Perceptionof the voiced-voicelesscontrastin syllable-finalstops
James Hillenbrand
Department
ofCommunicative
Disorders,
2299Sheridan
Road,Northwestern
University,
Evanston,
Illinois
60201
DennisR. Ingrisano
Speech
Research
Laboratory,
Department
ofCommunicative
Disorders
andSciences,
Wichita
State
University,
Wichita;Kansas67208
Bruce k. Smith
Department
ofCommunicative
Disorders,
2299Sheridan
Road,Northwestern
University,
Evanston,
Illinois
60201
James E. Fiego
Department
ofBiocommunication,
U•4BMedicalCenter,University
Station,
Birmingham,
•41abama
35294
(Received
9 June1983;accepted
for publication
6 February1984)
A computer
editingtechnique
wasusedto removevaryingamounts
of voicingfromthesyllablefinalclosureintervalsof naturallyproducedtokensof/pcb, pod,p•g, pag,pig,pug/. Vowelsfor
all sixsyllables
wereapproximately
thesameduration,andthefinalrelease
burstswereretained.
Identificationresultsshowedthat voiceless
responses
tendedto occurin relativelylargenumbers
whenall of theclosurevoicingand,in mostcases,
a portionof thepreceding
vowel-to-consonant
(VC}transition
hadbeenremoved.
A second
experiment
demonstrated
thatremoval
offinal
release
burstshadverylittleeffectontheidentification
functions.
Acousticmeasurements
were
madeinanattempt
togaininformation
abouttheacoustic
bases
ofthelisteners'
voiced-voiceless
judgments.
In general,
stimulithatsubjects
tended
to identifyasvoiceless
showed
higherfirstformantoffsetfrequencies
andshorterintensitydecaytimesthanstimulithatsubjects
tendedto
identifyasvoiced.However,for stopsfollowing/i/and/u/these acoustic
differences
were
relativelysmall.We wereunableto finda singleacoustic
measure,
or anycombination
of
measures,
that clearlyexplainedthelisteners'voiced-voiceless
decisions.
PACS numbers: 43.70.Dn, 43.70.Ve
INTRODUCTION
The voicingcontrastin Englishstopshasbeenstudied
ratherextensively,
but the majorityof thiswork hasfocused
on stopsin initial position.The most well-developed
approachto describing
voicingcontrasts
in initialstopsis the
glottal/supraglottal
timing view proposedby Lisker and
Abramson
(1964,1967,1970;seeMal6cot,1970,foranalternativepoint of view).Articulatorycontrolof initial stop
voicingcontrasts
isthoughtto involvevariations
in thetimingofvoicingonsetrelativetoarticulatory
release.
Thevoießing opposition
in finalstopsalsoinvolvesthe timingof a
laryngealgesturerelativeto articulatoryeventsin theupper
airway. For syllablesendingin voiceless
stops,a laryngeal
gesturetypicallyterminatesvoicingat aboutthe sametime
that articulatoryclosureis achieved.For syllablesendingin
voiced stops,glottal vibration generallycontinuesinto at
leastsomeportionof theclosureinterval.In thissense,
syllable-finalvoicingcontrasts
mightbethoughtof in termsof a
"voiceoffsettime" featuresomewhatanalogousto voiceonsettime in initial stops.
In articulatoryterms,voiceoffsettime would refer to
thetimingof a phonation-terminating
gesturerelativeto the
achievementofarticulatoryclosure.Becauseof theearlyterminationof glottal vibrationin final voicelessstops,these
syllablesare generallycharacterized
by (1) relativelyhigh
firstformant(F 1)terminatingfrequencies
(Wolf, 1978)and
18
J. Acoust.Sec.Am.76 (1), July1984
(2) silentrather thanßpartially or fully voicedclosureintervals (Smith, 1979;Hogan and Roszypal,1980;Flege and
Brown, 1982). Further, measurementsthat were made as
pilot work to the presentstudyshowthat vowelswhichprecedevoiceless
stopsare generallyterminatedwith a more
abruptdropin intensityascomparedto vowelsthat precede
voicedstops(seeDerbock,1977,for similarfindingsonstops
in FrenchandDutch).The kindof laryngealtimingdistinction discussedabove,however,doesnot accountfor the well-
known influenceof consonantvoicingon the duration of
preceding
vowels.In phrase-final
positionin English,vowels
precedingvoicedconsonantsare generallyabout 50 to 100
ms longerthan vowelsprecedingvoiceless
consonants(e.g.,
House and Fairbanks, 1953; House, 1961; Petersonand Le-
histe,1960;Chen,1970)?
On the basisof the acousticpropertiesassociatedwith
the syllable-finalvoicing contrast, perceptual cues to this
distinctionmight involvethreekindsof acousticfeatures:(1)
thepresenceversusabsenceof a low-amplitudelow-frequen-
cy "voicebar" duringtheclosureinterval,(2)somecombination of frequencyand intensitycharacteristicsassociated
with gradual versusabrupt terminationof the preceding
vowel(i.e.,F 1offsetfrequencyandintensitydecaytime),and
(3)thedurationofthepreceding
vowel.Althoughthevowel
durationdifferenceis oftenconsideredto be of primary perceptualimportanceto finalstopcognateoppositions,
experi-
0001-4966/84/070018-09500.80
¸ 1984Acoustical
Societyof America
18
mental
evidence
supporting
thisconclusion
consists
primarIn thepresent
studyvoicing
cueswereexamined
using
ilyofa series
ofsynthetic
speech
studies
byRaphael
andhis syllable-final
voicedstopsvaryingin placeof articulation
colleagues
{Raphael,
1972;
Raphael
etal.,1975,1980).
2Ra- andvowelenvironment.
Editingtechniques
wereusedtodephael(1972)
used
thePattern
Playback
tosynthesize
sylla- terminehowmuchof the finalvoicedsegment
hadto be
blesendingin voiced
andvoiceless
stopsandfriesrives.
In
general,
finalconsonants
wereheardasvoiceless
whenpreceded
byvowels
ofshortduration
andasvoiced
whenprecededby vowelsof longduration.Raphaelconcluded
that
preceding
voweldurationwasbotha necessary
andsufficientcueto syllable-final
voicing.
Similarfindings
werereported
intwosubsequent
synthesis
studies
byRaphael
etal.
(1975,1980).
Theconclusions
based
onthese
synthesis
studies
have
notbeensupported
by morerecentworkinvolving
edited
natural speech.For example,Wardrip-Fruin(1982a)
showed
thatvowels
preceding
finalvoicedstopscouldbe
reduced
in duration
byone-third
withoutelicitingvoiceless
responses.
Severalotherinvestigators
usingeditednatural
speech
haveshownthatreducing
vowelduration,
by itself,
doesnottypically
makea naturally
produced
voicedstop
sound
voiceless
(O'Kane,1978;HoganandRozsypal,
1980;
Raphael,
1981;Revoile
eta!., 1982).It hasalsobeenshown
thatexpanding
vowel
durations
ofnaturally
produced
sylla-
removedbeforesubjects
heardfinal voiceless
stops.The
studyinvolved
twolistening
experiments
anda series
ofpost
hocacousticanalyses
of the editedstimuli.The stimulifor
experiment1 wereeditedin sucha wayasto retainthefinal
releasebursts.Experiment2 examinedthe role of release
burstsby askingsubjects
to identifyeditedstimulibothwith
andwithoutfinalbursts.The purposeof the acoustic
measurements
wasto providepreliminarytestsof severalhypotheses
regarding
acoustic
cuesto finalvoicingcontrasts.
I. EXPERIMENT
1
A. Stimuli
1.Record/ngand measurement
Thestimuliconsisted
ofa combination
ofnaturallyproducedandeditedtokens
of/p•b, p•d,p•g,pug,pig,pug,p•p,
pet, p•k, pak, pik, puk/. A maletalkerproducedseveral
repetitions
ofeachsyllable.
Audiorecordings
weremadeina
sound-treated
boothwith a headsetmicrophone
(Shure
SMll) anda reel-to-reel
tapedeck(AkaiGX --4(X}0DB).
stimuliwerethenlow-pass
filteredat 4
blesending
invoiceless
stops
does
notresultin voiced
stop The tape-recorded
kHz
and
digitized
at
a
10-kHz
sample
frequency.
Oscillograjudgments(Hoganand Rozsypal,1980;Revoileet al.,
phicrepresentations
of 100-mssegments
of thestimuliwere
1982).
3
ona high-resolution
graphics
terminal(Tektronix
Mostoftheevidence
fromeditednaturalspeech
studies displayed
4010).
The
oscillograms
were
used
to
segment
eachstimulus
suggests
thatfinalstopvoicingcontrasts
arecuedprimarily
into
(1)
voice
onset
time
(VOT)
of
initial/p/,
(2)vowel,(3)
by acoustic
information
in the vicinityof articulatory
clofinal
stop
closure,
and
(4)
final
stop
release
burst.
n For the
sure.For example,Wolf (1978)madeeditingcutsat several
stimuliendingin voicedstops,thesemeasurements
were
locations
from naturallyproducedsyllables
suchas/•eb/,
used
to
select
which
of
the
multiple
repetitions
would
be
/•-cl/, and/a•g/.Removal
oftheentireclosure
intervalproused
in
the
perception
tasks.
Tokens
were
required
to
meet
duced16%voiceless
responses,
whileremovalof theclosure
closure
intervalmeasuring
intervaland threepitchperiodsfrom the vowel-to-conso- twocriteria:(1)a fullyvoiced
about
75
ms
(
_
5ms)
and
(2)
an
audible
finalburstmeasurnantIVC) transitionproduced
70% voiceless
responses
(see
ing
5-15
ms
in
duration.
Measurements
of the six stimuli
Revoileetal., 1982,for similarfindings).
Theseresultsseem
ending
in
voiced
stops
are
shown
in
Table
I.
For comparison
tosuggest
thatfinalstopvoicingcontrasts
arecuedprimarily
the
table
also
gives
duration
measurements
from
thesixsylby differences
in thewayin whichthepreceding
vowelis
lables
ending
in
voiceless
stops.
These
stimuli
were
included
terminated
{Parker,1974;WalshandParker,198I).
as
a
reliability
check
on
listener
responses
and
were
notreThepresentstudywasdesigned
to examinecuesto the
quired
to
meet
any
durational
criteria.
perception
of finalstopvoicingin greaterdetailby usinga
fine-grained
editingtechnique
on naturallyproduced
sylla- /TABLEI. Timemeasurements
(inms)for(1)VOToftheinitial
stop,
(2)
duration
ofthefinalstop,(4)burstduration,
and
ble-finalstopsin several
vowelenvironments.
Wolf (1978) vowelduration,(3)closure
duration.
Thevalues
in parenth
eses
indicate
thevoweland
andRevoileet al. (1982)studiedcuesto finalstopvoicing {5}totalsyllable
syllable
durations
afterapplication
oftheeditingtechnique
thatequali7ed
usingstimuliin theenvironment
of/•e/, a vowelthatmight voweldurations
forstimuliendingin voicedstop•.
tendto accentuate
differences
in bothF 1 offsetfrequency
anddecaytime.Theopenvocaltractconfiguration
of vowels
VOT
Vowel
Closure Burst
Syllable
suchas/•e/results in relativelyhigh intensities
and highfrequencyfirstformants.As the vocaltract constrictsfor the
finalclosure,substantialdecreases
are seenin overallintensi-
p•b
ped
peg
pag
ty andin thefrequency
of thefirstformant.Therefore,editingcutsthattruncatetheVC transitionwouldresultin rela- pig
pug
tivelyhighF 1 offsetfrequencies
andshortdecaytimes.On
pep
theotherhand,moreconstricted
vowelswouldbeexpected pet
to showlessdramaticintensityandfrequency
changes
in the pœk
VC transition.For thisreasonit is unclearwhetherthepat- pak
tern of results obtained with/•e/would
also be seen when
editingcutsare made from stimuli in the contextof more
constrictedvowels, such as/i/and/u/..
19
J. Acoust.
Soc.Am.,Vol.76, No.1, July1984
pik
puk
37
47
67
61
122 (112)
131 (110)
106 (106)
174 (107)
77
71
76
73
7
4
8
16
243 (232)
253 (232)
257 (257)
324 (257)
49
65
149(113)
142(108)
73
75
13
5
284 (248)
288 (254)
30
58
82 '
111
105
116
41
95
51
88
86
85
...a
90
..."
11
93
4
108
88
94
18
23
12
140
270
243
337
248
279
"Tiffs token was uareleased.
Hillenbrand etal.: Voiced-voiceless contrast
19
2. Control of vowel duration
TOhold
anypotential
influence
ofvowel
duration
constantacrossthe six continua,a computereditingprocedure
was usedto modify the vowel durationsof the six stimuli
endingin voicedstops.Beginning
withthethirdpitchperiod
of thevowel,everyotherpitchperiodwasremoveduntil the
vowelwaswithin one-halfpitchperiodof 110ms.To avoid
introducing
clicks,editingcutsweremadeat zerocrossings.
By removingeveryotherpitchperiod,abruptdiscontinuities
in fundamentalfrequencyand formant frequencieswere
avoided.Sincethe editingprogramwasableto shortenbut
notlengthenvowels,all of thestimuliwereadjusted'to
accoroodatetheshortest
vowel.The vowelin/peg/was theshortestat 106msand wasleft unmodified.
Vowel and syllable
durationsafter applicationof this editingtechniqueare
shownin parenthese•
in TableI.
3. Edit?}gof closurevoicing
Varyingamountsofglottal pulsingwereremovedfrom
the closureintervalsof the six syllablesendingin voiced
stops.Figure I showsa continuumbasedon the natural to-
FIG. 2. Oscillogram
of the 20-msstimulusfrom the/peg/continuum
shownwiththeassociated
weighting
function.Starting35 mspriorto the
finalburst,theweighting
function
decays
linearlyover15msfroma gainof
onetoagainofzero,remains
atzerofor20ms,thenreturnsinstantaneously
to a gainof onefor the durationof the burst.Note that the nominalvalueof
20msrefersonlytotheamountoftimethattheweighting
function
remains
at zero.
kenof/peg/. Thecontinuum
consisted
of 13stimuliranging
from 0-120 ms of signalremoved,in 10-mssteps.Because
theclosure
intervalfortheoriginal/peg/was76 msin duration(seeTableI}, thestimulifrom80to 120msin thecontinuuminvolvethe removalof all of the voicingfrom the closureintervalanda portionofthepreceding
vowel.Editingof
the stimuliwas accomplished
by multiplyingthe original
digitizedwaveforms
by a seriesof weightingfunctionsof the
typeshownin Fig. 2. This figuredisplaysa weightingfunctionsuperimposed
onthestimulusfromthe/peg/seriesthat
is labeled"20" in Fig. 1. Valuesin the weightingfunction
rangedfrom zero(completeattenuationof the signal}to one
{nosignalattenuation).
The nominalvalueof 20 msrefersto
theamountof timethat the weightingfunctionremainedat
zero.The zero-amplitudeintervalwasprecededby a 15-ms
linear decay function which was intendedto simulatethe
gradualamplitudereductionthat generallyoccursin natural
speechwhen voicingterminatesprior to release.The decay
functionalso reducedthe possibilitythat the editing cuts
would introduce transients into the stimuli. It should be em-
phasizedthat the 20-msnominalvaluerefersonly to the
zero-amplitude
portionof the weightingfunctionand does
notincludethatportionof thesignalattenuated
bythe 15-ms
decayfunction.Followingthe zero-amplitude
interval,the
weightingfunctionreturnedinstantaneously
to a valueof
onein orderto retain.thereleaseburst.A seriesof weighting
functionswas calculatedindividually for each stimulusso
that this final full-amplitudeportion of the weightingfunction exactlyfit the releaseburst.
B. Subjects and procedures
Subjectswere 23 NorthwesternUniversity students
withnoreportedhistoryof hearingor speech
problems.
Presentationof stimuliand collectionof subjects'responses
wereunderthecontrolof a laboratorycomputerequipped
with a high-speeddisk drive and a 12-bit D/A converter.At
theoutputof theD/A converter
thestimuliwerelow-pass
filteredat 4 kHz, amplified,attenuated,and deliveredbinaurallyovermatchedTDH-49 headphones.
The outputattenuatorwasadjustedsothat signalspeakedat 78 dBA.
Each stimulus continuum consisted of 14 tokens: one
numbersto therightof eachoscillogram
arenominalvaluesthatreflectthe
exemplarof the naturalvoicedstop,12editedversions,
and
onenaturalproductionof thevoiceless
cognate.
The identificationtestsconsisted
of tenrandomlyorderedpresentations
ofthe 14stimuli.Oneachtrialsubjects
wereaskedto pressa
amountof signalthatwasremoved
bytheeditingprocedure
(seetextj.
button labeledB,D,G or a button labeledP,T,K. Each sub-
FIG. 1.Stimulus
continuum
constructed
bymaking
increasingly
largeeditingcutsformthevoiced
closure
intervalofa naturallyproduced/peg/.
The
20
d. Acoust.Soc.Am.,Vol.76, No.1, July1984
Hillenbrand
etal.: Voiced-voiceless
contrast
20
TABLE II. Mean voiced-voiceless
categoryboundaries,
standarddevia-
tions,andranges
foreachstimulus
continuum.
Thevalues
(inms)represent
the amountof signalremovedfrom the finalvoicedsegments
of syllables
endingin voicedstops.
Standard
981
9(!
• 881
89
>o7e
76
Continuum
Mean
deviation
Range
•
/peb/
/peal/
/peg/
68
77
77
iI
14
13
48- 88
58- 93
62-122
• 49
49
/pag/
/pig/
/pug/
70
61
63
7
6
7
$5- 80
54- 80
5O- 78
c•
3el
• •'e
39
28
88
18
ject wastestedon all sixcontinuaand eachreceiveda different orderingof the conditions.
C. Results
and discussion
•
3el
4el
59
VOICING
88
76
89
•
lei8
Ilei
l:2(!
N
REI'K•VEO
FIG. 4. Id•tification r•ul• shag
ronm•t. •ch f•cfion repr•U •
"N" • the a•s•
repr•n• r•
the eff•t of v•ng the vowel••1•
r•u!• fr• 23 •e•.
•e
• the un•i•
voi•l• sto•.
Table II showsvoiced-voiceless
categoryboundaries
andmeasures
Ofdispersion
foreachcontinuum.
Category
boundaries
were calculatedby linear interpolationof the
50% crossover
fromvoicedto voiceless.
In general,category
boundaries
tendedto occurin the 60- to 80-msrange.Figures3 and 4 showthe percentage
of voicedresponses
as a
functionof the sizeof the editingcut. Figure 3 showsthat
therewasa slightlyearliercrossover
for the labialcontin-
uumascompared
to thealveolar
andvelarcontinua.
Figure
4 showsearliercrossovers
for/pig/and/pug/, thetwovowelswith low-frequency
first formants.Althoughthe place
andvoweleffectsseemto befairly smallin termsof absolute
magnitude,two separaterepeatedmeasuresANOVAs
showed that both effects'were significant [place:
F(2,44)= 4.9,p < 0.05;vowel:F(3,66)= 20.2,p < 0.01].
In general,the listeningtestsshowedthat voiceless
responses
werenot elicitedin largenumbersuntil the closure
intervaland, in mostcases,a portionof the VC transition
had beenremoved.This findingis consistentwith the idea
Ilala=
OUP
DATA
CN-23)
leila
that informationin the VC transitionsis importantto the
perception
of finalvoicingcontrast.
A moredetaileddiscussionof thesefindingswill await the resultsof a seriesof
acousticanalysesof the stimuli,describedin See.III.
II. EXPERIMENT 2
The main findingof experimentI wasthat voiceless
responses
didnotpredominate
untilrelatively
largeamounts
of voicinghadbeenremovedfromthestimuli.The possibility exists,however,thatthesyllable-final
releaseburstscontainedcueswhichbiasedsubjectstowardvoicedresponses.
Thispossibility
motivateda second
experiment
with a new
groupof 11 subjectswhich examinedthe role of release
bursts. The stimuli for this experimentconsistedof the
/peb/,/ped/, and/peg/continuafromexperiment1.Stimuli fromeachcontinuumwerepresented
to thesubjects
both
with and without releasebursts. The releasebursts were eli-
minated
simplybyaligning
a cursortoredefine
theendofthe
stimulus.Subject-selection
criteria,instrumentation,
and
procedures
wereidenticalto thosedescribed
for experiment
1.
A. Results and discussion
• 78
7el
• se
se
•• 40
•• •i
•- PED
PEa
m-
•3a
• 20
4e
Theresultsfromexperiment
2 areshownseparately
for
eachplaceof articulationin Fig. 5. Althoughtheburstconditionsshowearliercrossovers
in eachcomparison,
thedifferences
in thecategoryboundaries
areonly 3-4 ms.A twowayrepeated
measures
analysis
of variancefelljustshortof
significance
for the burstversusno burstcomparison
IF
(1,10}= 4.6,p <0.07]. In contrastto the resultsof experi-
3e
29
ment 1, phoneticboundaries
werenot significantly
affected
bydifferences
in placeof articulationIF (2,20)= 3.0,p NS].
The place-by-burst
interactiondid not approachsignifiThe relativelyminor role playedby burstsin this experi-
•G. 3. Id•tion
r•ul• •o•ng •e •t
ofv•ing thep• ofpr•
ducfi• • the•
s•p. •h fun•
r•r•n•
the•1•
•ul•
23•e•.
•e "N" onthea•i•
repr•
r•
to theunMi•
voi•l•
21
sty.
d.Acoust.
Soc.Am.,Vol.76, NO.1, July1984
mentshouldbeinterpreted
in lightof thefactthattherelease
burstswere relativelybrief (15 ms or less}.Longerrelease
burstsforvoicedstopssometimes
showevidence
ofperiodicity (e.g.,Wolf, 1978}andmight,therefore,
influence
voicing
Hillenbrand
eta/.: Voiced-voiceless
contrast
21
--
not stronglyinfluencevoicingjudgmentsis supported
by
severalotherstudies(Mal6cot,1958;Wolf, 1978;Raphael,
1981;Wardrip-Fruin,1982a;Revoileet al., 1982).Thisresultisalsosensible
in lightofproduction
datashowing
thata
largeproportion
of finalstopsareproduced
withoutrelease
bursts(Rositzke,1943;CrystalandHouse,1982).
The minimalimportanceof finalburstswould'seemto
GROUPDATA CN-I I)
9B
8B
6•
implythattheduration
of theclosure
intervalwasnota
S0
\\
40
strongvoicingcue for thesestimuli.Sincethe final release
burstmarkstheendof theclosureinterval,it seemslogicalto
ß= PEB: BURST
assume that removal of this marker would alter the listeners'
3•
impression
of the durationof the interval.Therefore,the
failure to find large differences
betweenthe burst and no
burstconditions
suggests
that closuredurationdidnot playa
significant
role in the subjects'
voicingjudgments.This is
consistent
with Raphael(1981}who showedthat extending
final/g/closures to durationsappropriatefor/k/did not
elicit/k/responsesfrom listeners.
;0
98
IlL ACOUSTIC
Oneof thedi•cultiesin interpretingthelabelingresults
isthatcategory
boundaries
occurred
verycloseto thebeginningof theclosure
interval.Locationof theboundary
in this
regionmakes
it difficultto decide
between
twoverydifferent
(andpossiblynonmutuallyexclusive)
alternativesconcerningcuesto syllable-final
voicing.Onepossibility
isthatsubjeers'decisions
werebasedonthepresence
versus
absence
of
audiblevoicingduringthe closureintervals.Anotherpossibility is that decisions
werebasedon gradualversusabrupt
78
ß = PED= BURST
•
38
IBB
ANALYSIS
termination of the precedingvowels.Our strategyin this
sectionwas to try to make somespeculationsabout the
acousticbasesof our listeners'voiced-voiceless
judgments
basedon acousticanalysisof the stimuli.In particular,we
-
triedto findsystematic
acoustic
differences
betweenstimuli
that straddledthe voiced-voiceless
boundary.Threeparameterswereexamined:(1) presence
versusabsence
of closure
voicing,(2)the offsetfrequencyof the firstformant,and (3)
rate of intensitydecayat stimulusoffset.For all of these
analyses,
wecompared
measurements
fromthemostedited
stimulus
thatproduced
75%ormorevoiced
responses
with
80
$0
4B
ß-
theleasteditedstimulus
thatproduced
75% or morevoicelessresponses.
Since
these
represent
themostphysically
similar stimulithatproduced
qualitatively
different
labeling
re-
PEG: BURST
3B. n•P•T
sponses,
wereasoned
thatcomparing
measurements
from
thesepairsmightrevealacoustic
differences
thatlisteners
20
usedto make voiced-voiceless
judgments.
0
ß
0
10
29
30
40
$0
VOTCTNG
60
70
89
go I•N} 110 120
N
REHOVED
FIG.5. Identificationresultsshowingthe effectof removingthe release
burst.Eachfunctionrepresents
the pooledresultsfrom 11 listeners.The
"N" on theabcissa
represents
responses
to theuneditedvoiceless
stops.
Thefirstpossibility
thatwasconsidered
wasthatlisteners'judgments
mightberelatedto thepresence
versus
absenceof closurevoicing.Closurevoicingcanbe measured
eitherfromtime-or frequency-domain
representations.
Ona
spectrogram,
thedisappearance
of formants
aboveF 1 is
typicallyusedto markthestartof theclosure
inteval(e.g.,
Peterson
and Lehiste,1960)?If a closureintervalis unvoiced,
F 1andthehigherformants
will generally
terminate
thesame
time.Thisissimply
another
way
judgments.
There
issis
øevidence
thattheremoval
offinal atapproximately
releaseburstsfrom voiceless
stopshas a greatereffecton
ofsaying
thatthefirstformant
or"voice
bar"isnotusually
voicingjudgments
than the removalof burstsfrom final
evidentduringtheclosure
intervalforunvoiced
stops.However,if a closureintervalis voiced,a low-intensity,low-frequencyfirstformantor "voicebar"will usuallyextendbe-
voicedstops(Ma16cot,1958;Revoileet al., 1982).However,
thegeneral
conclusion
thatfinalbursts
fromvoiced
stops
do
22
J. Acoust.Soc. Am., Vol. 76, No. 1, July 1984
HJllenbrand
etal.:Voiced-voiceless
contrast
22
yondthetermination
ofthehigher
formants.
Forthepresent
studyclosure
voicing
wasdefined
astheintervalbetween
the
offsetof the secondformant and the offsetof the first for-
mant.This spectrum-based
measurement
technique
was
preferredto a time-domain
methodbecause
it allowedusto
evaluate
thepossibil/ty
thatth• resolution
oftemporalorder
mightbeinvolvedin theperception
offinalstopvoicingcontrasts.For example,it ispossible
that a finalstopwill tendto
soundvoiced//'theterminationoff I isdelayedby a significant amountrelativeto the offsetof the upperformants.
Conversely,
a finalstopmightsoundunvoiced
ifF l andthe
higherformantsterminateat aboutthe sametime. If th/s
hypothesis
iscorrect,thenstimulithat listenerstendto hear
asvoicedshouldshowasynchronous
offsets{i.e.,the terminationoff I isdelayedrelativeto theupperformants}
while
stimuli that listeners tend to hear as unvoiced should show
synchronous
offsets{i.e.,F l andthehigherformantsternflhateat roughlythe sametime}.
Measurements were based on extraction of formant fre-
quency,amplitude,
andbandwidthbylinearpredictivecoding {LPC)analysis(Markeland Gray, 1976}.Theseparameters were extracted every 6.4 ms over 20-ms
Hamming-windowed
segments.
The digital spectrograms
producedwith thistechniquewereusedto measuretheoffset
TABLE 111.Acousticmeasurements
fromstimulionopposite
sidesof the
voiced-voiceless
boundary
forthesixcontinua.
Thefirstcolumngivesthe
percentage
ofvoicedresponses
thatweree/icitedbythestimulua.
Thevalues
/n parentheses
areestimated
difference
limensfor decaytime(seetext).
St/mulus labels indicate the continuum from which the token was drawn
and thesizeof the editingcut. For all of the analyses,
comparisons
were
made between the mo•t edited stimulus that was heard as voiced at least
75% of the time and the least edited sthnulus that was heard as voicelessat
least 75% of the t/me.
Percent
Stimulus
voiced
responses
F 1
Closure
voicing
offset
frequency
Decay
time
p•50
p•b80
93
25
26
0
226
395
48 (16}
20
l•d60
pr.d90
83
21
6
0
227
485
34 (13)
16
p•g60
p•g90
' 89
14
0
0
3O5
486
29 (12}
16
pag60
87
0
334
49 (16)
pag80
10
0
410
27
pig50
90
0
232
59 (18)
pig70
20
o
249
4O
pug50 '
pug70
82
23
13
0
159
182
73 (21}
54
time of the first formant relative to the offset time of the
secondformant.This canbe thoughtof eitherasa measure,
ment of the amountof voicingpresentduring the closure
interval or as a measurement of relative offset time. The deci-
sionregardingthe terminationof a formantwasbasedon a
combinationof an increasein formantbandwidth,a decrease
in formantlevel,andthepresence
of abruptdiscontinuities
withpreviously
extractedformantfrequencies.
(}rosserrors
in formantextractionwereavoidedby checkingthe LPC
derivedmeasurements
againstconventionalspectrograms
(Kay Sonagraph,
model6061B}.
F 1offsetfrequency
wouldbeexpected
regardless
ofthelocationof theeditingcuts.Althoughtheappropriate
psychophysicaldata are not available,it seemsunlikelythat F 1
offset
differences
of 17and23Hz couldberesponsible
forthe
largedifferences
in labeling
responses.
?
The last parameterconsideredwas intensitydecay
time.A computer
programwasusedto measure
overallrms
intensityevery6.4 msover20-mstimewindows.Following
the procedurerecommended
by van den Broeckeand van
The results of these measurements are shown in Table
Heuven{1983},amplitudedecaytime wasexpressed
as the
III. 6Theresults
donotsupport
the'idea
thatsubjects'
voic- time neededfor signalintensity,expressedin decibels,to
ingdecisions
werebasedprimarilyon relativeoffsettimeor,
drop from 90% of its peakvalueto 10% of its peakvalue.
stateddifferently,on the presence
versusabsence
of closure
TableIII showsamplitudedecaytimesfor stimulion oppovoicing.In mostcases
F 1andF 2 terminhted
simultaneously sitesidesof the voicingboundaryfor the sixcontinua.In all
for stimuli on both sidesof the voiced-voicelessboundary.
casesthe stimulusthat subjects
tendedto hearasvoiceless
Pastore(1983)hasshownthat thedifference
limenfor offset
showed
a moreabruptdropin intensity.
On theaverage,
the
asynchronies
isabout7 msfor nonspeech
stimuli300msin
decaytimesfor stimulion the voicedsideof the boundary
duration.
ff thisisa reasonable
estimate
forspeech
sounds, wereabout 1.7timeslongerthan thoseon the voiceless
side.
comparisons
from only two of the sixcontinuawouldshow
audible differences in relative offset time.
The secondparameterthat wasmeasured
wasthe terminatingfrequency
of thefirstformant.Measurements
off 1
offsetfrequencywere made usingthe LPC analysesdescribed
above.TableIII givesF 1offsetfrequencies
for stimuli on opposite
sidesof thevoicingboundaryfor eachof the
sixcontinua.
In eachcomparisonF
1offsetfrequency
ishigher for the stimuluson the voiceless
sideof the boundary.
However,theeffectismuchlargerforthevowelswithhighfrequencyfirst formants.F I offsetfrequencydifferences
rangedfrom 76 to 258 Hz for stimuliin the environmentof
/e/ and/a/ but wereonly 17Hz for/i/and 23 Hz for/u/. In
fact, the first-formantcontoursfor the/pig/and/pug/
stimuliwereverynearlyflat;consequently,
little variationin
23
J. Acoc•t. Soc. Am., Vol. ?6, No. 1, July 1984
Althoughth/seffectwasquiteconsistent,
it is not immediatelyclearwhetherthesedecaytime differences
areaudible.
Van denBroeckeand van Heuven{1983)haveshownthat
the difference
!/men{DL) for decaytime canbe predicted
quiteaccurately(r ----0.99}fromreference
decayt/meby
DL ----0.2t -I- 6.07,
wheret is reference
decayt/me.The decaytimedifferences
measured from our stimuli exceeddifference limens e•timat-
edfromthisformulaforall comparisons
exceptforthestimuli drawn from the/pug/series.The differencein decaytime
for thispair was 19 ms,comparedto an estimateddifference
limenof 21 ms.For the/pig/continuum, however,the measureddecaytime differenceexceededthe estimatedDL by
only .1ms.
Hillenbrandoral.: Voiced-voicelesscontrast
23
IV. GENERAL DISCUSSION
abruptdrop in amplitudethan the corresponding
stimulus
on
the
voiced
side
of
the
boundary.
However,
in
some
vowel
To summarizebriefly,subjectswereaskedto identify
environments
the
differences
were
quite
small
in
relation
to
computer
editedCVCsendingin stops.
In general,
subjects
estimated
DLs
for
decay
time.
Again,
the/i/and/u/envitendedtochange
fromhearingvoicedstopstohearingvoicelessstopswhentheclosure
intervalanda portionofthevow- ronmentsshowedrelativelysmalldifferences.
el-to-consonant transition had been removed. Removal of
Taken as a whole, the acousticanalyseswere not as
definitive
as we had hoped: no singleacousticdimension
the finalburstsdid not significantly
alter the identification
separated
stimulion opposite
sidesof the voicingboundary
functions.
Experiment1 showeda smalleffectfor placeof
for
all
six
continua.
By
itself
this
kindof outcomeshouldnot
articulation.However,sincethiseffectwasnot replicatedin
experiment
2, it isnotclearwhether
theplaceofarticulation
of thefinalstopisan importantfactor.Theeffectfor vowel
environment
wasstatistically
significant,
but it is not clear
howthisfindingshouldbe interpreted.
The two continua
comeasa surprise.
Manyinvestigators
in thephonetic
per-
Basedon the measurements
of closurevoicing,it doesnot
sincetherewasno differencein voiceoffsettime for the/pig/
seriesandonly a 13-msdifferenceof the/pug/series.
ceptionareaareaccustomed
to thinkinglessin termsof unitary cuesto a contrastandmorein termsof tradingrelations
amonga numberof cues(seeRepp,1982for a review).The
that werebasedon vowelswith relativelylow first-formant resultsof thepresentstudy,however,do notappearto lend
wellto thiskindof description.
For example,it is
frequencies
--/i/ and/u/-- changed
fromvoiced
tovoice- themselves
less 10-15 ms earlier than stimuli in the environment of the
possibleto view abruptvowelterminationas a perceptual
thatcanbecuedby a highF 1offsetfrequency,
or
twohighF 1vowels.
Giventhepossibility
thatF 1offset
fre- dimension
by
a
short
decay
time,
or
by
some
appropriate
combination
quencymightbea voicingcue,wehadanticipated
a vowel
of thesetwo properties.Recallthat the/pig/and/pug/concontexteffectin theopposite
direction.
Wereasoned
thatif a
in F 1 offsetfrequency.
lowF 1 offsetfrequency
wasa cueto voicing,an inherently tinua showedvery smalldifferences
On
the
assumption
that
F
1
offset
frequency
anddecaytime
low firstformantmightfavorvoicedresponses.
The results
trade
against
one
another,
one
would
expect
to findthatthe
didnotconfirmthisprediction:
stimuliin thecontextof low
lack
of
contrast
in
F
1
offset
frequency
was
"compensated"
F 1vowels
showed
slightly
earliercrossovers
fromvoiced
to
voiceless.
It shouldbekeptin mind,however,
thateachcon- by a relativelylargecontrastin decaytime.Thiswasclearly
not the casesincethe differences
in decaytime for the/pig/
tinuumwasbasedona singlenaturallyproduced
token.For
thatreason,whatappears
to bea systematic
vowelcontext and/pug/serieswereat bestbarelyaudible.The trade-off
approach
could,of course,
beextended
onestepfurtherby
effectmightsimplyreflectidiosyncratic
characteristics
of
that gradualversusabruptvoweltermination
theparticular
tokens.
Wearecurrently
designing
a synthetic suggesting
tradesagainstanotherdimension,suchas relativeoffset
speech
studyto examine
voweleffects
in moredetail.
Acoustic analysisof stimuli straddlingthe voiced- time. A tradingrelationapproachwould suggestthat the
voiceless
boundaryprovidedfewdefinitiveanswers
regard- relativelysmallcontrastin F 1 offsetfrequencyand decay
by relativelylargedifferences
in
ingcuesto finalstopvoicingcontrasts.
However,theresults timewouldbecompensated
of these measurements do allow some tentative conclusions.
relativeoffsettime. The datado not supportthishypothesis
appearasthougha voicedclosureintervalis requiredfor
subjects
to reporthearinga voicedstop.This findingmay
provideat leasta partialexplanation
for the tendency
of
speakers
to devoice
relativelylargeamounts
ofclosure
intervals of syllablesending in phonologicallyvoiced stops
(Smith,1979;HoganandRozsypal,1980;FlegeandBrown,
1982).It appears
asthoughthetendency
of speakers
to devoiceis supported
by perceptual
strategies
on the part of
listenersthat do not rely on the presence
versusabsence
of
closurevoicing.
Acousticanalyses
werealsousedto investigate
thepossibilitythat subjects'
voicingdecisions
werebasedon the
mannerof terminationof the precedingvowel. The two
manifestations
of gradualversusabruptvoweltermination
that we investigated'were
the offsetfrequencyof the first
formantand amplitudedecaytime.Whenstimulion oppositesidesof thevoicingboundarywerecompared,largedifferences
in F 1offsetfrequency
wereseenonlyfor thestimuli
with relativelyhigh-frequency
firstformants.This suggests
that a relativelyhighF 1 offsetfrequencyis not a necessary
cueto theperception
of a voiceless
stop.It ispossible,
however,that F l offsetfrequencyplaysa role in somevowel
environments
but not others.A similarpatternwasseenin
thedecaytimemeasurements.
Forallsixcontinua,
thestimulus on the voicelessside of the boundaryshoweda more
24
J.Acoust.
Soc.Am.,Vol.76,No.1,July1984
One additional issue that deserves attention is the rela-
tionbetweenvoicingcuesfor initialstopsandthosefor final
stops.It hasbeensuggested
that the perception
of voicing
contrasts
in initial stopsisbasedon the resolutionof relative
onsettime (Pisoni,1977;seealsoMiller et al., 1976;Summerfield,1982;Hillenbrand,1984).Basedon the presentresuits, it does not seem likely that relative offset time is
stronglyinvolvedin the perceptionof finalstopvoicingcontrasts.There were many instancesin which stimuli werelabeleddifferentlywithoutshowingdifferences
in relativeoffset time. It is clear, however, that relative onset time is not
the only cueto initial stopvoicingcontrasts.Differencesin
the onsetfrequencyof the first formantalsoexerta strong
influenceon initial stop voicingjudgments.In general,low
F 1 onsetfrequenciestend to favor the perceptionof voiced
stopsand highF 1 onsetfrequenciestendto favor the perception of voiceless
stops(Lisker, 1975;Summerfieldand Haggard, 1977).The obviousfinal positionanalogof F 1 onset
frequencywouldbeF 1offsetfrequency.Wolf hasspeculated
that, "the amountof low-frequencyenergyin the vicinity of
onsetor offsetmay serveasa commonbasisfor the perception of the voicingdistinctionin initial and final position"
(1978,p. 299).Wolf's conclusions,
however,werebasedlargelyon experimentsusingstopsfollowing/ae/, a vowelwith
Hillenbrand
etal.:Voiced-voiceless
contrast
24
a high-frequency
firstformant.
Thepresent
results
suggest
thatF 1oilsetfrequency
differences
mayplaylittleornorole
whena stopfollowsa vowelwitha low-frequency
firstformant.
ACKNOWLEDGMENT
Derbock,M. (1977)."An acousticcorrelateof the forceof articulation,"J.
Phon. 5, 61-80.
Derr, M. A., andMasaaro,D. M. (1980)."The contribution
of vowelduration,F0 contour,andfricativedurationascuestothe/juz/-jus/distinction,"Percept.Psychophys.
27, 51-59.
Fant,C. O. M. (1962)."Descriptive
analysis
of the acoustics
of speech,"
LOGOS S, 3-17.
Flanagan,J. L. (1955)."A difference
limenforvowelformantfrequency,"
$.
Thisworkwassupported
by research
fundsfrom NIH
grantsT32NS07100-04and 5S05RR07028.
Acoust. Soc. Am. 27, 613-617.
Flege,J.,andBrown,W. S.(1982)."Thevoicingcontrastbetween
English
/p/and fo/as a functionof stressandposition-in-utterance,"
J. Phon.
10, 335-345.
•Although
voicing-dependent
vowelduration
differences
havereceived
a
gooddealof attentionin theliterature,it is importantto emphasize
that
largeeffectsare seenprimarilyin phrase-final
positionand in isolated
worda.Thesedifferences
are muchsmallerin nonphrase-final
position
(Umeda,1975;Klatt, 1973,1975,1976).Undercertainconditions
these
durational
differences
disappear
altogether
in connected
speech
(Crystal
andHouse,1982).
Fujimura,O., andLindqvist,J. (1971)."Sweep-tone
measurements
of vocaltract characteristics,"J. Acoust. Soc. Am. 49, 541-558.
Hillenbrand,J. (1984}."Perceptionof sine-wave
analogsof voiceonsettime
stimuli," J. Acoust. SOc.Am. 75, 231-240.
Hogan,$., and Rozsypal,A. (1980)."Evaluationof voweldurationasa cue
for the voicingdistinctionin the followingword-finalconsonant,"
J.
Acoust, SOc.Am. 67, 1764-1771.
A. (1961)."On voweldurationin English,"J. Acoust.SOc.Am.
2Tosimplify
thisreview,
wearerestricting
attention
to voicing
contrasts House,
1174-1178.
involvingpostvocalic
stopconsonants.
Otherstudieshaveexaminedthe
of cousonant
enviroleofvoweldurationin finalfricativevoicing
contrasts
(e.g.,Denes,1955; House,A. S.,andFairbanks,G. (1953)."The influence
ronmentupon the secondaryacousticalcharacteristics
of vowels,"J.
Derr andMassaro,1980,HoganandRozsypal,1980;PortandDalby,
1982;Massaro
andCohen,1983)andofstops
preceded
bynonvocalic
segments(Raphael
etal., 1975).
•It isverylikelythatvowel
duration
plays
a roleintheperception
offinal
stopvoicingwhenothervoicingcuesareambiguous.
A recentstudyby
Wardrip-Fruin
(1982b}
showed
thatvoweldurationbecomes
animportant
voicingcuewhenstimuliarepresented
in noise.
4Noattempt
wasmadetoseparate
thesteady-state
vowelfromthevowel-toconsonant
transitions.
The most'difficultsegmentation
decision
wasthe
boundary
between
thevoweloffsetandthestartofthestopclosureinterval.
Thisdecision
wasbased
ona dropinsignalintensity
anda smoothing
ofthe
waveform,
indicating
thatmostoftheradiatedenergy
isatornearthevoice
•Attenuation
isperhaps
abetter
wordthandisappearance.
Sweep-tone
measurements
by Fujimuraand Lindqvist(1971}haveshownthat a second
formantpeakisclearlypresent
in thevocal-tract
transfer
functionduring
stopocclusion
(seealsoFant, 1962,p. 13).However,thelevelofF2 issome
10dBlowerthanF 1.Thisfact,incombination
withthelow-frequency
bias
of theglottalsourcespectrum,
meansthatonlythefirstformantis visible
on a spectrogram
duringthe periodof time corresponding
to articulatory
occlusion.
Srhemeasurements
ofclosure
voicing
giveninTableIII willnotagree
with
valuesobtained
simplyby subtracting
thenominalamountof "voicingremoved"fromtheuneditedclosuredurationsreportedin TableI. Thereare
tworeasons
forthisdiscrepancy.
First,asindicated
in Sec.I A thenominal
stimulus
values
referonlyto thezero-amplitude
portionof theweighting
functions
thatwereusedintheeditingprocedure.
Sincethenominalstimulusvaluesdo not takeintoaccountthe 15-mslineardecayfunction,these
values
willunderestimate
theamount
ofclosure
voicing
thatwasanenuat-'
ed.Second,the closurevoicingmeasurements
givenin TableI werebased
onosciHograms
whilethosein TableIII werebasedon LPC deriveddigital
spectrograms.
(Reasons
for switchingto the frequency-domain
technique
are explainedin Sec.IlI.) Thesetwo methodsshouldproducesimilarbut
Acoust.So:. Am. 25, 105-113.
Klatt, D. H. (1973)."Interactionbetweentwo factorsthatinfluence
vowel
duration,"J. Acoust.So:. Am. 54, 1102-1104.
Klatt, D. H. (1975)."Vowel lengtheningis syntacticallydeterminedin a
connecteddiscourse,"J. Phon. 3, 129-140.
Klatt, D. H. (1976)."Linguisticusesof segmental
durationin English:
Acousticandperceptual
evidence,"
J. Acoust.Soc.Am. 59, 1208-1221.
Lisker, L. (1975I. "Is it VOT or a first-formanttransitiondetector?,"$.
Acoust. Soc. Am. 57, 1547-1561.
Lisker,L., andAbramson,
A. S.(1964}."A cross-language
studyof voicing
in initial stops:Acousticalmeasurements,"
Word 20, 384-422.
Lisker, L., and Abramson,A. S. (1967)."Someeffectsof contexton voice
onsettimein Englishstops,"Lang.Speech10, 1-28.
Lisker,L., andAbramson,A. S.(1970)."The voicingdimension:
Someexperimentsin comparativephonetics,"in Proceedings
of the6th InternationalCongress
of Phonetic
Sciences,
Prague,1967(Academia,Prague),
pp. 563-567.
Mal6cot,A. (1958)."Theroleof releases
in theidentification
of released
final stops,"Lang.34, 370-880.
Mallcot, A. (1970)."The lenis-fortis
oppostion:
Its physiological
parameters,"J. Acoust. SOc.Am. 47, 1588-1592.
Markel,J.,andGray,A. (1976}.LinearPrediction
ofSpeech{Springer-Verlag, New York).
Massam,D. M., and Cogen,M. M. (1983)."Consonant-vowel
ratio:An
improbable
cuein speech,"
Percept.Psychophys.
33, 501-505.
Mermelstein,P. (1978)."Differencelimensfor formant frequencies
of
steady-state
andconsonant-bound
vowels,"J. Acoust.Soc.Am. 63, 572580.
Miller, $. D., Wier, C. C., Pastore,R. E., Kelly, W. J., andDooling,R. J.
(1976)."Discrimination
andlabelingof noise-buzz
sequences
with varyingnoise-lead
times:An exampleof categorical
perception,"
J. Acoust.
SOc.Am. 60, 410-417.
O'Kane,D. (1978I. "Mannerof vowelterminationasa perceptual
cueto the
voicingstatusof post-vocalic
stopconsonants,"
J. Phon.6, 311-318.
?Since
dataarenotavilableon thediscrimination
of F 1 offsetfrequency
Parker,F. (1974)."The coarticulation
of vowelsandstopconsonants,"
J.
differences,
speculations
about audibilitymust rely on differencelimen
Phon. 2, 211-221.
data usingstimuliwith stationaryformants.The smallestestimateof the
R.E.(i983).
"'remporal
order
judgment
ofauditory
stimulus
offdifference
limenfor first-formant
frequency
is 15Hz, basedon a reference Pastore,
set,"
Percept.
Psychophys.
33,
54-62.
sigualwith a 300-Hz F 1 (Flanagnn,1955).Mermelstein(1978),however,
Peterson,
G., andLehiste,I. (1960)."Durationof syllablenucleiin Engusedsimilarstimuliandfounda 50*Hz difference
limenfor F 1.Evenusing
lish," J. Acoust.SOc.Am. 32, 693-703.
thesmallerestimate
provided
by Flanagan,
the 17-and23-Hzdifferences
Pisoni,D. B. (1977)."Identificationanddiscrimination
of therelativeonset
measuredfrom our stimuli would bejust detectablein a same/different
not necessarilyidentical results.
timeof two-component
tones:Implications
for voicingperception
in
task.
stops,"J. Acoust.SOc.Am. 61, 1352-1361.
Port,R. F., andDalby,F. (1982)."Consonant/vowel
ratioasa cuefor voic-
Chen,M. (1970)."Vowellengthvariationasa functionof thevoicingof the
consonant environment," Phonefica 22, 129-159.
Crystal,T. H., and House,A. S. (1982)."Segmentdurationsin connected
speech
signals:
Preliminaryresults,"J. Aconst.Soc..•m. 72, 705-716.
Denes,P. (195S)."Effectof durationon the perceptionof voicing,"J.
Acoust. SOc.Am. 27, 761-764.
25
J. Acoust.Soc. Am., Vol. 76, No. 1, July 1984
ingin English,"Percept.Psychophys.
32, 141-152.
Raphael,L. J. (1972)."Preceding
voweldurationasa cueto theperception
ofthevoicing
characteristic
of word-final
consonants
in AmedcanEnglish," J. Acoust. So:. Am. 51, 1296-1303.
Raphael,L. J.(1981)."Durations
andcontexts
ascuestoword-final
cognate
oppositionin English,"Phouetica•1, 126-147.
Raphael,L. J.,Dorman,M., Freeman,F., andTobin,C. (1975)."Voweland
Hillonbrandeta/.: Voiced-voicelesscontrast
25
nasaldurationascuesto voicingin word-finalstopconsonants:
Spectrographicand perceptualstudies,"J. SpeechHear. Res.18, 389-400.
Raphael,L. J., Dotman,M, F., andLiberman,A.M. {1980)."On denning
thevoweldurationthat cuesvoicingin finalposition,"Lang.Speech23,
sants,"J. Acoust. Soc.Am. 62, 435-448.
Umeda,N. (1•F/5)."Voweldurationin AmericanEnglish,"I. Acoust.
Am. S8, 4?.
297-307.
Repp,B. H. (1982)."Phonetictradingrelationsandcontexteffects:
New
evidencefor a phoneticmodeof perception,"Psychol.Bull. 92, 81-110.
Revoile,S., Pickett,J. M., Holden, L. D., and Talkin, D. (1982)."Acoustic
cuesto finalstopvoicingfor impaired-andnormal-hearing
listeners,"
•.
Acoust. Soc. Am. 72, 1145-1154.
Rositzke,H. A. (1943)."Thearticulationof finalstopsin generalAmerican
speech,"Am. Speech18, 32-42.
Smith,B. L. (1•/9). "A phoneticanalysisof consonant
devoicingin children'sspeech,"I. Child Lang.6, 19-28.
Summerfield,
Q. (1982}."Differences
between
spectral
dependencies
in auditoryandphonetic
temporal
processing:
Relevance
totheperception
of
voicing
in initialstops,"
•. Acoust.Soc.Am. 72,51-61.
26
Summerfield,
Q., andHazard, M.P. (19•7)."On thedissocintion
of spectral and temporalcuesto the voicingdistinctionin initial stopconson-
J. ^coust. Soc. Am., Vol. 76, No. 1, July 1984
van denBroecke,M.P. R., and van Heuven,V. J. (19•3). "Effectand artifactin theauditorydiscrimination
of riseanddecaytime," Percept.Psychophys.33, 305-313.
Walsh,T., and Parker,F. (1981}."Vowelterrain*lionasa erieto voicingin
post-vocalic
stops,"J. Phon.9, 105-108.
Wardrip-Fruin,C. (1982s)."On thestatusof temporalcuesto phoneticca-
tegories:
Preceding
voweldurationasa cueto voicingin finalstopconsonants,"J. Acoust. Soc.Am. 71, 187-195.
Wardrip-Fruin,C. (1982b)."Final stopvoicing:Vowel durationthe primarycuei•noise•"paperpresented
at theAmericanSpeech
andHearing
Association Convention, Toronto, November, 1982.
Wolf,C. (1•/81."Voicingcuesin Englishfinalstops,"•. Phon.6, 299-309.
Hillonbrandetal.: Voiced-voicelesscontrast
26