A comparative acoustic study of English and Spanish vowels
Ann R. Bradlowa)
Cornell University,Departmentof ModernLanguagesandLinguistics,
Ithaca,New York14853
(Received
30 November1993;accepted
for publication
14 November1994)
Languages
differ widelyin the sizeof theirvowel inventories;
however,cross-linguistic
surveys
indicatethat certainvowelsand vowel systemconfigurations
are preferred.A cross-linguistic
comparison
of the acoustic
vowelcategories
of two languages
thatdifferin vowelinventorysize,
namely,EnglishandSpanish,
wasperformed
in orderto revealsomeof thelanguage-specific
and/or
universalprinciplesthatdeterminethe acousticrealizationof thevowelsof thesetwo languages.
Thiscomparison
showsthatthepreciselocationin theacoustic
spaceof similarvowelcategories
acrossthetwolanguages
is determined,
in part,by a language-specific
base-of-articulation
property.
Thesedata also suggestthat the relativelycrowdedacousticvowel spaceof Englishmay be
expandedwith respectto the relativelyuncrowdedacousticvowelspaceof Spanish;however,this
effectis variabledepending
on the syllablecontextof theEnglishvowels.Finally,the dataindicate
no differencein the tightnessof within-category
clusteringfor the largeversusthe smallvowel
inventory.
PACS numbers: 43.70.Hs, 43.70.Kv
INTRODUCTION
I. GENERAL APPROACHES
VOWEL INVENTORIES
Surveysof segmentinventories
indicatecross-linguistic
preferences
for certainvowelsand for certainvowel inventory configurations.
For example,in a surveyof 317 languages,Maddicson(1984) finds that vowel inventoriesin
thissamplevary from havingthreeto fifteendistinctvowel
qualities,with two-thirdsof the languages
havingbetween
five andsevendistinctvowelqualities.
Additionally,
thespecific vowelsthatcomprisethesestatistically
preferredvowel
inventoriestend to be the same.For example,five-vowel
systemstendto have/i,e,a,o,u/,seven-vowelsystemstendto
have thesefive vowelsplus/e/and/o/, and six-vowelsystems usuallyhave/i,e,a•,o,o,u/.Furthermore,the vowel inventoriesof the vast majorityof the world'slanguagesincludethethreevowelsthatdefinetheextremesof thegeneral
vowelspace,namely/i,a,u/.Accordingly,
thesethreevowels
are knownas the "point vowels,"andhavebeenaffordeda
specialstatusin theoriesof vowel systems.
Thesecross-linguistic
tendencies
haveled to thehypothesisthatthereare constraints
on possiblespeechsoundsand
their cooccurrence,
which have their sourcein generallinguistic,or physical(i.e., auditoryand articulatory)constraints. However, the exact nature of these constraintsand
theirinteractionthatproducesthe observedinventoriesis not
yet fully understood.
This studyis thusmotivatedby a general interestin the effect of inventorysize on the acoustic
TO THE STUDY OF
Previouswork has led to the developmentof several
theoreticalpositionsregardingthe structureof vowel systems.Dispersion
theory(DT) claimsthatspeechsoundsare
selected
via constraints
thatarebasedon a principleof sufficientperceptualcontrast.In this theorythe vowelsof a
givenlanguageare arrangedin the acousticvowelspaceso
as to minimizethe potentialfor perceptualconfusionbetween the distinctvowel categories.Using computerprogramsto generatethe optimalconfigurations
for vowel systemsof varioussizes,thisapproachto vowel inventorieshas
provedfairly successful
(Liljencrantsand Lindbiota,1972;
Lindblom,1975, 1986; Disnet, 1984). Howevertheseinvestigationsof DT focusexclusivelyon intercategory
distance
as the determinerof vowelsystemconfiguration
in a universallydefinedacousticvowel space.As a result,thisapproach
fails to accountfor the observation
that certainlanguages,
such as Swedish with nine vowels and Danish with ten vow-
els, crowd their vowels into a small corner of the entire
vowel space rather than dispersingthem throughoutthe
availablespace(Disnet,1983).In morerecentdevelopments,
the dispersionprinciplehasbeenexpressedas a principleof
sufficient,rather than maximal, contrast(Lindbiota, 1989,
1990).Furthermore
thetheoryhasbeenextended
to account
for within-speaker
variation.For example,Moon andLindvowel spacesof differentlanguages,
andin how thiseffect blom,1989)showthatundercircumstances
thatrequireclear
might reveal someof the universaland/orlanguage-specific speech,a speaker's
vowelspacewill be expandedrelativeto
constraints
leadingto the observedpatternsin soundinvenhis or her casualspeechvowel space.
toriesof the languages
of the world. Specifically,thispaper
In a studythataddresses
the predictionof DT thatvowexploresthe effectof inventorysize on the acousticrealizaels will be maximallydispersed
in the acousticspace,Jongtion of vowels in a languagewith a relativelylarge vowel
man et al. (1989) comparedthe relativelycrowdedvowel
inventory,GeneralAmericanEnglish,and in a languagewith
spacesof English (with 11 monophthongs)
and German
a relativelysmallvowel inventory,Madrid Spanish.
(with 14 monophthongs)
with the relatively uncrowded
vowel spaceof Greek(with just 5 monophthongs).
These
authors
found
that
the
crowded
vowel
spaces
of
English
and
a)Current
affiliation:
Speech
Research
Laboratory,
Psychology
Department,
IndianaUniversity,Bloomington,
IN 47405.
Germanare expandedrelativeto the uncrowdedvowel space
1916 J. Acoust.Soc. Am. 97 (3), March 1995
0001-4966/95/97(3)/1916/9/$6.00
¸ 1995 AcousticalSocietyof America 1916
of Greek.
1 Jongman
etal. plotted
thevowels
of these
lan-
of JohnWallisin 1653 (set:Kemp,1972).However,within
thetraditionof generarive
phonology,
theideaof a language(1989).Thisrepresentation
scheme
is designed
to normalize specificarticulatorysettinghasoftenbeenconsidered
outside
thedatapoi.nts
forbothinter-andintraspeaker
differences
by of the areaof interestof theoreticallinguistics.For example,
representing
speechsounds
in termsof log ratiosof thefuninTheSound
Pattern
ofEnglish,
Chomsky
andHalle(1968)
damentalfrequencyandthe firstthreeformants.The results consider
thisaspectof speechasextragrammatical,
andthus
of thisstudysupport
thehypothesis
thattheacoustic
realiza- as partof the performance
aspectof language,
ratherthan
tion of vowelcategories
is dependent
on inventorysize and part of the grammatically
determined
competence
aspect.
Nevertheless,severalinvestigatorshave pointedto the
suggestthat someversionof the dispersionprincipledoes
indeedhold true acrosslanguages:the largerthe inventory, importance
of thenotionof a base-of-articulation
for providthe more"expanded"the acousticvowel space.
ing insightfulanalysesof both phonologicaland phonetic
The quantaltheoryof speech(QTS) (Stevens,1972, observations.
In studiesthat have testedthe predictionsof
1989) suggests
an alternativeapproach
to vowel systems. DT andQTS, phoneticdifferences
betweensimilarsegments
This theoryis basedon the observation
that for certainpaof differentlanguageshave often beenobserved.For exrametersof the articulatorydomain,thereis a nonmonotonic ample,LindauandWood (1977) investigate
the vowelsof
relationbetweenvariationin the articulatoryconfiguration threerelatedNigerianlanguages,
Yoruba,Edo, andGhotuo,
all of whichhavephonemically
equivalentseven-vowel
sysandits acousticconsequences.
Similarly,certainchanges
in
theacoustic
signaloversomepartof therangeof a particular tems,andfind thatthe vowelspacesof Edo andGhotuoare
parameter
arenonmonotonically
relatedto thecorresponding very similar.Holyever,contraryto the predictionof the dispersionprinciple,the vowel spaceof Yorubadeviatesfrom
auditoryresponse
of thelistener.In otherwords,according
to
the structureof the othertwo seven-vowelsystemsandis not
this theory,thereare certainregionsof stabilityin the phoSimilarly,Disnet(1983) findsthatthe
neticspace.In particular,it is claimedthatthereare stable maximallydispersed.
seven-vowel
systemsof YorubaandItaliandiffer from each
regionscorresponding
to the pointvowels/i/,/a/, and/u/.
other in their locations of the seven vowels in the acoustic
Thusthistheorypredictsthatthe pointvowelsshouldbe in
space.Disnet documentsadditionalcasesof systematicdifapproximately
the samelocationsacrossall languages,regardlessof vowel inventorysize. Furthermore,QTS predicts ferencesacrossthe vowelsof severalGermaniclanguages;
that, sincethe point vowels are in phoneticallystablerefor example,shefindsthatthevowelsof Danishare systemgions,theyshould
showlesswithin-category
variability
than atically articulatedwith a highertongueposition,as it is
reflectedby F1, thanthe vowelsof English.Disnetclaims
nonpointvowels.
Evidencethatcertainchangesin the articulatorydomain that thesedata demonstratethe role of a language-specific
propertyin the phoneticrealizationof
are nonmonotonically
relatedto their acousticconsequences base-of-articulation
comesfrom the observation
thatthereare acousticproperties vowelphonemes.
In particular,thistypeof language-specific
guagesin the auditory-perceptual
spaceproposedby Miller
whicharerelatively
insensitive
to arficulatory
perturbation. effect
is seen in across-the-board shifts of the vowels of one
For example,in thecaseof nonlowfrontvowelswhichhave
a frontedtonguebody,the locationsin the frequencyspectrum of the second,third, and fourth prominencesare rela-
languagerelativeto similarvowelsin anotherlanguage.
In light of the theoreticalclaimsand experimentalevidencediscussed
above,theFresentstudywasundertaken
asa
tivelyinsensitive
toperturbation
inthetongue-body
position direct means of assessingthe contributionsof languagealongtheanterior-posterior
dimension
(Stevens,
1989).For specificandgeneralunivers:dprinciplesin the acousticrealthisrange,F2 is at a maximumandis within a few hundred izationof vowel categoriesacrosslanguageswith relatively
hertz of F3. In contrast,the frequencyof F1 variesmono- large versussmall vowel inventories.Englishand Spanish
tonicallywith the size andpositionof the articulatorycon- were chosenfor this studybecauseof the large difference
striction.This resultis presented
by Stevensas evidenceof a
between the sizes of their vowel inventories:English has
stableregionin thiscornerof thevowelspace,whichcorre- more than doublethe numberof stressedmonophthongal
spondsto thepointvowel/i/. Furthermore,
in an articulatory vowelsthanSpanish.Additionally,the five-vowelsystemof
studyof/i,a,u/ in GeneralAmericanEnglish,Perkelland Spanishis statistically
very common,whereasthe 11-vowel
Cohen(1989) findthatfor eachof thesevowelsthereis both systemof Englishis uncommonly
large(Maddieson,
1984).
an articulation-to-acoustic
saturationeffect, and a muscle Furthermore,
the vowel systemsof thesetwo languages
are
contraction-to-displacement
saturation
effect.In otherwords, similarin thattheyvaryalongthesamedimensions
(neither
theseauthorsfind thatovera rangeof changesin the articu- languagehascontrasfive
rounding,length,or nasalization).
lationof thesevowels,theacousticoutputis relativelystable. Consequently,
the principaldifferencebetweenthesevowel
DT and QTS bothproposegeneraluniversalprinciples systemsis in the number of vowels. Thus this Englishto accountfor the observedcross-linguistic
tendenciesreSpanishcomparison
represents
a comparison
of anunusually
gardingvowel inventorysize and structure.In contrastto
large vowel inventory with a smaller cross-linguistically
theseapproaches,
the notionof a language-specific
base-of- commonvowel inventory.T•e expectationis thatthisdifferarticulationis presentedas an accountfor the observation encebetweenthe two vowel inventorieswill highlightboth
that similar soundsacrosstwo languagescan differ due to a
the differences and similarities attributable to languageconsistent,
language-specific
adjustmentof the articulators. specificand/oruniversalaspectsof vowel production.
Thisnotionhasbeena partof thetraditional
phoneticliteraIn this comparison,vowel formantmeasurements
from
tureovertheages:Disnet(1983)citesits originasthework eachof the two languagesare evaluatedin termsof the pre1917 J. Acoust.Soc.Am., Vol. 97, No. 3, March1995
A. Bradlow:Comparativestudyof Englishand Spanishvowels 1917
TABLE I. SpanishCVCV, EnglishCVC, andEnglishCVCV meanvowelformantsin hertzwith standard
deviations.
SpanishCVCV
EnglishCVC
F1 (s.d.)
F2 (s.d.)
F1 (s.d.)
F2 (s.d.)
286(6)
458(42)
638(36)
460(19)
322(20)
2147(131)
1814(131)
1353(84)
1019(99)
992(121)
268(20)
463(34)
430(45)
635(53)
777(81)
640(39)
780(83)
620(72)
482(30)
481(36)
326(26)
2393(239)
1995(199)
2200(168)
1796(149)
1738(177)
1354(134)
1244(145)
1033(135)
1160(47)
1331(161)
1238(160)
dictionsof the variousapproaches
to vowel inventories.
First,thelocations
of thefourcommon
vowelsarecompared
in orderto revealanybase-of-articulation
effect.Second,the
rangeand degreeof within-category
variancefor vowelsin
eachof thelanguages
arecompared
in orderto determinethe
effect of inventorysize on the generaldispersionof the
vowelcategories.
In general,theseacoustic
dataareanalyzed
in relationto theproposals
in the literature,andwith regard
to identifying the language-specificand language-
EnglishCVCV
i
I
e
•
•
n
o
•
o
o
u
FI (s.d.)
F2 (s.d.)
264(34)
429(20)
424(39)
615(60)
773(62)
655(43)
783(155)
614(65)
473(13)
411(17)
316(43)
2268(207)
1831(173)
2020(149)
1665(143)
1640(169)
1216(75)
1182(152)
945(83)
1094(41)
1361(94)
1183(153)
Hz andlow-passfilteredat 6000 Hz. All measurements
were
madeusingtheEntropics
WAVES+speechanalysissoftware
on a SUN workstation.
BothLPC spectraandspectrograms
were usedto determinethe first threeformantfrequencies.
The LPC spectrawere calculatedfrom a 25-ms Hanning
windowin thevowelsteadystate.In mostcasesan analysis
order of 14 was used;however, in a small number of cases
the analysisorderwas loweredto 12 so that the data were
smoothed
to yield a clearerpeak.The steady-state
portionof
independentfactors that affect the acousticrealization of
the vowelwasdetermined
by firstplacingtwo verticalcursotsin thespectrogram:
thefirstcursormarkedtheendof the
formanttransitions
comingout of the initial consonant,
and
II. METHOD
thesecondcursormarkedthebeginning
of theformanttransitionsinto the final consonant.
The periodbetweenthe two
Wordsexemplifyingthe 11 vowel contrasts
of English
cursorsthusindicatedtheportionof thevowelwhichshowed
and the five vowel contrasts
of Spanishwere selectedsuch
A 25-msHanningwinthatthetargetvowelsall occurbetweeneither/p/or/b/, and no (or verylittle)formantmovement.
dow
was
placed
approximately
in
the
middleof thissteady/t/. The Englishwordsare all monosyllabic
(beat,bit, bait,
state
period.
The
formant
values
were
then read from the
bet, bat,pot, bought,boat,put, boot,but), andin accordance
LPC
spectrum
and
checked
with
readings
from the spectrowith Spanishphonotadtics
and syllabification,the Spanish
gram. In the casesof English/e/and/o/, which are somewordsaredisyllabic(bita,beta,bata,bota,puta).The words
timesdiphthongized,
the formantmeasurements
were taken
wereembedded
in framesentences
thataresimilarin length,
from the portionof the vowelbeforethe offglide.The audisyntacticstructure,
andpositionof thetargetwordacrossthe
in
twolanguages.
TheEnglish
andSpahish
framesentencestory quality of this portionof the vowel was assessed,
order
to
insure
that
the
formant
measurements
being
rewere
"Say _ again"
and
"Escribe _ bien"
for/e/or/o/rather thanfi•r the
("Write _ well"),respectively.
A listof thesesentences
was cordedwerethoseappropriate
/j/
or
/w/
offglides.
The
fundamental
frequency
wasfoundby
constructedfor eachlanguagesuchthat eachsentencewas
taking
the
inverse
of
the
mean
of
three
peak-to-peak
durarepeatedfive times in randomorder, and the subjectswere
tionsfrom the centralportionof the targetvowel waveform.
instructed
to readthe sentence
list from theirrespective
lanvowels.
guageswith normalspeedand intonation.Four male speakers of GeneralAmericanEnglishandfour malespeakers
of
Madrid Spanishservedas subjects,giving a total of 20 tokens(four speakers
X five repetitions)
for eachvowel category of eachlanguage.All of the Englishspeakershave
spentmostof their lives in the Ithaca,New York area.All of
the Spanishspeakerscomefrom Madrid: two of thesehave
spentsignificantamountsof time in the U.S.; the othertwo
havespentalmostall of their lives in the Madrid area.
All recordingswere made with a portablecassetterecotder(MarantzPMD222) and an AKG D310 microphone.
The English recordingswere made in a sound-attenuated
boothin the Phonetics
Laboratoryat CornellUniversity.The
Spanishrecordingswere made in a quiet room in Madrid.
The recordings
weredigitizedwitha sampling
rateof 12 000
1918
J. Acoust. Soc. Am., Vol. 97, No. 3, March 1995
IlL RESULTS
TableI givesthe meanF1 andF2 valueswith standard
deviations
for the datafrom thefour maleSpanishspeakers
(SpanishCVCV) andfrom the four maleEnglishspeakers
(English
CVC).2In thistable,andin allsubsequent
analyses
of thesedata,the standarddeviationsrepresentthe variance
of the meansof the five tokensfor eachof the four speakers
for each language.The measurements
of the five tokens
within each subjectare treatedas repeatedmeasuresand
thereforeaveragedfor the purposesof the cross-language
comparisons.
The followingsubsections
discusstheseresultsandtheir
bearingon the approaches
to vowel inventoriesdiscussed
in
Sec. I above.
A. Bradlow:Comparativestudy of Englishand Spanish vowels 191{I
/i/
ß English
CVCV
ß English
CVC
ß Spanish
CVCV
2200
2o00
O
Greek CVCV
els wouldthusseemto concurwith the resultwe mightexpectfromanexpansion
effect.However,we alsofindthatthe
Englishbackvowels,namely/u/and/ol, areraisedin theF2
dimension
relativeto theSpanish
backvowels,resulting
in a
morecentrallocationfor the Englishbackvowels.This result for the back vowels is in contradiction to the result we
mightexpectfrom an expansion
effect,sincesuchan effect
should
result
in
English
back.
vowels
with lowerF2 frequen1600
ciesthantheirSpanishcounterparts.
This consistent
upward
shift in the F2 dimensionof the Englishvowelsrelativeto
theSpanishvowelsis in accordance
with the resultwe would
1200
expectfrom a language-specific
base-of-articulation
effect.
1000
Specifically,this resultsuggeststhat the vowelsof English
/ul •
/ot
are articulatedwith a frontedtonguepositionrelativeto the
tonguepositionfor the Spanishvowels.
200
300
400
500
600
700
An alternativeexplanationfor the higherF2 of the EnF1 (Hz)
glishvowelsrelativeto the Spanishvowelsis that the four
individual English speakersin this study all have shorter
FIG. 1. Comparison
of theareasin theF1 XF2 spacecoveredby English
vocaltractsthanthefourindividualSpanish
speakers,
result(CVCandCVCV contexts),
Spanish,
andGreek/il,/el,/o/, and/u[.Greek
ing
in
generally
higher
formants
for
the
English
speakers
datafromJoegroan
et el. (1989).
thanfor theSpanishspeakers.
In sucha situation,thepresent
datawouldalsoshowa systematic
raisingof theF1 frequenA. Base of articulation
ciesfor the Englishspeakersrelativeto the F1 frequencies
The firstissueaddressed
by thisacousticstudyconcerns for the Spanishspeakers.However,if thepresentdatado not
show a similar effect for F1 as for F2, then we can rule out
the generalplacementof the Englishand Spanishvowelsin
the acousticvowel space.In this regardwe might expect thepossibilitythatthedifferencein F2 for thetwo groupsof
speakers
is a functionof vocaltractlength.
both a language-specific
effect, which will cause similar
As seenin Fig. 1, English/i/is lowerin F 1 thanSpanish
vowelcategories
acrosstwo languages
to differ in a system/i/, and English/e/tends towardsa lower F1 than Spanish
atic way dueto a consistent
language-specific
adjustment
of
/el. However,for the back •,owels,EnglishIo/is higherin
the articulators,as well as a generalexpansioneffect for
F1
thanSpanish/o/,and English/u/and Spanish/u/do not
languageswith crowdedinventoriesrelative to languages
showanydifferencein Fl. Indeed,in anANOVA comparing
with uncrowdedinventories.
Thesetwo possibleeffectson
in EnglishandSpanishfor thefour comvowel locationwould necessarily
interactwith eachother; theF1 frequencies
mon
vowels,
the
main
effectof language
[F(1,3)=0.277,
thusit is importantto examineeachindividuallyin orderto
p=0.603]
fails
to
reach
significance,
as
does
thelanguage
assessthe extentof the two separateeffects.In this section,
Xvowel
interaction
[F(1,3)=
1.236,
p=0.3184].
Thusin
then,the focusis on assessing
the presence
(andextent)of
the F1 dimensionwe do not find a consistenteffect as we do
any language-specific
base-of-articulation
effect,whichmay
in theF2 dimension.Sincethesedatado not indicatea sysresultin a generalshift in somedirectionof all thevowelsof
tematic
raisingof all the Englishformantsrelativeto the
one languagerelativeto the equivalentvowelsof the other
Spanish
formants,an accountof differentvocaltractlengths
language.
between
the two groupsof speakers
canbe ruledout.
A comparison
of the locationsof the commonvowels
acrossEnglishandSpanish,namely/i/,/e/,/o/, and/u/, indicates a generalupward shift in the F2 dimensionof the
B. English CVCV tokens
Englishvowelsrelativeto the Spanishvowels(seeFig. 1).
The low vowel is excluded form the set of common vowels
Recall that the English vowel tokensall occurredin
becausefor theseSpanishspeakers,the low vowel is central monosyllabicwordswhereasthe Spanishtokensall occurred
in thefront-backdimension
(asrepresented
by theIPA sym- in disyllabicwords.It is thuspossiblethatthe consistentshift
bol/a/), whereas,
for theseEnglishspeakers,
thereis a low in F2 of theEnglishvowelsrelativeto theSpanishvowelsis
frontvowel (IPA/a:/) anda low backvowel (IPA/a/) but no
dueto a moregeneraleffect,suchasthe syllabicstructureof
low centralvowel. A two-factorANOVA with language the testwords,ratherthandue to a language-specific
base(Spanish,
English)andvowel(thefour commonvowels)as of-articulationproperty.For instance,
it is possiblethat the
factors,andF2 as the dependentvariable,confirmsthis imtautosyllabic
coronal,with it.,;characteristically
highF2 1opression
by showinga signific•ntmain effectfor language cos, in the Englishtest wonts raisedthe F2 of the target
[F(1,3)=24.17, p<0.001]. Thelanguage
X vowelinteractionis notsignificant
[F(1,3) = 0.942, p= 0.4358].
The effect of this differencein F2 betweenthe English
andSpanishvowelsis thatthe Englishfrontvowels,namely
/i/and/e/, arelocatedmoreperipherallyin theacousticspace
thanthe Spanishfrontvowels.This effecton the frontvow1919 J. Acoust.Soc.Am., Vol. 97, No. 3, March 1995
vowel, especiallyin the caseof the back vowels which are
generallycharacterized
by low secondformants.
Thereforein
order to assessthe effect of word structure, a new set of
Englishrecordingswas madeusingdisyllabicnonwordsthat
matchedthe syllabic structure,as well as the segmental
structure,of theSpanishtestwords.This new setof datathus
A. Bradlow:Comparativestudyof F_nglish
and Spanishvowels 1919
allowedfor a directcomparison
of the tokenswith the same
syllabicstructureas producedby speakersof the two languages.
Three of the four male speakersof GeneralAmerican
Englishfrom the first experimentproduceddisyllabicnonword versionsof the tokensused in the original data set.
These test tokens were embedded in the same frame sentence
as usedin the first experiment,and the speakersread each
sentence
five timesin randomorder.The speakers
readthese
sentences from a list that was constructed as follows:
the
word from the originallist that containedthe targetvowel
appearedon oneline, andthe framesentence
with the target
nonwordappearedon the followingline. In orderto reinforce the disyllabicityof the test tokens,and to avoidthe
productionof a flap for the roedial/if, the targetnonword
wastypedwith a periodseparating
the two syllables(e.g.,
bea.ta), andthe speakers
wereinstructed
thatthe periodindicateda syllableboundaryandto avoidproducinga flap for
the intervocalic/if. This procedurewas effectivein eliciting
tokensthat matchedtheir Spanishcounterpartsat both the
segmentaland intonationallevels.
Thissetof datawascollectedandanalyzedidenticallyto
theoriginalsetof Englishdata.The meanF1 andF2 values
and standarddeviationsfor theseEnglishdisyllabictokens
acrossEnglish and Spanishindicatesthe presenceof a
language-specific
factorin the phoneticrealizationof phonemic vowelcategories.
C..A comparison of two five-vowel systems
In order to test the independenceof this base-ofarticulationeffectfrom an effect of inventorysize, a comparisonof two phonemicallyequivalentfive-vowelsystems
was performed.For this comparison,the presentSpanish
data were comparedto data for Greek vowels taken from
Jongman
et al. (1989).In thatstudy,the auth.,9rs
recorded
fourmalenative
speakers
ofModem
Greek
p•bducing
four
repetitionsof wordsexemplifyingthe five phonemicvowel
contrastsof the language.In thesebisyllabicwords,the target vowelswere precededby a bilabial consonantand followed by an alveolar consonant,thus facilitatinga direct
comparisonwith the presentSpanishdata which used the
same consonantal
context.
The
words
were
embedded
in
frame sentences,and the vowel formant measurementswere
takenfrom LPC spectra,as describedin that paper.
A visualcomparison
of thevowelsin SpanishandGreek
(seeFig. 1) showsthatthevowelsof Spanish
aregenerally
higherin the F2 dimensionthan their Greek counterparts,
aregivenin TableI (EnglishCVCV). TheseEnglishCVCV
and, in the F1 dimension,there is a generaltrend for the
tokenswere thencomparedto the SpanishCVCV tokensto
Spanish
vowelsto havelower valuesthanthe Greekvowels.
seeif the systematic,
cross-language
F2 differencethatwas
(Spanish,
Greek)andvowel(/i/,/e/,
obtainedin thepreviousexperiment
persists
underconditions ANOVAswithlanguage
/a/,
/o/,
/u/)
as
factors
confirm
these
visualimpressions:
for
of similar
wordstructure.
3 Indeed,
ANOVAs
comparing
the
both
F1
and
F2
there
is
a
significant
main
effect
of
language
four sharedvowelsof Englishand Spanishin CVCV contextsshowthatthereis a significantmaineffectof language, [F(1,4)=5.565,
p=0.025 for F1, F(1,4)=9.913,
suchthatEnglishvowelsaregenerallyhigherin F2 thanthe p =0.0037 for F2]. Additionally,
in bothcasesthelanguage
SpanishvowelsIF(1,3) =8.483, p = 0.0086].Furthermore, X vowel interactionfails to reachsignificance
[F(1,4)
as in the previousexperiment,thismaineffectfails to reach
=0.264, p=0.899 for F1, F(1,4)=0.100,
p=0.9814 for
significancein the F1 dimensionIF(1,3) =1.232, F2].
p=0.2803]. Finally,the!anguageXvowel
interaction
is not
The generalresultof thiscomparison
of the Greekand
significant
for eitherF1 [F(1,3)=0.819, p=0.4984] or Spanishvowelsis that thesetwo phonemicallyequivalent
F2 [F(1,3)=0.361, p=0.7816]. Thusthesedataindicate
vowel systemsshow a systematicdifferenceregardingthe
acousticrealizationof the sharedvowel categories:
the vowels of Spanishare generallyhigherin F2, and lower in F1
thanthe corresponding
vowelsof Greek.Thuswe can concludethat a language-specific,
base-of-articulation
property
thelocationof vowel
thatis consistent
withthenotionof a language-specific
base- playsan importantrolein determining
of-articulation effect.
categories
in the acousticspace,andthatthispropertyfuncIn summary,
thecrucialpointin thiscomparison
of the tionsindependently
of the generalsize andstructure
of the
EnglishandSpanish
vowelsis thatall thevowelsof English vowel inventory.In particular,the presentdataindicatethat
are generallyhigherin F2 thantheir Spanishcounterparts. the phonemicallyequivalentvowelsof English,Greek, and
This systematicdifferencefor all of the sharedvowels of the
Spanishall differ systematicallywith respectto one another
two languages indicates a language-specificbase-of- in the F2 dimension. In the case of each of the four vowels
articulationeffect, ratherthanan expansioneffect due to the
commonto Greek, Spanish,and English,the Englishvowel
crowdedhess
of theEnglishvowelspacerelativeto the Spanis higherin F2 than the Spanishvowel, which is in turn
ish vowel space.Furthermore,
the observed
F2 difference
higherin F2 thanthe Greekvowel.Theseobservations
thus
cannotbe accountedfor by a differencein vocaltractlength
suggest
that,
with
respect
to
these
three
languages,
the
genbetweenthe two groupsof speakers,sincewe do not find
eral base-of-articulationfor English involves the most
similar shifts for all formants. Finally, an effect of word
frontedtongueposition,the Spanishbase-of-articulation
instructure can be discounted since the observed formant differencesacrossthe two languages
persistwhenword struc- volvesan intermediatetongueposition,and the Greekbaseture is controlled.Thus this comparisonof vowel locations of-articulationinvolvesthe leastfrontedtongueposition.
that the effect we found in the comparisonof the English
monosyllabic
wordsandthe Spanishdisyllabicwordscannot
be accountedfor by the differencein word structurealone.
Rather,theserestfitssuggestthat indeedthe Englishvowels
differ systematically
from the Spanishvowels,in a manner
1920 J. Acoust.Soc.Am., VoL97, No. 3, March1995
A. Bradlow:Comparativestudyof Englishand Spanishvowels 1920
TABLEII. Comparison
of the/i/-lel-lo/-/u/area in English,Spanish,
and
Greek.
Difference
EnglishCVC vs SpanishCVCV
EnglishCVC vs GreekCVCV
EnglishCVCV vs Spanish
CVCV
EnglishCVCV vs GreekCVCV
SpanishCVCV vs GreekCVCV
EnglishCVC vs EnglishCVCV
Greekvowel spaces,whereas,in the opensyllablecontext,
the threevowel spacescovercomparable
areas.
Difference
+18 832 Hz2
+23 749 Hz2
+2645 Hz2
+7562 Hz•
+4917 Hz•
+16 187 Hz•
+12.7%
+16.6%
+1.8%
+5.3%
+3.4%
+10.7%
E. Tightness of within-cal:egoryclustering
In orderto investigatethe effectof numberof phonologicalcategories
on tightness
of within-category
clustering,
the coefficients of variations for the F1 and F2 values of the
D. Expansion of the acoustic vowel space
I now turn to a comparison
of the range,or areain the
acousticvowel space,coveredby the vowel categoriesof
EnglishandSpanish.Basedon the dispersion
principle,we
expectthat the relativecrowdedhess
of the Englishvowel
inventorywill causean expansionof the English acoustic
vowelspacerelativeto the Spanishacousticvowelspace.In
the comparison
of the locationsof the Englishand Spanish
vowelsin theacoustic
spacewe sawthattheEnglishvowels
aresystematically
shiftedupwardin theF2 dimension
relativeto theSpanish
vowels.However,thisdifference
between
the two languagesregardingtheir bases-of-articulation
does
not precludean expansion
effect.In otherwords,it is possiblethattheEnglishvowelsarebothhigherin F2 andcover
a greaterareathanthe Spanishvowels.
In orderto comparethegeneralrangeof theEnglishand
Spanishvowels,the area coveredby the quadrilaterals
defined by the meanF1 and F2 valuesof the four common
vowelswas calculated
(TableII). For the Englishvowels,
both the CVCV
and the CVC
data were included in this
comparison.
As an additionalpointof comparison,
the correspondingareacoveredby the Greek/i/,/e/,/o/, and/u/was
includedin thisanalysis.
Figure1 showsthesequadrilaterals
in theF1 by F2 spacesof eachof the threelanguages.
Theresultsof thiscomparison
of the/i/-/e/-/o/-/u/area
in English,Spanish,and Greekshowthat the Englishacoustic vowel spaces,
for boththe CVCV andCVC data,cover
more area than either the Spanishor the Greek acoustic
vowel spaces.However,the magnitudeof the differencevaries depending
on the syllabiccontextof the Englishvowels.
The area coveredby English/i/-/e/-/o/-/u/ in the closed
syllablecontext(the CVC data)is 12.7% greaterthanthe
Spanisharea, and 16.6% greater than the Greek area,
whereasthe areacoveredby English/i/-/e/-/o/-/u/in the
opensyllablecontext(theCVCV data)is only1.8%greater
thantheSpanisharea,and5.3% greaterthantheGreekarea.
(The /i/-/e/-/ol-/u/ areasin Spanishand Greekdiffer by
3.4%.) Thusthe Englishclosedsyllablevowelspaceis expandedin the acousticdomainrelativeto the Spanishand
fourvowelscommonto Engl.
ishandSpanishwerecompared.
For thiscomparison
theEnglishCVC (closedsyllable)data
were comparedto the SpanishCVCV data.In addition,the
EnglishCVC (closedsyllable)data were comparedto the
EnglishCVCV (opensyllable)data.Bothof thesecomparisonsinvestigatetheeffectof manyversusfew categories:
the
formeris within Englishand acrosssyllabiccontexts;the
latteris acrosslanguages
usingsyllabiccontexts
thatcontrast
manyversusfew categories.
TableIII givestheresultsof this
comparison.
The presentdataalsop•ovidea meansfor testingtheoretical predictionsregardingdifferencesin clusteringbetweencategories
within eachlanguage.Specifically,
accord-
ing to QTS (Stevens,
1972, 1989)the pointvowels/i,a,u/
shouldshowlesswithin-category
variabilitysincetheyoccur
in quantalregionsof thearticulatory
vowelspace.However,
in a testof thisprediction,
Pisoni(1980)foundthatthestandarddeviations
of theEnglishpointvowelswerenot significantly smallerthan the standarddeviationsof the nonpoint
vowels.In accordance
with thatresult,basedon the present
data, we find that the F1 and F2 standard deviations of
English/i,a,u/are not significantlysmallerthan the F1 and
F2 standard
deviations
of theeightEnglishnonpointvowels.
(Forthiscomparison,
theEnglishCVC andCVCV datawere
pooled.
n)Similarly,
wefindnodifference
between
theF1
andF2 standarddeviationsfor the Spanishpointand nonpointvowels.The resultsof theseanalysesare summarized
in Table IV.
The resultsof thesecomparisons
indicatethat the tightnessof within-category
clustering
doesnotvary significantly
as a functionof the numberof phonological
categories.
The
F1 and F2 coefficientsof variationdo not differ significantlyacrossthe EnglishCVC dataandthe SpanishCVCV
data,nor do they differ within Englishacrosssyllabiccontexts.Furthermore,
we find r o differencebetweenthe point
vowelsandnonpointvowelswith regardto within-category
variation.Thus these data indicatethat the tightnessof
within-category
clusteringis notdependent
on the sizeof the
vowel inventory.
TABLE Ill. A comparison
of the F1 andF2 coefficients
of variationacrossEnglishCVC andSpanishCVCV
(/i,e,o,u/),andEnglishCVC andEnglishCVCV (all 11 phonetic
catggorics).
Eng.
1921
EnglishCVC vs SpanishCVCV
Span.
diff.
t(3)
p value CVC
F1
0.094
0.065
F2
0.089
0.094
0.029
-0.005
2.165
-2.02
J. Acoust.Soc. Am., Vol. 97, No. 3, March 1995
EnglishCVC vs EnglishCVCV
CVCV
diff.
t(10)
p value
0.0735
0.086
0.092
0.8468
0.092
0.087
-0.006
0.005
-0.•
0.782
0.6413
0.4523
A. Bradlow:Comparativestudy of [--nglishand Spanish vowels 1921
TABLE IV. A comparison
of theFI andF2 standard
deviations
for thepointvs nonpoint
vowelsin English
(CVC andCVCV data)andin Spanish.
pt.
non-pt.
English
diff.
t(20)
p value
pt.
non-pt.
F1
60
44
16
1.072
0.2964
26
31
F2
176
131
45
2.048
0.0539
126
111
IV. DISCUSSION
A. Base of articulation
Spanish
diff.
t(3)
5
-15
0.422
-0.522
p value
0.7014
0.6375
exhibitedby relatively high F1 valuesin the acousticdomain.
An implicationfor theoriesof vowel inventoriesof the
The generalgoal of this comparativeacousticstudyof
observedF2 differencebetweenEnglishandSpanishvowels
the Englishand Spanishvowelswas to explorethe effectof
is that, in order to assessthe effect of universalfactorson the
inventorysize on the acousticrealizationof the phonemic acoustic
realization
of vowels,sucha language-specific
propvowelcategories
of EnglishandSpanish.
The firstfindingof
erty mustbe takeninto account.Accordingly,this finding
thisstudyis thattheEnglishandSpanish
vowelspaces
differ contradictsthe predictionsof theoriesof vowel inventories
systematically
in the locationof theirvowelcategories
in the
that proposeconsistent
locationsin the acousticspacefor
acousticspacedefinedby F1 andF2. A comparison
of the
similar phonemicvowel categoriesacrossdifferent lanlocationsof the four vowelscommonto Englishand Span- guages.
For example,in assessing
theconformity
of acoustic
ish, namely/i/,/e/,/o/, and/u/, showsthatthe Englishvowdatato thepredictions
of DT, theabsolute
locationof vowel
els are all significantlyhigherin theF2 dimensionthantheir
categories
may not be an effectivemeasureof dispersion;
Spanishcounterparts,
suggesting
thattheEnglishvowelsare
rather,factorssuchas the areacoveredby thevowels,or the
all articulatedwith a frontedtonguepositionrelativeto the
relativearrangement
of thevowelsin theacoustic
space,may
Spanishvowels.
providemoreaccuratemeasures
of dispersion.
This finding is consistentwith other cross-language
comparisons
of acoustic
vowelspaces(e.g.,Disnet,1983),
B. Dispersion theory (DT)
whichfind that the vowelsof one languagemay differ in a
systematicway from similar vowels of anotherlanguage.
TheguidingprinciplebehindDT is thatvowelswill tend
Thiscross-linguistic
difference
hasbeenaccounted
for by the to be maximally,or sufficiently,dispersed
in the acoustic
notionof a language-specific
base-of-articulation
property, spacein orderto minimizethe potentialfor perceptualconwhichis an importantaspectof the description
of the sound fusionbetweenseparate
vowelcategories.
Withinthistheory
of the available
systemof a language,and serves,in part, to differentiate it usuallybeenassumedthat the boundaries
systematically
thegeneralphoneticqualityof two languages acousticspaceare defineduniversallyand that the distance
that may sharecertainphonemiccategories.
In otherwords, betweenthe separatevowel categorylocationsis a measure
vowel categoriesthat have the same phonologicalfeature of overalldispersion
(e.g.,Liljencrants
andLindblom,1972;
specifications
andthatoccupysimilarpositions
in theacous- Lindblom,1975, 1986).However,as demonstrated
by the
tic spaceacrosstwo differentlanguages
may havedifferent presentdataandothercross-linguistic
acoustic
studies(e.g.,
of the
precise phonetic realizationsdue to different bases-of- LindanandWood,1977;Disnet,1983),theboundaries
articulationof eachlanguage.
acousticvowel space are more accuratelydefinedon'a
As a possiblesourceof this language-specific
base-of- language-specific
basis.
articulation
property,Honikman(1964) proposes
that the
With regardto thegeneralprincipleof DT, the resultsof
base-of-articulation
of a languageis determinedby the arthe presentstudyprovidesomeindicationof a positivecorticulatorysettingof the mostfrequentsegments
andsegment relation between inventory size and area covered in the
combinations
of the language.For example,she proposes vowelspace;however,thiscorrelationis variabledepending
that the base-of-articulation
for BritishEnglishis the cardion the syllablecontextof the Englishvowels.In the closed
nal alveolartongueposition,suchas for/t,d,n,s,z/, sincethe
syllablecontexttheEnglish/i/-/e/-/o/-/u/quadrilateral coversmoreareathanthecorresponding
Spanishor Greekquadalveolarplaceof articulation
is themostfrequentin thelanguage.This explanation
is consistent
with the findingof the
rilaterals.However,in the opensyllablecontextthe English,
presentstudythatthe Englishvowelsgenerallyhavehigher Spanish,and Greek/i/-/e/-/o/-/u/ quadrilaterals
all cover
F2
values, and thus more fronted (that is, alveolarlike)
tonguepositions,than the corresponding
Spanishvowels.
However, since coronal segmentsoccur with a high fre-
quencyin many(orperhaps
most)languages,
a carefulstudy
of the acousticcharacteristics
of a languagewhosemostfrequentsegmentsare noncoronalis neededin orderto verify
this proposedsourceof the base-of-articulation
of a lan-
comparableareas.A possiblesourceof the difference in area
coveredby the Englishvowelsacrosssyllablecontextscould
be the distributionof Englishvowels in closedversusopen
syllables.Both tenseand lax vowels can occur in closed
syllables,but only tensevowelscan occurin opensyllables
(Ladefoged,
1993).Thatis, in theclosedsyllable,CVC context the Englishvowel spaceincludesmore categoriesthan
in the opensyllable,CVCV context.In fact, in opensyllables
guage.Forexample,
for languages
suchasArabicand
as Spanwhichhavea preponderance
of backsegments,
Honikman's Englishhasexactlythesamenumberof categories
ish and Greek in the/i/-/e/-/o/-/u/region of the acoustic
proposalpredictsa back base-of-articulation
that shouldbe
1922 J. Acoust.Soc. Am., Vol. 97, No. 3, March 1995
A. Bradlow:Comparativestudyof Englishand Spanishvowels 1922
vowel space.Thus it couldbe that the/i/-/e/-/o/-/u/areas
varybothwithinandacrosslanguages
according
to thenumberof phonological
categories
thatoccupythisregionof the
vowelspace.Alternatively,the differencein areacoveredby
the Englishvowelsin openandclosedsyllablescouldbe a
generalsyllableeffectthatoperatesindependently
of inventory size.
Anotherpossiblestrategyfor reducingthe potentialfor
intercategoryconfusionis to limit the degreeof withincategoryspread.Accordingto thisstrategywe wouldexpect
to find a positivecorrelationbetweeninventorysize and
tightness
of within-category
clustering.
However,thedataof
the presentstudydid not showsucha correlation;rather,the
datashowedno differencebetweenthe tightness
of withincategoryclusteringeitherwithin English(acrosssyllable
contexts),
or acrossEnglishandSpanish.
It is possible
that
this result is attributable to the limited environment in which
the vowelsof thesetwo languages
were examined.In other
words,it is possiblethata differencein thedegreeof withincategoryclusteringin Englishand Spanishwould emergein
a studythatsystematically
variedthesegmental
environment
in which the targetvowelsappear.
An exampleof sucha studyis Manuel(1990)who investigatedthe effect of inventorysize and structureon the
degreeof vowel-to-vowelcoarticulationin threeAfrican languages,Ndebele,Shona,andSotho.The resultsof thatstudy
showthatthe two languages
with five vowels,Ndebeleand
Shona,have greateranticipatorycoarticulation
for the low
vowel/a/than
does
thelanguage
withseven
vowels,
Sotho.
5
However, for the midvowels thesedata show no difference in
the degreeof vowel-to-vowelcoarticulationbetweenthe
five-andseven-vowel
systems.
It is possible,
however,thata
moreconsistent
differencewouldemergein a similarcomparisonof languages
suchas Englishand Spanish,which
have a larger differencein inventorysize. Such a result
wouldprovidea strongindicationthat limiting the degreeof
within-category
clusteringis an attestedmeansof ensuring
sufficientdispersion.
C. Quantal theory (QT)
In contrastto DT, which proposesthat the locationsof
vowel categories
in the acousticspaceare determinedby a
principleof sufficientdispersion
andarethussomewhat
variable acrosslanguages,QT proposesthat there are acoustically stableregionsthatoperateuniversally.
Thusaccording
to QT, therearecertainvowels,specifically
thepointvowels,
whose locationsin the acousticspaceshouldbe constant
acrossall languages.
However,the findingthat the second
formantfrequencyof theEnglishhighfrontvowelis significanfly differentfrom that of the Spanishhigh front vowel
disconfirms
theprediction
of QT thatthehighfront(thatis,
the low F1 andhighF2) cornerof the acoustic
spaceis a
strictlyquantalregionthatrepresents
a stablephonemiccategoryacrosslanguages.
Rather,thepresentdataindicatethat,
within this cornerof the acousticspace,there is a certain
degreeof flexibility regardingthe preciselocation of the/i/
categoryacrossdifferentlanguages.Thus, in order to maintain the generalprincipleof QT, at leastas it pertainsto the
locationof vowelsin the acousticspace,we would have to
1923 J. Acoust.Soc. Am., Vol. 97, No. 3, Mamh 1995
positrelativelystableregionsasopposed
to absolutely
stable
regions.Furthermore,in accordance
with the resultsof a
studyby Pisoni(1980), the presentdatado not showany
clearpatternof lessvariabilityfor the pointvowelsas opposedto the nonpointvowels.In otherwords,the present
data do not supportthe claim that there are certainstable
regionsof the acousticvowel space.Rather,the datashow
considerable
variabilityacrossthe two languages
regarding
the locationsin the acousticspaceof all of the sharedvowel
categories.
In conclusion,the resultsof this comparisonof English
andSpanishvowelssuggest
thatthelocationin theacoustic
vowel spaceof the vowel categories
is determined,in part,
by a language-specific,
base-of-articulation
property.In addition, the data suggestthat syllable structure,rather than
overallinventorysize,determines
thedegreeof expansion
of
the acousticvowel space.Finally,the data showthat the
tightness
of within-category
clustering
doesnotdifferfor the
languagewith a crowdedvo•velspaceandthe languagewith
an uncrowdedvowel space.
ACKNOWLEDGMENTS
This work appearedas Chap. 2 in my 1993 doctoral
dissertation.
I gratefullyacknowledge
the manyhelpfulcommentsof Allard Jongman,Abigail Cobh, John Kingston,
Carol Krumhansl,JoanSereno,Marios Fourakis,Kevin Munhall, and Linda Polka. For technical assistancein the Cornell PhoneticsLaboratory,I thank Scott Gargashand Luke
Karen.This workwassupported
in partby a Grant-in-Aidof
Researchfrom SigmaXi, The ScientificResearchSociety.
1However,
sceMendez
(1982)fora contradicting
result.
2Acomparison
of theformant
valuesfor boththeEnglish
andSpanish
vowelsin thisstudywith thosefrompreviousstudiesshowsthatthepresent
measurements
aresimilartootherdatareported
in theliterature
(e.g.,Petersonand Barney,1952; Delanre, 1969; Mendez, 1982).
3Acomparison
of theFI andF2 measurements
fromthedi-andmonosyllabic Englishtokensshowsthat the locationsof the targetvowelsin the
acousticspaceare affectedby the syllabicstructureof the word in which
they appear.Specifically,the F2 fn:quencyin the CVC conditionis higher
than in the CVCV condition[F(1.,10)=7.õ71, p=0.0076 by a twofactorANOVA with CV pattern(CVC, CVCV) andvowel(the11 English
vowels)as factors].Thusit appea•sthata syllable-final/t/raises
theF2
frequencyof thepreceding
vowel •elativeto theF2 frequencyin an open
syllable.Nevertheless,
therelevantcomparison
for thisstudyis betweenthe
Englishand SpanishCVCV tokens.
*Two-factor
ANOVAs
withvowel(l:oint
versus
nonpoint)
andsyllable
type
(CVC vs CVCV) asfactors,andF I andF2 as dependent
variables,
yield
no significanlmain effeclsor interactions.
SNote
thata recent
acouqtic
andphonological
study
ofSotho
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