Effectsof postlingual deafnesson speechproduction: Implications for the role of auditory feedback Robin S. Waldstein a)

BrownUniversity, Department ofCognitive andLinguistic Sciences, Providence, Rhode/s/and 02912

(Received5 October1989;acceptedfor publication16July 1990)

Thisstudyinvestigated someeffectsof postlingual deafness on speech by exploringselected properties of consonants, vowels, andsuprasegmentals in thespeech of seventotally, postlingually deafened individuals. Theobserved speech properties included parameters that functionasphonological contrasts in English,aswellasparameters thatconstitute primarily phoneticdistinctions. Theresultsdemonstrated thatpostlingual deafness affectsthe production of all classes of speech sounds, suggesting thatauditoryfeedback isimplicated in regulating thephonetic precision of consonants, vowels, andsuprasegmentals overthelong term. In addition,the resultsare discussed in relationto factorsthat may influencethe degree of speechimpairment,suchasageat onsetof deafness. PACS numbers: 43.70.Dn, 43.66.Sr

INTRODUCTION

A long-standing issuein speechresearchconcernsthe extentto whichspeakers makeuseof the informationavailableto themby auditoryfeedbackin orderto producehighqualityspeech.It is generallythoughtthat the relativeimportanceof auditoryfeedbackchanges duringthe courseof development(e.g., Lane and Tranel, 1971;Borden,1979). Specifically, auditoryfeedback isviewedascrucialto speech soundacquisition; in learningto speak,childrenmustmodel their ownoutputto the speechof othersthroughthe useof auditoryfeedback.Oncethe soundsof speechhavebeenacquired,however,auditoryfeedbackis typicallythoughtto becomelessimportant,servingto regulateprimarily the suprasegmental propertiesof speech,which are thoughtto havelessalternatefeedbackinformation, while the segmen-

tal propertiesare largelycontrolledby tactileand/or proprioceptive feedback(e.g.,Ladefoged,1967;but seeBorden, 1979). Thesehypotheses havebeenbasedon the resultsof short-term auditory feedbackmanipulation studieswith normally hearingsubjects. Another approachto the studyof the role of auditory feedbackduring skilledspeechproductionis to observethe consequences on speechof total deafnessacquiredpostlingually.The speechcharacteristics of thispopulationcanprovide insightinto the role of auditory feedbackmonitoring over the longterm and, in sodoing,evaluatethe hypotheses that have been advanced on the basis of the short-term

feed-

back manipulationstudies. Recent instrumental researchon suprasegmentalparametersin the speechof postlinguallydeafenedindividuals isgenerallyconsistent with thepredictions madebythefeedback manipulationstudieswith normally hearingsubjects;

specifically,significantlyhigherF0 values(Leder et al., 1987a),aswell asincreasedF0 variability(Lane, 1988) relative to normal, are found. In addition, relative to normal Currentaffiliation:McGill University,Schoolof Human Communication Disorders,1266Pine Ave. W., Montreal, QuebecH3G 1A8, Canada.

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J. Acoust.Soc. Am. 88 (5), November1990

values, significantlylonger syllable (Leder et al., 1987b; Lane, 1988), sentence(Leder et al., 1987b), and paragraph durations(Leder et al., 1987b;Lane, 1988), andtotal pause time and pausedurations(Lane, 1988) havebeenreported. Higher overallrelativeintensitylevelsin sentences (Leder et al., 1987c) have also beenfound in postlinguallydeafened speakers'productions;at the sametime, however,Leder et al. (1987c) noted relative preservationof the linguistically governeduseof intensityto signalthe beginningsand endingsof breathgroupsand phrasesin the postlinguallydeafenedspeakers'productions.In general,thesepatternshold both for individualspostlinguallydeafenedduring adulthood, as well as for those deafened in childhood (Binnie et

al., 1982;Plant, 1983;Plant and Hammarberg, 1983). Although lesssystematicallystudied,there is evidence that suggests an effectof postlingualdeafnesson voweland consonantproduction.For example,Cowie and DouglasCowie(1983) conducteda descriptiveperceptualanalysisof the speechof 12 postlinguallydeafenedindividuals.Among the errors noted, the most common involved substitutionsof

voicedfor voiceless plosivesandlabiodentalfricatives,anda tendencyfor vowelsalong the acute axis to be centralized; that is, [i ] tendedto soundmorelike [ I ], and the vowel [ e] wasoften perceivedas [ •e] and [ a ]. Further, in an acoustic studyof the speechof threepostlinguallydeafenedindividuals, Lane (1988) noted a greater degreeof breathinessin vowelproductionanddeviations in intrinsicvowelpitchpatterns;in addition,productionof the fricativesIs] and [•] were characterizedby a smaller distinction between the centersof gravityfor thesetwo segments. Finally, Zimmermann and Rettaliata ( 1981) notedlongermovementdurations of articulatory gesturesin a kinematic study of the speechof onepostlinguallydeafenedadult. Thus studiesof the speechof individualswho were postlinguallydeafened suggest that auditoryfeedbackis activeoverthe longterm in monitoring speechsegmentproductioneven in adulthood. Moreover,thereare someindicationsthat postlingualdeafnessoccurringduringthelater childhoodyearsmay resultin

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greaterdeviationsin segmentalparametersthandoesa lateroccurringloss(Cowieet al., 1982;PlantandHammarberg, 1983). For example,in a studyof speechintelligibilityin 12 postlinguallydeafenedindividuals(Cowie et al., 1982), the speakerswho receivedthe lowestintelligibilityscoreshad acquiredtheirhearinglosses at theyoungest ages(beforethe ageof about 10), while speakerswho receivedthe highest intelligibilityscoreshad becomedeafafter the ageof about

dition, the presentstudyinvestigatestwo differentmeasures of vowel duration.

Previous research has shown that abso-

lute voweldurationsare elongatedin the speechof postlinguallydeafenedindividuals(e.g., Binnie et al., 1982). In the presentstudy, measuresof absolutevowel duration,which are nonphonemicin English,are comparedto measuresof contextuallyconditionedvowel duration, which serveto distinguishthe voicingof the following consonant,and hence 18. bear a phonemicfunction (Petersonand Lehiste, 1960;RaThe goalof thepresentstudyisto systematically charac- phael, 1972). Deviationsaffectingabsolutevoweldurations, terizethe effectsof postlingualhearinglosson speechin an but not contextually conditioned vowel durations, would attempt to evaluatethe role of auditory feedbackduring suggesta phoneticdeficit,while deviationsaffectingcontexspeechproductionoverthe longterm.Thisinvestigation extually conditionedvowel duration measuresas Well would aminesbothspectralandtemporalproperties of consonants, indicatea deficitthat is alsophonemicin nature. vowels,and suprasegmentals in the speechof seventotally, Finally, suprasegmental productionis explored,focuspostlinguallydeafenedindividualsin an effort to determine ing on fundamentalfrequencycharacteristics.While averwhetherthereis an across-the-board effecton thesespeech ageF0 hasbeenreportedto be higher in the postlingually soundclasses, or whetherthesespeech parameters areselec- deafenedrelativeto normals(Leder et al., 1987a),the prestively affectedby a long-termlossof auditoryfeedback.Paent study employsadditional measuresto further describe rametersthat functionasphonological contrasts in English F0 patterningand variabilityin this population.The useof aswell asparameters that constituteprimarilyphoneticdis- F0 asa linguisticcueto signalphrasestructureisalsoinvestitinctions will be included in order to determine whether gated. To this end, F0 contours of declarative sentences, postlingual deafness resultsin deviations that compromise yes/no questions,and wh-questionsare derived,and the diphonological integrity,or whetherprimarilyphoneticdevia- rectionof the terminal portion of the contouranalyzed.A tions are observed,leavingphonologicaldistinctionsrelacomparisonof the phoneticand linguisticallyrelevantfunctions of F0 should indicate whether the disturbances noted tively spared. The presentstudy investigatesthe voice-onsettime are mostlyphoneticin nature, or whetherthe linguisticuse (VAT) distinctionin stop consonantproduction,which of F0 is affectedaswell by postlingualdeafness. contributesto the phonemiccontrastof voicing.Previous Accordingto the hypothesesadvancedin earlier studresearchhasfocusedrelativelylittle attentionon the role of ies,we shouldexpectto find the largestdeviationsfrom the auditoryfeedback duringconsonant production, asit isgen- normallyhearingspeakersin the suprasegmentals, but relaerally arguedthat consonantproductionis associated with tive preservationof voweland consonantproduction. greatertactilefeedback,andhencelesssusceptible to beinfluencedby the lossof auditoryfeedback(e.g., Ladefoged, I. METHODS

1967).However,thetimingrelationship involvedin theproductionof voicingin stopconsonants(i.e., the time between the release of the oral closure and the onset of vocal fold

vibration) hasbeenshownto be vulnerableto prelingual hearinglossand to be significantlycorrelatedwith the degree of the loss (Monsen, 1976). An examination of the VaT distinctionin stopconsonantproductionin the speech of postlinguallydeafenedindividualsshouldrevealwhether this feature is preserveddespitepostlingualdeafness,or whetherit is alteredas a resultof a postlinguallossas well. Changesin the VaT functionsof postlinguallydeafened

speakerswouldsuggestthat auditoryfeedbackis employed to monitor the voicingfeatureduring stopconsonantproduction,evenafter it hasbeenacquirednormally. The effectsof postlingualdeafness on vowelproduction are also exploredin this study. Measuresof both formant frequencies and segmentdurationsare derived.While preliminary observations of theseparametershavebeenmadein previous studies (Plant, 1983; Plant and Hammarberg, 1983), the presentstudyexploresthesemeasuresmoresystematicallyto betterdefineany changesobserved.A comparisonof the formantfrequencyvaluesdisplayedby postlingually deafenedspeakersrelative to thosedisplayedby normallyhearingspeakersshouldindicatewhetherthe two groupsaim for functionallyequivalentvoweltargets.In ad2100

J. Acoust.Soc. Am., Vol. 88, No. 5, November1990

A. Subjects

Sevenpostlingually,profoundly deafened (• 120 dB HL 3-freq.av) nativeEnglishspeakersparticipatedin this study.All subjectslosttheirhearingsuddenlyaftertheageof 5, but differedin ageat onsetof hearinglossand in current age. D 1 wearsa hearingaid at schoolaccordingto school policy;none of the other subjectswore aids at the time of testingor for a periodof time longerthan 3 monthsfollowing the onsetof deafness. All subjectsusespeechregularlyto communicate. SevennormallyhearingnativeEnglishspeakers, matchedto the current age of the deafenedspeakers, servedasa controlpopulation.TableI providesinformation on the two subjectgroups. B. Stimuli and procedure

Experiments1 and 2 exploredselectedacousticproperties of stop consonantsand vowels.The stimuli for these tasksconsisted of monosyllabic wordsthat wereprintedon 5-in.X 8-in. cardsfor subjectsto readaloud.If subjectswere unableto reada word,the experimenter provideda spoken, signed,and/or fingerspelled modelto be orally repeated. For the consonantanalyses,30 CVC(C) words were elicited.Thesewordsconsistedof fivewordseachcontaining eachof the six stopconsonants[b d g p t k] precedingthe

RobinS. Waldstein:Postlingualdeafnessand speechproduction

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TABLE I. Profilesof subjectstested.

20-kHz samplingrate with a 9-kHz low-passfilter, since their fundamentalfrequencies werehigher. Analysisof thestopconsonantstimuliproceeded asfollows. Voice-onsettime, or VaT, valueswere obtainedby measuringthe period of time in ms from the start of the burst,signalingreleaseof theoral closure,to the firstsignof periodicity,signalingthe onsetof voicing.In tokenswhere

Age at onset

SubjectSex

of deafness Currentage Yearsdeaf Etiology

D1 D2

F M

6 8

13 45

D3 D4

F F

11 16

52 44

D5 D6

M F

18 30

28 40

D7 H1 H2

F F M

40

60 13 46

H3 H4 H5 H6 H7

F F M F F

7 37 41

meningitis meningitis meningitis

28

unknown

10

ototoxicdrug

10

unknown

20

ototoxicdrug

there was voicinglead, measurementswere made from the onsetof periodicityto the startof the burst. (Twenty tokens, for which there was no visible releaseburst, were excluded from the analysis.) With regard to the vowel stimuli, the first two vowel

56 44

formantfrequencies werecalculated usinglinearpredictive codingwith a 14-polenetworkfor adultsand a 24-pole networkfor children,by positioninga 25.6-msfull-Hammingwindowat the midpointof the vowel.In tokenswhere

28 41 62

either F 1 or F2 could not be obtained, the window was

moveda maximumof 25 msto the left or right of the midpointandanotherLPC analysisconducted.(Ten tokens,for which either F 1 or F 2 could not be derived after the second

attempt,wereomittedfrom the data pool.) Vowel duration vowel [a]. The final consonantvariedin order to createreal wordsof English. Each word was repeatedfour times in a

randompresentation, yieldinga totalof 20 tokensof eachof six stopconsonants, or a total of 120tokensper speaker. For the vowel formant frequencyand intrinsicduration analyses,a seriesof eight/hVd/words waselicited,containingthevowels[i • e ae^ a u u ]. Eachwordwasrepeatedeight timesin a randompresentation, yieldinga total of 64 tokens perspeaker. A secondseries,consisting of theeightvowels[i • e eo u ae^ ] producedin thecontexts/bVd/and/bVt/, was alsoelicitedfor measuresof contextuallyconditionedvowel duration effects.Thesewordswere repeatedin random order fivetimeseachfor a total of 80 tokensper speaker. Experiment 3 investigatedsomesuprasegmental properties of words and sentences. The sentence material

for this

task consistedof declarativestatements,yes/no questions, and wh-questions,which were printedon 5-in.X 8-in. cards for subjectsto readaloud (e.g., The dogran outside.Did the dog run outside?Why did the dog run outside?).Four tokensof eachsentencetype were presentedin random order for a total of 12 utterancesper subject.In addition, one monosyllabicnoun from eachsentenceclusterwas selected and repeatedtwice for a total of eighttokensper subjectfor usein an F0 jitter analysis. Subjectswere recordedindividuallyin a quiet room usinga Nagra4.2 reel-to-reeltaperecorderanda ShureSM 81 condensormicrophone,positionedapproximately12 in. from thespeaker's mouth.Testingtimelastedapproximately 30 min. C. Analyses

The resultingtapeswereanalyzedon a PDP 11/34 computer usingBLISS programs(Mertus, 1984) in the PhoneticsLaboratoryat Brown University.The tokensfor the adult speakers(D2-7 and H2-7) weredigitizedat a 10-kHz sampling rate, with a 4.5-kHz low-passfilter and 10-bit quantization.Tape recordingsfor the two youngestspeakers(D 1 and H1 ), however,who were age 13, were digitizedusinga 2101

J. Acoust. Soc. Am., Vol. 88, No. 5, November 1990

valuesfor eachof the two stimulussetswereobtainedby measuringfrom the firstsignof periodicityin the waveform to the onsetof the closureintervalfor the followingconsonant.

Stimulifor the suprasegmental analysesweremeasured in the followingmanner.The duration of eachsentencewas measured.Intonationcontourswereobtainedusingan autocorrelation algorithm with a 25.6-ms window and 10-ms window movement;the resultingfrequencycontourswere used to determine whether the direction of the terminal was

appropriatefor the sentencetype. Mean fundamentalfrequencyvaluesand standarddeviationswere calculatedfor each sentence;in addition, F0 maximum, minimum, and rangevalueswere obtained.F0 jitter analysisof the words spokenin isolationwascompletedby determiningthe standard deviationsof the distancebetweensuccessive(adjacent) pitch periodsfor the entire durationof eachword.

II. RESULTS

AND DISCUSSION

A. Experiment 1. Voice-onset time in word-initial stop consonants

1. Normally hearing subjects

Figure 1(a) illustratesa typical VaT distributionfor the alveolarstops[d t] as producedby subjectH2. As expected,the figureshowstwo clear-cut,nonoverlapping categoriesin the productionof the voicedand voicelessstops.In thisfigure,asin eachsubject'scontinuum,the two categories are separatedby a marginof at least20 ms. Similarresults were found for all three placesof articulation.Table II presentsthe ¾OT meansand rangesfor all subjects. As Table II shows,in the hearingsubjects'productions, the voicedcategoriesresidepredominantlyin the short-lag region,rangingbetweenvaluesof 0-24 msfor [b l, 2-32 ms for [d l, and 10-42 ms for [g]. Voicing lead, or prevoicing, was producedby four of the sevenspeakers(H3-H5, and H7); thesevaluesrangebetween - 163 to - 44 msfor [b l,

Robin S. Waldstein:Postlingualdeafness and speech production

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{b) D1 [d]/[t]

{a) H2 [d]/[t]

_

,4

4

-

2

0

,,,[

-150

....

-100

I .... -50

I, 0

VOT

IN

50

100

150

-150

-tOO

-50

US

0 V0T

{c) D2 [d]/[t]

IN

50

100

150

MS

{d) D3 [d]/[t]

_

--_

2

0 -150

-tOO

-50

0 V0T

IN

50

100

150

-

0 .... --150

I .... -100

I .... -50

MS

0

50

100

150

50

100

150

50

100

150

VOT IN MS.

{e) D4 [d]/[t]

{f) D5 [d]/[t]

8

6

6

-

4

4

-

2

2

-

-

50

-100

-50

0 V0T

IN

50

100

150

-150

-100

-50

MS

0 V0T

{g) DO [d]/[t]

IN

MS

{h) D7 [d)/[t)

10

lO

8

--

6

-

4

-

8

6 _ 4

2

-15o

-lOO

-50

o V0T

IN

100

150

MS

-150

-tOO

-50

0 V0T

IN

MS

FIG. 1.VOT distributions for thealveolarstops[ d t ] for (a) subjectH2, representative of thehearingspeakers, andfor (b)-(h) eachdeafenedsubject.Open barsrepresent[d ] tokens;closedbarsrepresent[ t ] tokens. 2102

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TABLEII. VOTmeans andranges (inms)fornormally hearing andpostlingually deafened subjects.

Subject H1 H2

[b]

[d]

[t]

[g]

[k]

12

102

20

111

25

108

(0-24)

(60-153)

(6-28)

(85-173)

(16-37)

(64-141)

12

96

27

105

25

107

(8-20)

(73-116)

(19-34)

(78-138)

(13-38)

(80-130)

H3

-- 86/9

73

-- 94/10

82

26

89

( -- 125--- 44/

(55-96)

( -- 122--- 69/

(53-124)

(14-42)

(72-123)

0-15)

H4

2-16)

-- 152/11

99

13

96

22

102

( -- 163--- 141/

(74-136)

(4-19)

(65-114)

(12-36)

(90-118)

1-21)

H5

[p]

-- 80/13

81

15

89

24

89

( -- 84-- 76/

(44-119)

(8-32)

(71-105)

(18-37)

(62-119)

5

78

14

79

16

78

(0-9)

(36-130)

(8-20)

(44-112)

(10-24)

(48-128)

H7

-- 118/5

78

-- 112/15

93

-- 151/23

93

( -- 169--- 68/

(50-115)

( -- 142--- 65/

(65-138)

( - 179--- 108/

(73-114)

X

0-14) -- 109/10

( -- 163--- 44/

6-24)

H6

87

8-22) -- 103/16

(36-153)

( -- 142--- 65/

94

14-33) -- 151/23

95

(44-173)

( -- 179--- 108/

(48-141)

0-24) 21

(9-60) D2

-- 88

( -- 145--- 54)

(20-36)

( -- 126--- 60)

(20-35)

( -- 148--- 54)

(30-43)

D3

10

35

20

42

19

46

(0-22)

(21-51)

(11-28)

(28-66)

(13-25)

(35-60)

D4

6

41

12

49

19

52

D1

31

2-34) 37

50

10-42) 33

(18-39)

(26-49)

(33-79)

(18-66)

(24-71)

26

-- 86

26

-- 97

36

43

(0-15)

(25-59)

(6-16)

(31-66)

(14-24)

(37-76)

D5

-- 90/4

40

-- 70/8

44

-- 83/22

61

(--117- -- 29/

(17-64)

( -- 70/

(29-60)

(--83/

(46-95)

D6

0-10) 6

(0-13) D7

46

0-15) 14

52

9-43) 25

(7-85)

(6-22)

(15-75)

(844)

(45-105)

4

108

16

118

19

108

(1-7)

(73-178)

(10-30)

(70-166)

(10-34)

(73-153)

65

-- 142to -- 65msfor [d], and - 179to -- 108msfor [g]. In summary,the data obtainedfrom the hearingsubPrevoicingoccurslessfrequentlyas placeof articulation jectsin thisstudyarecomparable tothosereported byLisker movesfurtherbackin thevocaltract,i.e.,labialto alveolarto andAbramson(1964) andbyZlatin (1974) for stopconsovelar.Wheneverprevoicingis observed in a distribution, nant production. however, short-lag stopswerealsoproduced asmembers of the voicedcategory; in otherwords,no speakerexhibited onlyprevoiced tokensforthevoicedcategory. Thevoiceless 2. Postlinguallydeafened subjects categories occurbetween valuesof 36-153msfor [p], 44The VaT distributions for the alveolarstopsaspro173msfor [ t ], and48-141 msfor [k ], andareconcentrated ducedby the postlingually deafened subjects are shownin

in thelong-lag regionofthecontinuum. Further,lookingat theranges ofbothvoicedandvoiceless stopsacross thenormally hearingsubjects,it is clear that, while individuals showeddifferentabsolutevaluesof VaT, no individual

Fig.1(b)-(h); dataforallplaces ofarticulation arepresented in Table II. On balance,bimodaldistributionsare evident in the data;nevertheless, somedistinctionsbetweenthe deaf-

enedandthehearingspeakers' productions canbeobserved.

showed overlap between anyofthevoiced/voiceless pairsat

Themostapparent overalldifference is a tendency for the anyplaceofarticulation. Finally,placeofarticulation effects voiceless stops tobeshortened. Withtheexception ofsubject are evidentin thesedata, as longerVaT valueswereob- D7, thepostlingually deafened speakers' voiceless category servedfor the alveolarandvelarstopsrelativeto the labial for all threeplacesof articulation isshiftedleftward,i.e.,to stops. shorterVaTs. Therangevaluesin TableII confirmthat,for 2103

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speech.It is an empiricalquestionwhethervoiceless stops wouldbe producedwith shorterVaTs in the spontaneous speechof postlingually deafened individuals,ashasbeenreportedto occurin thespontaneous speechof normallyhearing subjects(Lisker and Abramson,1967). more restrictedthan that observedin the normally hearing Despitethe overallfindingof shortenedvoiceless VaT subjects' distributions. In contrast,tokensrepresenting the values,it wasalsoapparentthat, with the exceptionof the voicedcategories occurin theexpected short-lagregionfor subjectsD 1 and D2, two clear-cutcategories, locatedin rethe majorityof subjects(D3-D7) and are comparable to gionsthat reasonably approximate thosefoundwith normalthoseobserved in thehearinggroup,asreflectedin themean ly hearingsubjects, emergein thedistributions ofthepostlinandrangevaluesprovidedin TableII. Despitethesmaller. gually deafenedspeakers,suggesting that the phonemic degreeof separation betweenthevoicedandvoiceless cate- contrastof voicingis relativelyspared.Nonetheless, the regories,however,thesesubjects domaintaina bimodalVaT sultssuggestthat auditoryfeedbackservesto fine-tunethe distribution. Finally,placeof articulationeffects areevident VaT valuestypicalof Englishin adulthood. in eachsubject'scontinua.

subjects D l-D6, thevoiceless stopsrarelyreachedthelonglagvaluescharacteristic ofthehearingsubjects, andtheendpointswereshorterthanthoseproduced bythehearingsubjects. Specifically,the majority of voicelesstokenslie between30 and50 ms,a rangethat isbothdifferentfrom and

It is noteworthy that, in addition to the shorter and

morerestrictedvoiceless category, 'twoof the subjects(D 1 andD2) alsodisplayedaberrantvoicedcategories. A lookat Fig. 1(b) and (c) and at Table II revealsthat, for D 1, the voicedcategories are locatedat longerVaT valuesrelative to normal, resultingin a great deal of overlapbetweenthe voicedand voicelessphoneticcategories.D2, on the other hand,producesall voicedtokenswith muchprevoicing.In contrast,in the distributionsof the hearingsubjectswho exhibited prevoicing,short-lag values were also produced. Thus,whileD2 displaystwo nonoverlapping voicingcategories,neithercategorycorresponds to that typicallyseenwith nativeEnglish-speaking normallyhearingsubjects. Interestingly, subjectsD 1 and D2 were deafenedat the youngest ages(during childhood).

3. Discussion

B. Experiment 2. Vowels 1. Formant frequency analyses

a. Normallyhearingsubjects. Figure2 (a) depictsa typi-, cal acousticvowel spacefor the normally hearingsubjects (from subjectH5), obtainedby plotting the first- and second-formantvaluesfor eachindividual.While somesubjectto-subjectvariability was evident,it was clear that for each speaker,eachvoweloccupiesa well-definedlocusand is discrete from

the other vowels within

the individual's

vowel

space.The vowels[i] and [ u], in particular,havecircumscribedloci in the extremeleft upperandlowercornersof the triangle.Occasionaltokensof onevowel may overlapinto a neighboringvowel's region, but this only occurswith, at most, two tokens of a given vowel. The vowelsalong the acuteaxisconsistentlyfollow the sequence[ i • e •e], and the vowelsalongthe graveaxisare consistentlyordered[ u u a].

The location of the vowel [^] relative to the other vowels varies from subjectto subject,but is consistentlysituated nant productionas a meansof investigating the conse- betweenthe acute and grave axes. In general,thesevalues quences ofpostlingual deafness onthecomplex coordination correspond to those reported by Peterson and Barney betweenvoicingonsetandclosurerelease.The resultssug(1952), with the possibleexceptionof [^], whichtendedto gestthatcontrolof thisaspect of thevoicingfeatureissub- be lesscentralizedin this study. jecttotheeffects ofpostlingual deafness. Withtheexception b. Postlinguallydeafenedsubjects. Figure2(b)-(h) dis-

The consonantal analysesmeasuredVaT in stopconso-

of D7, the locationof eachpostlingually deafened subject's playsthe vowelspacesfor the postlinguallydeafenedsubvoiceless categories alongthe VaT continuum wasshifted jects.A lookat thesefiguressuggests that, for themajorityof leftward to shortervalues,with the resultthat the voiceless

tokensoftenfellin theregionwherefewoccurin thenormal-

ly hearingsubjects' data.Thesefindings suggest thatauditoryfeedback serves to monitorcontrolof thisaspectof laryngeal timingeveninadulthood, afterthefeatureofvoicing is firmlyestablished, to maintainphoneticprecision. It is noteworthythat it is the voiceless cognatewhichappearsto bemorevulnerable to postlingual hearingloss;thiscognate is alsoacquiredlater than the voicedcounterpart,presumablybecause it is moredifficultto produce(Kewley-Port andPreston,1974;ZlatinandKoenigsknecht, 1976).A similar effectof shortening of thevoiceless counterpart hasbeen observed in thespeechof prelinguallydeafspeakers (Monsen, 1976).

A consequence of the shorterVaT valuesfor voiceless stopsisthat thetwo voicingcategories exhibitedby thepostlinguallydeafenedindividualswerelessdiscrete.It is worth noting that these resultswere obtained in citation-form 2104

J. Acoust.Soc.Am.,Vol.88, No.5, November1990

subjects,the vowelsfollow the sequence alongthe acuteand grave axes that is typically seenwith normally hearing speakers;however,in general,the vowel spacesfor these speakers aremorerestrictedin range,andthevowelsareless discretelypositionedwithin the space,relativeto normal. Individualdifferences emerge,however,with respectto both of theseobservations; for example,subjectsD3 and D5 display relatively discretevowelseven though the acoustic spacebetweeneachlocusisreduced,andsubjects D2 andD3 exhibit more extremevowel spacereductionsthan do the otherspeakers. Further,thevowel[i] hasa lowerF 2 relative to the other vowelsin eachspeaker'sacousticvowelspace than is normally found with hearingspeakers. Theseimpressions are confirmedby an examinationof TablesIII and IV, which providemeanformant frequency values, standard deviations, and range values for each speakerforF 1andF 2, respectively. [Overallmeansforeach vowelfor eachgroupwerenot computed,sincethe subjects

RobinS. Waldstein:Postlingual deafnessandspeechproduction

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(a) H5

3000.

(b) D1 t

ol

I 2000-

i I I

E ErE[ liEE

2000-

I o 7I E •oE 0E

1 n

H

_

UU

e 1500-r

_

U

e 1500-

oUU U

U

z

H

r

U

_ _

aaõ

z

a

_

UøUuø U UaU

U•J

_

udU a

1000--

aa

u

_

.

500

I

6OO

2OO

F1

in

I

400

I

600

8OO

Hertz F1

(c)

D2

in

Hertz

(d)

D3

2500_

i ibiii i

_

2000--

I

2000--

_

I

n n

uo•Ua '• A

H

a

e 1500r

H

U aaøa•

z

e 1500r

U

U

u•u

a z u

a

10001000-

_

_

_ _

500

'

I

'

5OO

200

I

600

F1

In

2OO

'

I

400

.

I

6OO

8OO

Hertz F1

(e)

D4

in

Hertz

{f)

D5

3000 _

2500-_

_

1 _

li

o

.

I

2000•

2000n

U

H

-

UU • øUa

er 1500-

•1 aa

H

aa

r

! EB •EEE 0

e 1500-

o

_

a

UU Uo• U• 0

_

z

z _

u

_

[• u U

u u

500

I 200

I

400

in

(g)

500

I

600

F1

I

8OO

2O0

'

400

6OO

Hertz

F1

D6

(h)

3000 t

2500-•

uU•

1000•

li oii i

in

8OO

Hertz

D7

2500-_

1

I i tbii

_

I

_

1

_

2000•

lz•E z

2000--

1

1

n

I ETT•EE E_

n

o

H

H

e 1500r

er 1500-

z

U •OU U

0 Oaa a

z

u•l uoU

• aa

a

1000-

u

u od Ij

_

_

u

u u

_

_

500 200

'

I

400

'

I

•oo

'

I

800

'

5OO

lOOO

2O0

F1 in Hertz

'

I

400

'

I

•oo

'

I

800

F1 In Hertz

FIG.2.Vowel space plots for(a) subject H5,representative ofthehearing speakers, andfor(b)-(h) each deafened subject. Open circles represent mean values foreachvowel.N.B.:Thesymbol "@" represents thephonetic symbol[ae].

2105

J.Acoust. Soc.Am.,Vol.88,No.5,November 1990

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TABLE III. The F 1 means,standarddeviations,and rangesfor eachsubject.

Subject

Sex

[i ]

[I ]

[ e]

[•e]

[^ ]

H1 H2 H3 H4 H5 H6 H7

F M F F M F F

430 (34) 283 (14) 356 (17) 337 (12) 314 (9) 387 (31) 334 (36)

526 (19) 390 (28) 480 (26) 464 (27) 412 (19) 582 (37) 424 (43)

697 (37) 441 (33) 670 (38) 597 (19) 564 (36) 749 (37) 679 (122)

959 (43) 700(105) 791 (38) 1016 (52) 800(25) 926 (35) 970 (49)

669 (58) 530 (57) 805 (52) 943 (120) 606 (35) 803 (42) 878 (76)

D1 D2 D3 D4 D5 D6 D7

F M F F M F F

361 (40) 286 (13) 344 (24) 477 (54) 358 (29) 416 (33) 406 (32)

671 (119) 361 (47) 469 (27) 588 (56) 499 (28) 519 (38) 568 (37)

871 (83) 355 (39) 595 (48) 664 (33) 615 (32) 569 (52) 627 (42)

865 (69) 379 (38) 626 (20) 825 (74) 696 (16) 706 (50) 810 (38)

717 (218) 347 (34) 619 (29) 745 (52) 627 (32) 725 (69) 717 (50)

differedin age and sex (see Petersonand Barney, 1952)]. The data in these tables show that, overall, the standard de-

viationsfor both F 1 and F 2 valuestend to be largerfor the postlinguallydeafenedgroupthan for the normally hearing group. The magnitudeof the differencebetweenthe two groups,however,is generallygreaterfor the F2 standard deviationcomparisons.Thesedata suggestthat the postlinguallydeafenedspeakersare lessconsistentacrossmultiple repetitionsof a givenvowel in reachingthe acoustictarget specifyingthat vowel. In addition,eachpostlinguallydeafenedsubjectexhibitsrangesfor F 1 and F2 that are smaller than thoseof their hearingcounterparts;as with the standard deviation measures, the differences between the two

speakergroupsare larger in the F 2 comparisons. It is alsoworth noting,on closeinspectionof the vowel

[ a] 919 (71) 702 (71) 854 (52) 1019 (46) 848 (32) 971 (37) 987 (54) 592 (234) 384 (33) 600(14) 768 (44) 683 (29) 860 (143) 879 (31)

[U ]

[u]

Range

(77) (21) (22) (23) (35) (34) (38)

485 (18) 290 (19) 349 (22) 340 (11) 302 (15) 399 (28) 354 (41)

529 419 505 682 546 584 653

686 (80) 309 (14) 485 (14) 647 (59) 504 (52) 585 (15) 619 (48)

404 (68) 305 (8) 353 (16) 480 (34) 367 (31) 470 (64) 458 (52)

510 98 282 348 338 444 523

551 401 516 466 414 603 461

definedloci. There is much overlapof the front vowelsIx e ae], and of the vowels [u a ^]. The greatestdifferencebetween D l's vowel systemand thoseof the normalsis seen, however, in the distribution of the vowels [e a ^]. These vowelsoccupyvery largeranges,and sometokensappearin regionsalongthe F 1 axisnot typicallyseenwhencompared to normals.As a result,the relativeplacementof thesevowelsdiffersfrom normal, and the sequencingof vowelsis out of order.

D2's vowelspace,shownin Fig. 2 (c), issharplyreduced alongboth F 1 and F2 axes.A distinctionbetweenvowels alongthe acuteaxisand vowelsalongthe graveaxisis discernible,but quite small. The vowels [i x e ae^] overlap heavily, and do not follow the sequencenormally seenin hearing subjects'acousticvowel space.The grave vowels [u u a] are relatively discrete,but only Jul has formant frequencyvalueswhich are comparableto normal.

spaceplots,someadditionaldeviations fromthenorm,especiallywith regardto subjects D 1andD2, whoweredeafened at youngerages.Specifically,there appearsto be greater overlapof individualvoweltokensand/or a morerestricted 2. Absolute vowel duration vowel space.SubjectD1, for example,usesmuch of the acousticspace,and there is a generaldistinctionbetween Table V displaysthe absolutevoweldurationsand stanfront and back vowels,but the vowelsdo not occupywelldard deviations for vowels in the context/hVd/, for both

TABLE IV. The F2 means,standarddeviations,andrangesfor eachsubject.

Subject

2106

Sex

[ i]

H1 H2 H3 H4 H5 H6 H7

F M F F M F F

2983 2317 2689 2744 2571 2994 2876

(55) (53) (26) (59) (28) (82) (36)

D1 D2 D3 D4 D5 D6 D7

F M F F M F F

2368 (158) 1934 (32) 2304 (23) 2093 (76) 2203 (40) 2464 (88) 2303 (99)

[I ]

[ e]

[•e]

[^ ]

[ a]

[ U]

[ u]

Range

2336 (92) 1995 (65) 2277 (58) 2135 (38) 2084 (25) 2283 (68) 2348 (60)

2175 (25) 1802 (48) 2033 (54) 2006 (32) 1952 (14) 2231 (65) 2338 (58)

1926 (47) 1619 (28) 1976 (40) 2013 (23) 1836 (17) 2103 (50) 2306 (66)

1882 (49) 1376 (51) 1718 (37) 1635 (99) 1606 (25) 1678 (124) 1617 (157)

1760 (61) 1172 (57) 1281 (52) 1309 (40) 1280 (83) 1402 (52) 1181 (61)

1813 (63) 1146 (82) 1395 (111) 1310 (54) 1424 (118) 1607 (120) 1159 (91)

1376 (121) 914 (33) 884 (57) 1015 (14) 902 (27) 1118 (71) 775 (53)

1607 1403 1805 1729 1669 1876 2101

1947 (66) 1880 (28) 1857 (70) 1933 (51) 1888 (98) 2009 (84) 2021 (69)

1822 (82) 1886 (48) 1728 (53) 1945 (81) 1718 (76) 1992 (38) 1919 (120)

1721 (126) 1962 (41) 1469 (45) 1839 (56) 1490 (74) 1882 (85) 1772 (229)

1283 (156) 1803 (57) 1442 (69) 1740 (56) 1336 (64) 1709 (89) 1718 (121)

1194 (96) 1512 (112) 1124 (37) 1513 (100) 1238 (52) 1350 (122) 1381 (63)

1179 (60) 1643 (121) 1401 (44) 1620 (68) 1345 (175) 1417 (84) 1572 (65)

1042 (58) 972 (64) 1094 (45) 987 (64) 970 (125) 940 (58) 900(95)

1326 990 1210 1106 1233 1524 1403

J. Acoust.Soc. Am., Vol. 88, No. 5, November 1990

Robin S. Waldstein:Postlingualdeafness and speech production

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TABLE V. Mean absolutevoweldurationsand standarddeviationsfor eachsubject.

Subject

[i]

[I]

[œ]

H1 H2 H3 H4 H5 H6 H7

325 (14) 290 (15) 328 (21) 369 (28) 238 (27) 336 (29) 322 (24)

265 (24) 197 (20) 246 (15) 250 (32) 168(9) 224 (34) 169(18)

277 (30) 226 (13) 243 (8) 298 (34) 169(15) 256 (15) 189(10)

•

315 (41.3)

217 (39.6)

D1 D2 D3 D4 D5 D6 D7

346 (92) 271 (21) 446 (33) 385 (63) 324 (22) 476 (37) 455 (30)

•

386 (76.5)

[lle]

[^]

[a]

[U]

[u]

359 (17) 316 (18) 351 (22) 420 (26) 248 (21) 369 (16) 333 (19)

268 (16) 210 (12) 237 (10) 274 (14) 165(16) 253 (19) 152(17)

351 (27) 299 (11) 361 (20) 383 (30) 236 (22) 353 (16) 311 (19)

290 (13) 217 (16) 236 (10) 254 (23) 159(15) 242 (13) 189(10)

263 (72) 265 (10) 350 (24) 319 (24) 224 (16) 321 (33) 245 (14)

237 (46.1)

342 (52.9)

223 (48.8)

328 (49.8)

227 (43.1)

284 (46.3)

239 (96) 223 (19) 346 (30) 223 (32) 207 (26) 337 (50) 262 (22)

297 (72) 247 (15) 403 (45) 381 (26) 247 (31) 352 (38) 263 (32)

235 (37) 236 (30) 489 (24) 405 (62) 418 (48) 458 (34) 480 (53)

306 (62) 183(25) 350 (32) 303 (58) 240 (33) 344 (34) 243 (26)

305 (84) 263 (28) 468 (64) 351 (58) 364 (28) 378 (11) 444 (52)

249 (21) 224 (22) 365 (47) 273 (33) 194(31) 344 (37) 289 (30)

315 (41) 232 (25) 409 (16) 321 (56) 340 (43) 368 (47) 460 (33)

262 (56.7)

313(65.5)

389(109.0)

281 (61.3)

368 (72.1)

277 (61.7)

349 (73.0)

speakergroups.As thetableshows,the overallaverageduration valuesfor the postlinguallydeafenedsubjectstend to be longerwhencomparedto the overallvaluesfor the hearing subjects.Theseresultsare in agreementwith reportsof previousstudies(Binnie et al., 1982;Plant, 1983, 1984). At the sametime, the intrinsicallylongerdurationsobservedin the normals'productionsfor the tensevowels[i ] and [ u ] relative to their lax counterparts[I] and [U] alsoobtainin the postlinguallydeafenedsubjects'data.This durationdistinction, however,asmentionedearlier,doesnot correspondto a phonologicalcontrastin English.The tablerevealsthat the standard deviations of the duration means obtained with the

postlinguallydeafenedsubjectsalsotendto belargerrelative to the standarddeviationvaluesobtainedwith the normally hearingsubjects;this findingindicatesa greaterdegreeof duration variability in the postlinguallydeafenedspeakers' repetitionsof the samevowelsrelative to normal. Thus the

increased average durationanalstandard deviation values appearto be a generaleffectof deafness,while the tense/lax vowel duration distinctionis preserved.

3. Contextually conditioned vowel duration

TableVI presents thevoweldurations for bothsubject groupsasa functionof thevoicingof thefollowingconso-

TABLE VI. Contextuallyconditioned voweldurationsfor normallyhearingandpostlingually deafenedsubjects.

Su•ect H1

H2

H3 H4 H5 H6 H7 D1

D2 D3 D4

D5 D6 D7

2107

[bid] [bit]

[bid ] [bit ]

[bed] [bet]

[ bed] [bet]

[brad] [b•t ]

[bod] [ bot]

[bud] [but]

[b^d] [b^t]

X

289 215 306 220 322 221 436 249 259

236 154 260 194 270 155 316 175 175

317 194 351 249 360 239 460 266 299

259 176 255 208 271 198 327 229 212

419 230 383 262 380 289 485 290 317

299 194 320 220 356 225 448 223 284

269 157 260 201 275 194 318 202 228

307 192 307 226 326 221 408 241 258

177 356 202 333 185

141 257 185 230 162

168 404 221 304 207

157 266 209 244 190

217 435 276 387 274

367 215 319 254 377 250 477 296 293 177 384 252 329 216

156 342 215 357 231

154 275 182 233 188

168 340 218 302 207

333 288 277 248 450 280 355 206 380 181 460 293 474 253

230 157 144 175 357 217 229 149 243 153 327 207 289 199

305 277 252 261 481 290 406 217 338 213 397 279 499 287

181 196 146 183 409 241 259 150 274 175 343 299 317 238

311 305 245 280 480 293 367 205 452 292 436 353 597 356

303 222 249 258 490 292 377 215 393 214 427 382 532 280

322 269 232 240 528 283 398 191 442 195 '" 277 537 272

234 206 178 185 331 226 221 149 303 157 320 273 324 213

277 240 215 229 441 265 327 185 353 198 387 295 446 262

J. Acoust.Soc. Am.,Vol. 88, No. 5, November1990

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nant in the contexts/bVd/and/bVt/.

It has been demon-

stratedthat in English,vowelsprecedingvoicedconsonants are longerin durationthan vowelsprecedingvoiceless consonants(Petersonand Lehiste,1960;Raphael, 1972); moreover,this durationdifferenceis an importantacousticcueto the phonemiccontrastof voicing.The datain TableVI indicate that the majority of subjectsmaintainedthe expected contrastfor all vowels;further, the magnitudeof the distinctionsis comparableto, and sometimes largerthan, that observed in the normals' data. SubjectsD1 and D2 again provedto demonstrateexceptionsto the generalpattern.

Specifically, D 1 maintainedthe durationdistinctionfor the vowels[i e 0eu ^], but the magnitudeof the distinctionsis smallerthan any observedin the normals.A small distinction of a sizewithin the rangeof the normalsis observedfor

mantfrequencies for bothF 1 andF 2 for all speakers. This variabilitysuggests that voweltargetsarelessstablein the postlingually deafened speakers thanin thenormallyhearingspeakers. Thus,in additionto the overallreduction of vowelspacein the postlingually deafenedgroup,in general therewaslessspecificityof individualvowelswithin that space.Nevertheless, vowelsoccurringin theexpected relativelocationsappearedin the vowelspaces of speakers D3D7. The findingthat subjects D3-D7 displayed a relatively well-preserved sequence of vowelsalongthegraveandacute axessuggests that thesespeakers retaina relativelyintact internalrepresentation of vowelspacedespitepostlingual deafnessduring adulthood.

With regardto the durationanalyses, it wasobserved that the majorityof postlingually deafenedsubjects maintained the expected contextually conditioned vowel duration the vowels [I o]; however,a reversalof the contrastis seen (whichprovides animportantacoustic cueto the for the vowel [e], which waslongerprecedingthe voiceless distinction that, onceestabcognatethanwhenit preceded thevoicedcognate.D2 exhib- phonemicvoicingcontrast),suggesting lished,auditoryfeedbackis not requiredto maintainthis its reversalsfor all vowelsexcept[i l, which showsa small phonemiccontrast.Feedbackdoesseemto be required, contrastin the expecteddirection.Thus, while D 1 and D2 as,condisplay very different patterns,neither has consistently however,to fine-tunephoneticdurationproductions sistent with previous reports, the deafened subjects tended to maintainedthe contrastfollowingpostlingualdeafness. showgreaterabsolute voweldurations.Subjects D 1 andD2 4. Discussion wereobserved notto producecontextuallyconditioned vowel durationsin the mannertypicalof the normallyhearing Vowelproduction requiresthatspeakers aimfor acousalthough, aswasfoundwiththevowelformantfretic targets.Theanalyses presented in thisstudyinvestigated subjects, quency analyses, they deviatedin differentwaysfromthe theeffects of postlingual deafness ontheproduction of vownorm. Once again, it is interesting to notethatthesesubjects els.The resultsindicatedthat the vowelsystemsof the posttheirhearinglossat the youngest ages.ThusD 1 linguallydeafened speakers weresomewhat differentfrom acquired and D2 displayed greater deviations in vowel targetingand thoseof the normallyhearingspeakers.All deafenedsubin contextually conditioned voweldurationdifferences, the jectsdisplayeda reductionin theformantfrequencyranges two measures that have linguistic significance, than did the usedin the acousticvowel space.Plant and Hammarberg deafenedspeakers. (1983) reporteda reduction in vowelspacein twoSwedish- otherpostlingually

speaking individuals whoweredeafened at 8 and9 years,but notin a Swedish speaker whowasdeafened at 49 years.The latterresultis surprising, giventheconsistency of therange reductionsin the presentstudy.Reducedrangevaluessuggesta smallerdegree oftonguemovement in articulating the vowels;the currentfindingssuggest that postlingualdeafnessleadsto restrictedtonguemovementin vowelproduction, as has beennoted in the prelinguallydeaf (Monsen, 1974). Thus, whether or not the overall vowel patterning

C. Experiment 3: Suprasegmentals 1. Sentence

durations

Mean sentence durationsfor eachsentence typefor each

subjectgroupcanbe foundin TablesVII andVIII. The normallyhearingspeakers exhibiteddurationvaluesrang-

ingfrom1094-1935 msforthedeclarative sentences, 11412120msfor the yes/noquestions, and 1294to 2293msfor

thewh-questions; duration values forthepostlingually deafenedspeakers rangedfrom1330-2274msforthedeclarative

waspreserved, a smallerrangeof vowelspacewasevidentin thedeafened speakers. Thisfindingsuggests that,evenafter sentences,1415-2330 ms for the yes/no questions,and 1704-2957ms for the wh-questions. Both groupsshowa appropriatevoweltargetshavebeenestablished, adultsapgeneral progression of increasing duration asa function of pearto useauditoryfeedback to maintainthedistinctiveness sentence type, with the smallest values for declaratives and of thesetargets. thelargest forwh-questions; thisresultisexpected sincethe Oneof thefactorscontributingto reducedvowelspaceis declarative sentencescontained the fewest words, while the

thelowerplacementof thevowel[i] alongtheF 2 scalefor wh-questions contained thegreatest numberof words.The all speakers. It is worth mentioning,in thisregard,the hypostlingually deafened speakers, however, tendedto have pothesisthat the vowel [i] holdsa specialstatusin vowel longer durations overall, as compared to their hearingcounperception.Specifically, listenersappearto use [i] as the terparts. Subject D 1, in particular, displays duration values referentagainstwhich they normalizea speaker'svowel whichexceeded thoseof all othersubjects, hearingor deafspace(Nearey,1978).By implication,a deviant[i] might ened. hinderthe speaker'sintelligibilityby makingit more difficult for listenersto performthisnormalizationfunction. 2. Measures of fundamental frequency Furthersupportfor theproposalthatauditoryfeedback a. Mean FO and FO standard deviations. Tables VII and functionsto monitor the precisionof vowel targetsinto VIII alsodisplaymeanF0 valuesand meanF0 standard adulthoodliesin the findingof increased variabilityof for2108

J. Acoust.Soc.Am.,Vol.88, No.5, November 1990

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TABLE VII. Suprasegmental measures for normallyhearingsubjects. F0

Sentence

Subjecttype H1

H2

H3

H4

H5

H6

H7

Sex

D Y/N WH

F

D Y/N WH

M

D Y/N WH

F

D Y/N WH

F

D Y/N WH

M

D Y/N WH

F

D Y/N WH

F

X F0

X s.d.

X F0-min

X F0-max

Y/N

terminal

Range

rise

X duration (ms)

246.8 (7.6) 246.2 (6.8) 248.1 (5.2)

9.3(3.3) 10.7 (2.7) 9.5 ( 1.3)

228.0 (2.9) 225.5 (8.9) 231.3 (7.3)

265.5 (11.0) 279.8 (13.8) 267.8 (6.1)

37.5 54.3 36.5

yes

1506.8 (93.2) 1558.0 (123.3) 1706.5 (134.2)

131.0 (4.7) 140.3 (6.0) 134.0 (5.7)

20.9 (2.3) 14.3 (1.2) 29.5 (2.3)

84.8 (3.0) 112.3 (6.2) 96.0 (7.1)

175.0 (2.2) 169.8 (3.6) 194.3 (16.6)

90.2 57.5 97.7

yes

1935.8 (190.5) 2120.5 (178.6) 2293.8 (162.6)

170.4 (5.8) 179.5 (7.4) 178.0(11.3)

17.3 (4.4) 14.6 (4.5) 22.5 (5.0)

128.8 (28.7) 146.3 (3.4) 123.0(12.9)

208.5 (11.3) 223.8 (24.7) 225.3 (14.7)

79.7 77.5 102.3

yes

1416.8 (185.7) 1503.5 (196.7) 1759.5 (89.1)

173.7 (8.6) 192.2 (15.7) 182.2 (4.9)

15.8 (2.5) 13.1 (3.4) 22.1 (1.6)

141.5 (7.9) 169.8 (8.0) 142.8 (6.7)

198.5 (15.2) 228.8 (25.2) 232.5 (8.5)

57.0 59.0 89.7

yes

1412.8 (125.9) 1398.0 ( 171.0) 1580.3 (127.6)

110.0 (5.8) 116.0 (7.4) 124.3 (11.4)

8.4 (2.5) 10.3 (3.4) 11.8 (4.5)

93.5 (2.4) 100.5 (5.3) 93.3 (6.4)

125.0 (10.1) 143.0 (18.0) 142.8 (14.1)

31.5 42.5 49.5

yes

1094.0 (117.0) 1141.8 (91.6) 1294.5 (68.6)

214.4 (5.9) 222.5 (6.6) 213.6 (3.8)

28.1 (6.7) 16.3 (2.2) 36.1 (3.7)

142.2 (12.8) 182.3 (4.3) 133.0 (12.8)

256.5 (18.5) 257.0 (12.3) 300.0 (9.5)

114.3 74.7 167.0

yes

1451.0 (161.3) 1510.8 (78.5) 1741.5 (89.1)

169.3 (12.0) 191.3 (19.4) 197.1 (40.0)

25.3 (7.1) 34.4 (6.1) 38.3 (12.6)

134.8 (13.3) 136.3 (12.3) 148.8 (32.9)

230.5 (27.8) 274.8 (30.6) 287.5 (31.1)

95.7 138.5 138.7

yes

1323.3 (160.8) 1433.8 (155.5) 1545.0 (214.6)

deviationvaluesfor each speakergroup. Table VII shows that the meanF0 valuesfor the normallyhearingsubjects rangebetween110 and 248 Hz. The two male subjects,H2 and H5, display the lowest averageF0 values, ranging between110 and 140 Hz, and subjectH 1, a femaleaged 13, displaysthe highestaverageF0 values,rangingbetween246 and 248 Hz. The averageF0 valuesfor subjectsH3, H4, H6,

withvaluesrangingbetween169and222Hz. Thisprogres-

and H7, all adult females, fall inbetween these two extremes,

youngest subject, D1, shows thehighest meanF0 values.

sionis consistentwith normativevaluesofF0 with respectto

ageandsex(e.g.,Kent, 1976).

Thepostlingually deafened speakers' average F 0 values, shownin TableVIII, conformroughlyto the patterndis-

played bythehearing subjects; thatis,themalesubjects, D2 andD5, fall at the lowerendof the continuum, whilethe

TABLE VIII. Suprasegmental measures for postlinguallydeafenedsubjects. Sentence

Subjecttype D1

D2

D3

D4

D5

D6

D7

2109

F0

Sex

D Y/N WH

F

D Y/N WH

M

D Y/N WH

F

D Y/N WH

F

D Y/N WH

M

D Y/N WH

F

D Y/N WH

F

X F0

X s.d.

Y/N

terminal

X F0-min

X F0-max

Range

rise

X duration (ms)

343.9 (9.8) 356.8 (11.9) 355.4 (4.7)

16.0 (3.1) 23.9 (2.6) 26.4 (5.7)

300.8 (15.8) 296.8 (6.1) 295.5 (5.2)

377.5 (12.3) 411.8 (5.7) 420.5 (15.9)

76.7 115.0 125.0

no

2274.3 (288.9) 2330.0 (211.5) 2957.0 (414.6)

127.9 (5.0) 130.1 (4.6) 127.5 (1.2)

10.2 (3.4) 10.2 (2.9) 10.4 (0.9)

112.3 (2.9) 111.0 (2.7) 111.0 (1.4)

151.5 (14.9) 153.3 (11.8) 153.5 (3.9)

39.2 42.3 42.5

no

1405.8 (193.3) 1566.3 (221.6) 1740.5 (210.9)

137.0 (6.0) 163.1 (7.4) 140.0 (5.1)

11.1 (3.0) 10.5 (0.4) 12.5 (1.7)

115.0 (8.4) 144.0 (7.1) 114.5 (7.1)

163.3 (13.8) 192.5 (16.6) 169.5 (7.9)

48.3 48.5 55.0

no

1727.8 (238.5) 1740.5 (236.2) 2171.3 (205.7)

193.1(22.5) 200.8 (19.0) 204.2 (11.2)

24.1 (3.5) 27.9 (8.3) 22.0 (4.5)

139.3 (26.6) 154.0 (18.6) 143.8 (11.9)

233.8 (26.6)

94.5

250.8 (16.9) 244.3 (17.1)

96.8 100.5

yes

1330.5 (135.7) 1415.3 (42.6) 1704.3 (65.0)

157.2 (13.6) 162.3 (7.4) 163.1 (3.4)

9.9 (6.9) 9.5 (4.0) 13.2 (2.7)

133.0 (0) 136.3 (5.4) 131.0 (9.9)

172.5 (23.3) 182.5 (16.3) 187.3 (8.0)

39.5 46.2

223.9 (6.2) 247.1 (16.4) 246.3 (6.9)

25.5 (2.9) 21.3 (6.7) 38.4 (11.6)

162.0 (22.1) 205.3 (6.3) 174.0 (20.8)

265.5 (8.7)

103.5

316.0 (40.4)

110.7

333.0 (43.1)

159.0

182.2 (6.3) 235.1 (43.3) 197.4 (22.8)

25.7 (6.3) 47.5 (21.2) 54.1 (6.3)

130.8 (14.0) 141.3 (3.9) 124.0 (18.1)

242.0 (24.4)

111.2

336.5 (87.5)

195.2

324.5 (51.7)

200.5

J. Acoust.Soc.Am.,Vol.88, No.5, November 1990

yes

56.3

1947.0 (369.1) 2055.8 (407.2) 2276.3 (178.9)

1642.5 (258.6)

yes

1853.5 (331.2) 2151.8 (180.2)

2008.0 ( 301.4)

yes

1892.5 (230.0) 2156.3 (229.0)

RobinS. Waldstein: Postlingual deafness andspeechproduction

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Althoughabsolute differences existbetween thespeakers indicatinghigheroverallF0 valuesfor thepostlingually deafenedspeakers, thedifferences aresmallenoughto beattributed to normalvariation.Moreover,the largestdifference canbeattributedto theF0 valuesof subjectD 1,whosemean

400

• -

_

F0 values(rangingbetween343 and 356 Hz) exceednot

30O -_

onlytherangeof valuesfoundin thehearingsubjects in this studybut alsothe normsfor 6-year-olds(the ageat which D 1 becamedeaf),aswellasaverage F0 valuesreportedfor

-

-

-

200

-_

.

adolescentfemales(Kent, 1976). Binnieet al. (1982) also observedvery high mean F0 valuesof around400 Hz in a

-

.

_

childduringthe9 monthsfollowing a sudden hearing lossat theageof 5. To sumup,theredoesnotseemtobea straight-

.

-

.

o

forwardeffectof postlingualdeafness on meanF0.

Similarly,theF0 standarddeviationvaluesdo not appearto consistently differentiate the deafenedsubjects from thehearingsubjects. Thismeasure calculates thedegreeof scatterof all F0 pointsin the contouraboutthe mean,and thusreflectsthedegreeofF0 variabilitywithintheutterance.

see

75e

leee

1•5e

1see

17•O

Ms FIG. 3. Yes/no questionintonationcontourfor "Did thedogrun outside?," spokenby subjectD7, exhibitingwide F0 excursions.

TheF0 standard deviation valuesfor thenormallyhearing speakersrangedfrom 9-38 Hz, while the F0 standarddevi-

Takentogether,theF0 maxima,minima,andrangeval-

ationvaluesfor thepostlingually deafened subjects ranged uessuggestthat the deafenedspeakers'rangesof fundamenfrom9-54 Hz. The slightlyhigherrangefoundin the deaf- tal frequencyproductionwere roughlycomparableto the enedsubjects'groupcanbe attributedto subjectD7 alone, who showedthe highestF0 standarddeviationvaluesof all

subjects, deafened or hearing,for the yes/noquestion and wh-question tokens.Thus,in general,controlof F0 across sentence-length utterances, asdemonstrated by thepostlinguallydeafenedsubjects in this study,wascomparable in variabilityto that of thenormallyhearingsubjects. b. FO minima, maxima, and range.Calculationsof F0 minima,maxima,and rangevaluesprovideanotherassessment ofF0 control;thesemeasuresconstitutean indexof the excursions reachedin a givenutterance.An examinationof

TableVII revealsthat the F0 rangevalues,computedby subtractingthe F0 minima valuesfrom the F0 maxima valuesfor each subject,varied between31 and 167 Hz for the

normally hearing subjects.The postlinguallydeafened speakers' F0 rangevalues,asshownin TableVIII, arevery similarto thoseof thehearingsubjects; in particular,theF0 rangevaluesfor thepostlingually deafenedsubjects fellwithin therangeofvaluesobserved in thehearinggroup,withthe exception of subjectD7'srangesfortheyes/noquestion and wh-question categories. TheF0 minima,asshownin TableVII, rangedbetween 84 and231 Hz for the normallyhearingspeakers, whereas F0 maximavaluesfor thehearingsubjects rangedbetween 125and300Hz. TableVIII suggests that,onbalance,theF0 minimaand maximavaluesfor the postlingually deafened speakers fell withinthe valuesobserved in the hearingsubjects'data,with theexceptionof speakerD 1,whodisplayed higherF0 minima and maxima in all three sentencecondi-

tions.SpeakersD6 and D7, however,displayedhigherF0 maximain someproductionsof yes/no questionsthan were seenin the normallyheatingsubjects. Figure3 presentsan exampleof one of theseproductions.This resultindicates that somepostlingually deafenedsubjects wereoccasionally lessprecisein controllingF0 excursions in theproductionof yes/no questions. 2110

J. Acoust.Soc. Am.,Vol. 88, No. 5, November1990

valuesof the normallyhearingspeakers. c. Directionof terminal. The terminal portion of an F0 contourhasbeenidentifiedasan importantlinguisticcueto the phrasestructureof an utterance(e.g., Lieberman,1967). Thus a declarativesentencegenerallyendswith a falling terminal, whereasa yes/no questiongenerallyhasa risingterminal. An examinationof the normally hearingspeakers' intonationcontoursfor declarativesentences, yes/no questions,and wh-questionsrevealedthat all speakersexhibited a terminal fall in their productionof declaratives,and a terminal risein their productionof yes/noquestions.Wh-question contourswere most often characterizedby a terminal fall, although sometokens exhibitinga terminal rise were noted.The critical linguisticcontrast,however,is the presenceor absenceof a terminal risein the productionof yes/no questions.Given that the terminal directionis linguistically determined,it wasof interestto determinewhetherthe postlingually deafenedsubjectsexhibitedthe appropriatepatterns.All of the deafenedspeakersshowedterminalfalls in their production of declarativesentences.With respectto the presenceor absenceof a terminalrisein the productionof yes/no questions,however, Table VIII indicatesthat subjects D4-D7 exhibitedterminal risesin the productionof yes/no questions;in contrast,subjectsD l-D3 producedterminal fallsfor this questiontype. Again, thesesubjectswere deafenedat the youngestagesin the group. $. Fundamental frequency jitter

It hasbeendemonstrated thatfineF0 controlisquickly affectedby auditoryfeedbackmanipulationwith normally hearingspeakers(e.g., Elliott and Niemoeller, 1970). Anothermeansof assessing fineF0 controlis to obtaina measureof theamountof F0 jitter, or period-to-period variability.

Table IX showsthe amountof jitter for both speaker RobinS. Waldstein:Postlingual deafnessand speechproduction

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this areacouldhelpto resolvethe dissimilarities amongthe

TABLE IX. Period-to-periodvariabilityfor eachsubject.

results of these studies. Subject H1

Mean

Subject

Mean

0.057

D1

0.027

H2

0.045

D2

0.029

H3

0.053

D3

0.034

H4

0.067

D4

0.040

H5

0.062

D5

0.028

H6

0.048

D6

0.037

H7

0.060

D7

0.045

groups.Jitter wasdefinedas the standarddeviationof the period-to-perioddurations,normalizedwith respectto F0, following Lieberman (1961, 1963;seealso Ryalls, 1984). The values for the hearing subjectsranged between0.045 and 0.067, whereasthose for the postlinguallydeafened rangedbetween0.027 and 0.045. In all cases,the deafened subjects'valueswere smaller than those of their hearing counterparts,suggesting that the deafenedsubjectsdiffered

from the hearingsubjectsin fine phonatorycontrol.While the underlyingreasonfor this findingis at presentnot clear, decreased jitter appearsto be a generaleffectof postlingual

The F0 measures describedabovedo not reflectlinguistically meaningfulcontrastsper se. However,the useof a terminalrisein F0 duringyes/noquestionproductiondoes providea linguisticallysalientcue.The resultsof the analysesexaminingterminal rise suggestpotential deficitsas a functionof the ageat which the postlinguallydeafenedsubjectshad acquiredtheir hearinglosses.Specifically,subjects D l-D3, who were deafenedat earlier ages,showedfalling yes/no intonation contours, while subjectsD4-D7, who weredeafenedin adulthood,showedrisingF0 contoursfor yes/no questions.Somespeakersin the latter group, however,exhibitedhigherF0 maximain someyes/noquestion intonationcontoursthan wereseenin the normals'productions.Thuspostlingualdeafness later in life may not resultin a lossof the terminalrise/fall distinction;thissuggests that the productionof linguisticallydeterminedintonationcontoursisinternalizedin adults,althoughprecisecontrolofF0 excursionsmay be subjectto auditoryfeedbackmonitoring. III. GENERAL

DISCUSSION

AND CONCLUSIONS

The experimentsin this investigationwere designedto characterizethe effectsof a postlinguallyacquired, total hearinglosson speechsoundproduction.Spectraland tem4. Discussion poralpropertiesof consonants, vowels,andsuprasegmentals Productionof the suprasegmental properties of speech in the speechof sevenpostlinguallydeafenedindividuals is traditionallythoughtto be controlledby auditoryfeed- were comparedto age-matchednormals in order to deter-

deafness.

back.The presentanalysisexploreda varietyof supraseg- mine whether there were differential effects of a loss of audimentalparametersin the speechof postlinguallydeafened tory feedback,or whether there was an across-the-boardefindividualsin an attemptto evaluatethisclaim.The results suggestedeffectsof postlingualdeafnesson severalof the suprasegmental measures obtained.Specifically, thepostlinguallydeafened subjects tendedto showlongersentence durationsascompared to thenormallyhearingspeakers. Similar resultshave been previouslyreportedfor sentences (Leder et al., 1987c) and for words (Binnie et al., 1982; Plant, 1983;Plant and Hammarberg,1983;Zimmermann

fect on thesesoundproperties. The resultsof the presentstudy found phoneticdeviationsin the speechof the postlinguallydeafenedindividuals in each speechclassstudied,i.e., consonants,vowels,and suprasegmentals. Thusthe datado not supportthe hypothesis that the suprasegmental propertiesof speechshow the greatesteffectsof a lossof auditoryfeedback,while the segmental propertiesremain relatively unaffected.Rather, auandRettaliata,1981). In addition,all of thedeafened speak- ditory feedbackappearsto be implicatedin monitoringand ersshoweda smalleramountof F0 jitter relativeto normal. maintaining phonetic precision in all classesof speech The presentstudy, then, confirmsthat increasedduration sounds. While phonological distinctions were generally andchangesin phonationare by-products of a lossof audi- maintainedby the majority of postlinguallydeafenedspeaktory feedback,andsuggests that auditoryfeedbackservesto ersin thisstudy,their executionwaslessprecise.The results regulatetheseparameters. thus substantiatethe hypothesisthat normally hearing The measures of meanF0, F0 standarddeviation,and speakersuse auditory feedbackin speechmaintenanceto F0 minima, maxima,and rangevaluesdid not showclear calibratethe fine phoneticadjustmentsrequiredto produce differences betweenthe two speakergroupsin this study. high-qualityspeech(e.g., Gammon et al., 1971). The data Consistentwith these results,Plant and Hammarberg are consistentwith the claim that the speechproductionsys(1983), whostudiedthreepostlingually deafened speakers, tem is under someform of closed-loopfeedbackcontrol, as also reportedno differencesin mean F0 betweentheir subsuggestedby Elman (1981), Zimmermann and Rettaliata jectsandnormallyhearingspeakers, but did observesome- ( 1981 ), and Lane (1988). what smaller F 0 standard deviation measuresrelative to norIt is usefulto comparethe resultsof auditory feedback of a mal.In contrast,Lederetal. (1987a)reportedhighermean manipulationstudies,which reflectthe consequences F0 valuesin a largergroupof postlingually deafened speak- short-termdeprivationof auditoryfeedback,to the resultsof ersrelativeto normals.It isnotclearat presenthowto recon- the presentstudy, which addressedthe effectsof auditory ciletheseresults. Asisthecasewithprelingually deafspeak- feedbackdeprivationover the long term (focusingfor the momentonly on the effectsof postlingualdeafness acquired ers (e.g., OsbergerandMcGarr, 1983), it may bethat there in adulthood).The feedbackmanipulationstudieswith noris a gooddeal of individualvariabilityin measuresof F0 mally hearingsubjectshaveshownnumerouschangesin suamongpostlinguallydeaf speakers.Further researchinto 2111

J. Acoust.Soc. Am., Vol. 88, No. 5, November1990

RobinS• Waldstein:Postlingualdeafnessand speechproduction

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prasegmentalproduction,includingimmediatechangesin fineF 0 control (Elliott and Niemoeller, 1970;Mallard, Ringel, and Horii, 1978;Ward and Burns, 1978;Ternstromet al., 1988), an increasein utteranceduration (e.g., Ringel and Steer, 1963;Ladefoged,1967;Mallard et al., 1978), and greatervariabilityin F 0 maximaduringsentence production (Mallard et al., 1978). The currentexperiments alsoshowed changesin fineF0 control (measuredby amountof F0 jitter), absolutevoweland sentenceelongation,andmorevariabilityin F0 maximaduringsentenceproductionin the postlingually deafenedsubjects'speech.Consideredtogether, theseresultsstronglysuggestthat the above-mentionedsuprasegmentalparameters,which are not linguisticallyrulegoverned,are regulatedby auditoryfeedback.On the other hand, the productionof stressdifferences(Gammon et al., 1971) aswell asa terminal risein yes/noquestions(Mallard et al., 1978) have been shownto be relatively preservedin normally hearingspeakersdespitethe presenceof masking noise,aswasthe productionof terminal risein the speechof the postlinguallydeafenedspeakersin this studywho were deafenedin adulthood.Theseresultssuggest that in contrast to lower levelaspectsof suprasegmental production,higher level, rule-governedsuprasegmental processes may not rely on moment-to-momentauditory feedbackmonitoring. Vowel quality has receivedlesssystematicattention in feedbackmanipulationstudies.Kelso and Tuller ( 1983) report accuratevowel targetingin normally hearingspeakers under maskingconditions.In addition, evidencefrom bite blockstudiesin which the formantfrequencies of vowelsare measuredat the first glottal pulseindicatesaccuratetargeting without the benefitof auditoryfeedback(e.g., Lindblom and Sundberg,1971). The datapresentedin thisstudy,however,showeda declinein precisionin the prototypicalvowel space,with greatervariability in formant frequencyvalues, as well as an overall reductionin the rangeof thesevalues followinga long-standinglossof auditoryfeedback.It is possiblethat suchphoneticchangesoccuror developgradually followingpostlingualdeafness. Further researchisneededto determinethe reasonfor this discrepancy. Finally, consonantproductionis typicallythoughtto be under the primary regulationof tactile and/or proprioceptive feedback(e.g., Ladefoged,1967;Gammonet al., 1971). Nevertheless,disturbancesin consonantproductionunder maskingconditionshavebeennotedin an articulatory kinematic study of bilabial closure (McClean, 1977), as well as

in an acousticanalysisof the productionof the voicingfeature in stop consonants(Crary et al., 1979). The resultsof the presentstudyalsoindicatedlessprecisionin the tempo-

ral parameterof voice-onsettime in stop consonantsin speakerswith a long-termpostlingualhearingloss.Considered together,thesedata suggestthat auditory feedbackis indeedusedto regulatephoneticprecisionduringconsonant production.It wouldbe interestingto exploreother aspects of consonant productionin the speechof postlingually deafenedsubjects,as well as in hearingsubjectswhile speaking under masking conditions.For instance,nasal consonant productionalsoinvolvesa timingrelationshipbetweenvelar movement

and release of the oral closure. Would

a similar

effectof reducedprecisionbe found in the productionof 2112

J. Acoust. Soc. Am., Vol. 88, No. 5, November 1990

nasal consonantsin the absence of auditory feedback? Further, would a relativelystaticacousticproperty,suchas placeof articulation,be relativelysparedin comparisonto the changesobservedin VOT, a featureinvolvingcomplex coordinationof two distinctarticulatorygestures? Another interestingobservationthat emergedin this study,but that remainssomewhatspeculative,concernsthe patterningof resultswith respectto ageat onsetof postlingual deafness.Specifically,the speakerswho becamedeaf earlierin life oftendeviatedfrom thenorm to a greaterextent than did the subjectswho becamedeaf at later ageson measures of both segmentaland suprasegmentalproperties; further, thesedifferencessometimescompromisedphonologicalintegrity.The speakerswhosehearinglosses wereacquired at later ages,on the other hand, tendedto display primarily phonetic deviations;in general, these speakers demonstrateda relative preservationof phonologicalcontrasts,but they did so with lessphonetic precision.These findingswereobservedin analysesof both spectraland temporal parametersin the postlinguallydeafenedspeakers' productions.Thusthe linguisticdistinctionsanalyzedin this studywereoftenshownto be vulnerableto greaterchangein the productionsof speakerswhosehearingwaslostat earlier ages,duringchildhood.Additional supportfor thishypothesiscomesfrom an acousticstudyof both segmentaland suprasegmentalspeechparametersin three Swedish-speaking individualswho differedaccordingto the ageat which they becamedeaf:an 18-year-oldfemaledeafenedat age8, an 18year-oldmaledeafenedat age9, anda 59-year-oldmaledeafenedat age 49 (Plant and Hammarberg, 1983). Note that the variable of number of yearspost-onsetwas controlled for; all speakershad beendeaf for approximately10 years. The speakerswho were deafenedat ages8 and 9 displayed restrictedF0 rangesdespiterelativelynormal meanF0 values;in addition,thesesubjectsfailed to demonstratea risein F0 signalingemphaticstress.With regardto vowelproduction, reducedvowel spaceand much overlapin long/short vowel duration distributions were evident. In contrast, the

speakerwhowasdeafenedat age49 displayedgreaterpreservation of all parameters,includingthe use of F0 to signal emphaticstress. It shouldbenotedthat the speechpatternsof the speakers who were deafenedat the youngestagesin the present studywere oftenvery differentfrom oneanother,especially with regardto the segmentalmeasures.A similar resultwas reportedby Plant and Hammarberg( 1983). Thusit appears that a postlinguallossof hearingoccurringduringchildhood may not necessarilyresult in consistentspeechpatterns within a group;rather,the data suggestthat individualchildren may differ with respectto the age at which they fully establishan internal representationof the phonological propertiesof language.This is in keepingwith the common observationin the literature on speechsoundacquisition that normallyhearingchildrentypicallydisplayindividual differences in rate of phonologicaldevelopment(e.g., Zlatin and Koenigsknecht,1976; Allen and Hawkins, 1980; Ingram et al., 1980). Finally, thevariableof lengthof time sinceonsetof deafnesswasnot controlledin the currentstudy.It isunknownat

Robin S. Waldstein: Postlingualdeafness and speech production

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7, 335-342. presentpreciselyhowthisfactorcontributesto the observed Elliott, L. L., andNiemoeller,A. F. (1970). "The roleof hearingin controleffectsofpostlingualdeafness onspeech.Binnieetal. (1982) ling voicefundamentalfrequency,"Int. Audiol. 9, 47-52. observedgradualchangesin the speechof a child duringthe Elman, J. (1981). "Effectsof frequency-shifted feedbackon the pitch of ninemonthsfollowingsudden,total deafnessat the ageof 5. vocal productions,"J. Acoust. Soc.Am. 70, 45-50. Similarly, Plant (1984) noted a declinein suprasegmental Gammon, S., Smith, P., Daniloff, R., and Kim, C. (1971). "Articulation and stress/junctureproductionunder oral anesthetizationand maskqualityratingsof an adolescent's speechsamplesobtained2 ing," J. SpeechHear. Res. 14, 271-282. monthsand 30 monthspost-onsetof a postlingualhearing Ingram, D., Christensen,L., Veach, S., and Webster,B. (1980). "The aclossat the ageof 11.On the otherhand,Lederand colleagues quisitionof word-initial fricativesand affricatesin Englishby children between2 and 6 years,"in Child Phonology,editedby G. Yeni-Komshian (1987a,b,c) failedto find significantdifferencesin measures and J. Kavanagh (Academic,New York). ofsententialF0, amplitude,or durationbetweenpostlingualKelso,J. A. S., andTuller, B. (1983)." 'Compensatory articulation'under ly deafenedspeakerswho hadbeendeaffor lessthan 10years conditionsof reducedafferentinformation: a dynamic formulation," J. relativeto thosewho had beendeaf for more than 10 years. SpeechHear. Res. 26, 217-224. Additional studies tracking the time course of speech Kent, R. (1976). "Anatomical and neuromuscular maturation of the speechmechanism: evidencefrom acousticstudies,"J. SpeechHear. Res. changesfollowing postlingualdeafnesscould clarify this 19, 421-447. question.The patterningof resultsin the presentdata, howKewley-Port,D., andPreston,M. S. (1974). "Early apicalstopproduction: ever,suggestthat ageat onsetof deafnessmay outweighthe a voiceonsettime analysis,"J. Phon. 2, 195-219. Ladefoged,P. (1967). ThreeAreasof ExperimentalPhonetics(Oxford U. factorof lengthof time sinceonsetof deafnessasa significant P., London). influenceon speechconservationover the long term. Lane, H. (1988). "Speechdeteriorationin postlinguallydeafenedadults," In conclusion,the overall resultsof this study demonunpublishedmanuscript. Lane,H., andTranel, B. (1971). "The Lombardsignandthe roleof hearing strate that postlingualdeafnesshas an across-the-boardefin speech,"J. SpeechHear. Res. 14, 677-709. fect on speechsoundproperties,involvingaspectsof consoLeder, S. B., Spitzer,J. B., and Kirchner, J. C. (1987a). "Speakingfundanant, vowel, and suprasegmental production.In addition, mental frequencyof postlinguallyprofoundlydeaf adult men," Ann. the resultsare suggestive of effectsof ageat onsetof deafness; Otol., Rhinol. Laryngol. 96, 322-324. specifically,the speakersin thisstudywho werepostlingual- Leder, S. B., Spitzer,J. B., Milner, P., Flevaris-Phillips,C., Kirchner, J. C., and Richardson,F. (1987b). "Voice intensityof prospectivecochlear ly deafenedin childhooddisplayeddeviationsin speechpatimplant candidatesand normal hearingadult males,"Laryngoscope97, terning that often compromisedphonological integrity, 224-227. whereasspeakerswho weredeafenedin adulthooddisplayed Leder,S. B., Spitzer,J. B., Kirchner,J. C., Flevaris-Phillips,C., Milner, P., and Richardson,F. (1987c). "Speakingrate of adventitiouslydeaf male primarily phoneticdeviations.Thus the resultsare consiscochlearimplant candidates,"J. Acoust. Soc.Am. 82, 843-846. tent with the hypothesisthat auditoryfeedbackcontinuesto Lieberman,P. (1961). "Perturbationsin vocalpitch," J. Acoust.Soc.Am. play a major role in the acquisitionof speechskillsduring 33, 344-355. childhood,and, further, that it functionsto maintain phoLieberman,P. (1963). "Someacousticmeasuresof the fundamentalperiodicityof normaland pathologiclarynges,"J. Acoust.Soc.Am. 35, 344neticaccuracyduringskilledspeechin adulthood. 353.

ACKNOWLEDGMENTS

This article is based on a thesis submitted to Brown Uni-

versity in May, 1989 in partial fulfillment of the requirementsfor the doctoraldegreein Linguistics.The authorgratefully acknowledgesthe guidance of Sheila Blumstein, Philip Lieberman, and Arthur Boothroyd, all of whom servedas dissertationadvisors.Many thanks are also extended to Shari Baum, John Folkins, Randall Monsen, and

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