (lax or voiced)stopconsonants on precedingvowelsis about65 ms (roughly40% ), andin the caseof Dutch, onlyabout19%. Slisand Cohen(1969) reporta meandifferenceof 30 msfor Dutch vowels in similar conditions.
The above-mentioned information of Van Dommelen
(1982) on Dutch andGermanalsopertainsto theeffectthat syllablestructuremight haveon the durationof vowels.Al-
thoughVan Dommelendoesnot usethe term open (or closed) syllable,his investigationexaminedvowelsoccurring in opensyllablessuchasin wordslike "hie-den" versus "hie-ten,"i.e., syllablestructure"C¾$CVC" ($ = syllable boundary). As a matterof fact,fewstudiesexplicitlyreferto syllable structurein thesense of openness andclosedness, exceptthe studiesof Farnetani and Kori (1986), and Rietveld and Frauenfelder (1987), who all statedthat vowelsare longer in open syllables (i.e., in "XV$CY" structures;X and Y = empty or representingone or more segment)than in closedsyllables("XVCSY"). In the caseof Italian, this differenceamountsto an averageof 31% (Farnetani and Kori, 1986). Contrary to these findings, Crystal and House (1990) report a tendencyfor stressedvowelsto be shorterin word-finalposition,i.e., opensyllables,than when followed by consonants.However, their data for stressedvowels in
0001-4966/92/070589-04500.80
@ 1992 AcousticalSocietyof America
589
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nonprepausal wordsindicatethat vowelsin opensyllables words,4 of the 16 wordsconsistof three syllableseach, the other12arebisyllabic.Thisseemsto beanunbalanced situaare about8% longerthan vowelsin closedsyllables(avertion as well, and could possibly have had an effect on the agesandpercentages deducedfromTable 1, p. 102), which is consistent with the results of Farnetani and Kori (1986) and Rietveld and Frauenfelder (1987). Balasubramanian (1981) found that Tamil vowels in closed syllableswere
longerwhen followedby voiceless consonants than when followedby voicedconsonants, while the oppositeoccurred in the caseof opensyllables.In thecaseof Tamil, the factors of lengthening-before-voicing and syllablestructureappear to be in close interaction with each other.
In the caseof Afrikaans, the followinghypotheseswere
outcome of the investigation.However, as Nooteboom
(1972) pointsout,whenthenumberof syllables thatremain to be producedin the wordswerekeptconstant,aswasthe casein thepresentexperiment, thiseffectiseliminated.Other factorsthat may have an effecton vowel duration are accentuation (Eefting,1991), prepausal lengthening ( Klatt, 1976), and non-word-finalshortening(Oller, 1973). In the presentexperiment, thesefactorswereheldconstant asfaras possible.
formulated:
( 1) Afrikaans vowels,when followedby voicedconson-
B. Subjects, testing and measuring procedures
ants,will belongerthanwhenfollowedby voiceless conson-
Four nativespeakersof Afrikaans,two of eachsex,participatedon a voluntarybasisand were not paid for their (2) Afrikaans vowelsin open syllableswill be longer services. The taperecordingsweremadein a professionally than vowelsin closedsyllables. equippedstudio.Each subjectread the list of 16 stimulus words,ten randomizedtimesat a normalspeakingrate. The stimuluswords containingthe regressiveassimilationrule I. METHOD wereclearlyindicatedfor the subjects'pronunciation.Those A. Stimulus material formsthat had not beenassimilatedproperlywererepeated. Sixteenstimuli were used,includinglong versusshort Of the 640 stimuli (4 subjectsX 10 readingsX 16 stimulus vowels,open versusclosedsyllables,and voicedversus words) only nineproductionswererejectedduringthe meavoicelessconsonants.Fricatives were equally distributed. surementphase. The vowel[a:] andthediphthong[o9i]represented thelong vowels(seeNooteboom,1972,for thegroupingof longvowC. Measuring procedures and criteria elsanddiphthongs intooneclass),and [a] and [e] repreTherecordedspeech tokensweredigitizedat a sampling sentedthe shortones.The consonantsfollowingthe vowels rate of 16 kHz and waveformsdisplayedon a computerterwere the voicelessfricatives, [f] and [s], and their voiced minal.Segmentation wascarriedout,anddurationsof vowcognates[v] and [z]. In the caseof syllablesclosedby elswereestablished usinga segmentation programwith auvoicedfricatives,thevoicingresultedfromtheapplicationof ditoryfeedback.The vowelonsetcoincidedwith the endof anoptionalphonological ruleof regressive assimilation of a thepreceding stopsor fricatives. The endof theunaspirated followingvoicedstop[d], whichoccurredat thebeginning stop( [k] in eachcase)wasmarkedafterthereleaseburst, ofthenextsyllable.Thiswasnecessary in viewof theabsence and that of the voicelessfricative ( [ s] or [ f] ) at the end of of voicedobstruentsin syllable-or word-finalpositionin nonperiodic noise.The offsetof vowelscorresponded with Afrikaans,like in manyGermaniclanguages, dueto a pho- thebeginning of thefricatives. In thecaseof thevoiceless [f] nological ruleof devoicing in thatposition(Trommelenand and [s] thiswaseasilydetectedat the pointwherea decrease Zonneveld, 1979;Wissing,1982). in amplitudeappearedcoinciding with thebeginning of nonThusthe completesetof stimuluswordswerethe fol- periodicnoise.Theendof vowelspreceding thevoicedfricalowing (the relevant phoneticinformationappearsin tives [z ] and [ v ] weretakento be the pointat which there
ants.
squared brackets;[a] and [e] = shortvowels;[a:] = long vowel,[o9i ] = diphthong consisting ofschwad- [i ]; $ = syllable boundary):
"õesk[a:$v]e"("chafed"), "besk[a:v$]de"("civilized"), "gesk[a:$f]ie" ("moderate chafing"), "besk[a:f$]te"
wasa suddendrop in amplitudeand high frequencyenergy in the waveform (Fig. 1).
II. RESULTS
("civilized", variant of "besk[a:v$] de"); "v [o9i$v ] e", ("fives"), "v [o9i$v ] de", ("fifth"), "v [ o9i$f]ie" ("little five"), v[o9iSf]tig"("fifty"); "s[eSz]e" (substandard form of"s [eS] se"sixes"),"s[ez$] de" ( "sixth"), "s[eS] si" ( "little six"), "s[ess] tig" ("sixty); "k [aSz] e" (substandard form of"k [ ass] e "boxes"), "k [ass] tig" ("make-believe"), "k [az$] dig" ("box-tight"), "k [ass] i" ("little box").
arrangedby syllabletypefor eachsubject.In general,the effectsof syllablestructureand consonantvoicingappear relativelyconsistentacrosssubjects.
The long vowelsare followedby either voiceless[f] or voiced[ v ], and the shortvowelsby either [ s] or [ z ]. These
As shown in Table II, the differencesbetween vowel durationswhenfollowedby voicedversusvoiceless conson-
unbalancedconsonantalcontextsacrosslongand shortvow-
ants were significant.For vowelspooledacrosssyllable
els werenecessary becauseof the unavailabilityof suitable setsof existingwordsin whichthepresenthypotheses could be tested. As to the number of syllablesin the stimulus
structure the difference was 36 ms (20%)
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J. Acoust.Soc.Am.,Vol.92, No.1, July1992
The mean durations of the vowels are shown in Table I,
A. Consonant voicing
[F(1,56)
= 28.05,p = 0.0001]. In opensyllables only,thedifference was 42 ms (22%) [F(1,28) = 25.41,p = 0.0001], and in DaanWissing: Lettersto theEditor
590
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TABLE II. Interaction of vowel duration (in ms) as a function of conso-
[.8
nantvoicingandsyllablestructurefor all vowelsacrosssubjects(N = 631).
Consonantvoicing
li
•
!
-1. Zoo•e• dis•la• 0.1087S
Bcr: 0.1371S
Cr: 0. Z636S
d i for:
0.1265S
21 Ecr: 0. Z639S
E: 0. 3387S
Syllablestructure Open Closed
X
q- Voiced
184
174
179
-- Voiced
142
144
143
X
163
159
3
closed syllables only, the difference was 30 ms (17%) [F(1,28) = 7.82,p -- 0.0092].
minimal pairs are used.On the other hand, it might be absent,or largelyabsent,whenconnectedspeechmaterialsare used.A numberof investigations includingthe presentstudy are of the former type (House and Fairbanks, 1953;Fintoft, 1962; Van Dommelen, 1982; Balasubramanian, 1981), while the experimentsof Crystal and House ( 1982, 1988a, 1988b, 1990) are of the latter type. Accordingto the presentresults,the overall difference
B. Syllable structure
between vowel duration in the context of voiced versus voiceless consonants is about 20% for Afrikaans. This is
FIG. 1. Oscillogramof a portion of the word "s[ez]de." The vowel/e/ occursbetweenthe two verticaldottedand partiallydottedlines(indicated as 1 and 2). The first part of the voicedfricative/z/ liesbetween2 and 3.
As illustrated in Table II, the differencebetween vowel
duration in openand closedsyllablescollapsedacrossvoicing (4 ms, or 2%) was not significant [F(1,56)=0.38, p=0.5383]. Moreover, syllable structure (open versus closedsyllable) was not significantfor either voicedconsonant environment[F(1,28) = 0.99, p = 0.3286] ) or voicelessconsonantenvironment [F(1,28) -- 0.04, p -- 0.8516]. III. DISCUSSION
AND CONCLUSION
The resultsof this experimentdemonstrateadequately that the lenghtening-before-voicing effectis presentin Afrikaans,thussubscribing to the claimof the universalityof this phenomenon.With regardto the dependenceof vowelduration on number of syllables,Harris and Umeda (1974) have pointedout that it isa dominatingfactorin thecarrierphrase mode,but isnegligiblein connectedspeech.Umeda's(1975) resultssuggestthat the number of syllablesmay also influence lengtheningbefore voicing. This latter effect might therefore be expectedtoo, not only in the caseof carrier phrasemodes,but also when word lists, includinglists of
similarto thelengthening-before-voicing effectfor otherlanguages,e.g., 19% for Dutch, 22% for Korean, 18% for Russian and Norwegian. Somewhatbelow these are French
( 13% ) andSpanish( 14%), andmuchhigherthantheseare English (39%) and German (40%) (Chen, 1970; Van Dommelen, 1982). However, in comparingthese results, one must considerpotential differencesin speakingmode, speakingrate, and the phonologicalstructureof the specific languages.In the caseof both German and English,the extraordinary high percentagesare ascribedto a learned, language-specific speechcharacteristicof the phonologicalsystems (Chen, 1970; Van Dommelen, 1982). As to syllable structure, the resultsindicate that it has no effect on vowel duration
in Afrikaans.
The difference be-
tweenopenand closedsyllableswhen voicewasunspecified, was a mere 4 ms. When voicing was taken into account, vowelsprecedingvoiceless consonants werenearlyaslongin opensyllables( 142ms) asthey werein closedsyllables( 144 ms). When vowelswere followed by voicedconsonants,the differenceof 10 ms wasonly slightly greaterthan the voicelessconsonantcondition.These resultscomparefavorably with the other languagesmentionedearlier, exceptfor Italian. It seems as if the 31% difference between the vowels in
TABLE I. Averagedurations(in ms) and standarddeviations(s.d.) of all vowels(V = short;V: ----long vowelsand diphthongs),in openand closed syllables.In the former structures,vowelsare followeddirectly by syllable boundaries($), in the latter, by consonants.Voiced consonantsare indicatedasC, voiceless onesasC. N = numberof tokens;631 in total;S -- subject. Context
N
S1
S2
S3
S4
VC$
80
130
138
179
V:C$ V$C V:$C
71 80 80
173 134 197
190 146 196
VC•
80
112
V:C$ V$C
80 80
150 103
V:$C
80
162
591
Mean
s.d.
166
152
19
247 184 249
188 156 219
200 155 215
28 18 22
109
129
124
119
158 106
185 131
185 114
169 114
16 11
151
191
178
171
15
J. Acoust.Soc. Am., Vol. 92, No. 1, July 1992
8
open and closedsyllablesin that language (Farnetani & Kori, 1986), has to be attributed to a learned, languagespecificphonologicalcharacteristicof Italian, just like in English,where vowelsprecedingvoicedconsonantstend to lengthenmore than usual. The presentresultshavestronglyconfirmedthe hypothesisthat vowelsin Afrikaanswill be longerin durationin the context
of voiced
consonants
than
voiceless consonants.
However,therewasno supportfor the hypothesisthat vowelsin opensyllableswill be longerin durationthan thosein closedsyllables.Becauseof potential influencesof speech materialsand speechcontext,it would be importantto conduct a comparativestudy, in which thesesamehypotheses were testedin wordslists,carrier phrasesand in connected speech. Daan Wissing:Letters to the Editor
591
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ACKNOWLEDGMENTS
The author thanks JustusRoux, as well as the anonymous reviewersfor their constructivesuggestions for the manuscript.A specialword of thanksgoesto associate editor Ralph Ohde for invaluableeditorialcommentsand recommendations.
The financial assistance of the South African
Institutefor ResearchDevelopmenttowardsthe publication of this work is herebyacknowledged.Opinionsexpressedin thispublicaft. on and conclusions arrivedat, are thoseof the author and are not necessarilyto be attributedto the Institute for ResearchDevelopment. Balasubramanian, T. (1981). "Durationof vowelsin Tamil," J. Phon.9, 151-161.
Phonetica 7, !9-39.
Harris,M. S., andUmeda,N. (1974). "Effectof speakingmodeon temporal factorsin speech:vowel duration," J. Acoust. Soc.Am. 56, 10161018.
House, A. S., and Fairbanks, G. (1953). The influence of consonant
environmentuponthe secondaryacousticalcharacteristics of vowels,"J. Acoust. Soc. Am. 25, 105-114.
Klatt, D. H. (1976). "Linguisticusesof segmentaldurationin English: acousticand perceptualevidence,"J. Acoust.Soc.Am. 59, 1208-1221. Mitleb, F. M. (1984). "Voicingeffecton voweldurationis not an absolute universal," J. Phon. 12, 23-27.
Nooteboom,S. G. (1972). "Productionand perceptionof vowelduration. A studyof durationalpropertiesof vowelsin Dutch," PhilipsRes.Rpt. Suppl., No. 5. O'Shaughnessy, D. (1981). "A studyof Frenchvowelandconsonantdurations," J. Phon. 9, 385-406.
Chen,M. (1970)."Vowellengthvariation asafunction ofthevoicing ofthe consonantenvironment,"Phonetica22, 129-159.
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Crystal,T. H., andHouse,A. S. (1988a)."Segmental durations in connected speechsignals:Current results,"J. Acoust.Soc.Am. 83, 1553-1573. Crystal, T. H., and House, A. S. (1988b). "The duration of AmericanEnglish vowels:an overview,"J. Phon. 16, 263-284. Crystal, T. H., and House, A. S. (1990). "Articulation rate and the dura-
tionof syllables andstress groupsin connected speech," J. Acoust.Soc. Am. 88, 101-112.
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Oller, D. K. (1973). "The effectof positionin utteranceon speechsegment durationin English,"J. Acoust.Soc.Am. 54, 1235-1247. Rietveld,A. C. M., andFrauenfelder,U. H. (1987). "The effectof syllable structureon vowel duration," Proceedings of the EleventhInternational Congress onPhoneticSciences, Tallinn, 1987,Vol. 4, pp. 28-31. Slis,I. H., andCohen,A. (1969). "On thecomplexregulatingthe voicedvoicelessdistinctionI," Lang. Speech12, 80-102. Van Dommelen,W. (1982). "A contrastiveinvestigation of vowelduration in German and Dutch," Phonetica 39, 23-35.
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