Efficacy of the Discreteness of Voicing Category (DOVC) Measure

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Efficacy of the Discreteness of Voicing
Category (DOVC) Measure for
Characterizing Voicing Errors in Children
With Cochlear Implants: A Report

Sneha V. Bharadwaj
Amanda G. Graves
Purpose: This investigation explored the utility of an acoustic measure, called the
Callier Center, University of Texas at Dallas
discreteness of voicing category ( DOVC), in identifying voicing errors in stop
consonants produced by children with cochlear implants. Another objective was to
examine the perceptual relevance of the DOVC measure and 2 commonly used
voice onset time ( VOT )-based measures, namely, mean VOT and DVOT (e.g., VOT
/t/ – VOT /d/).
Method: Phonetic transcription and acoustic analyses were carried out on syllable–
initial /t/ and /d/ produced by 10 children with cochlear implants. The DOVC
was calculated as the difference between the shortest VOT value of a voiceless stop and
the longest VOT value of a voiced stop across several productions of each.
Results: Phonetic transcription revealed that 4 of the 10 talkers demonstrated atypical
voicing distinctions. Acoustic analyses indicated that the DOVC measure identified
these same 4 talkers as producing atypical values, whereas mean VOT and DVOT
identified a different set of talkers as demonstrating values outside the normal ranges.
Conclusion: Preliminary findings suggest that the DOVC measure corresponded with
perceptual data better than the other acoustic measures examined in the present study.
Data indicate that the DOVC measure may provide perceptually relevant information
concerning the production of voicing distinctions.
KEY WORDS: children, cochlear implants, voice onset time, production, acoustic

V oice onset time (VOT) is the duration between the release of a com-
plete articulatory constriction and the onset of phonation (Lisker
& Abramson, 1964). VOT is typically used to classify productions
associated with voiced and voiceless stop consonants in syllable–initial
position. Production of accurate voicing distinctions is assessed using both
perceptual and acoustic measures. The perceptual measures include pho-
netic transcription and judgments from voicing identification experiments.
Some of the acoustic measures include mean VOT duration, VOT range,
DVOT (mean voiceless VOT – mean voiced VOT), first formant frequency
cutback, burst amplitude, and vowel duration (e.g., Forrest & Rockman,
1988; Jiang, Chen, & Alwan, 2006; Lisker & Abramson, 1964; Monsen,
1976; Ryalls & Larouche, 1992; Wambaugh, West, & Doyle, 1997).
Accurate production of voicing distinctions is impacted by hearing
loss. For instance, through acoustic analysis, Monsen (1976) showed that
more than half of the children with profound deafness between the ages of
11 and 16 years, who used hearing aids, did not produce voiceless versus
voiced distinctions, whereas all their age-matched controls demonstrated

Journal of Speech, Language, and Hearing Research • Vol. 51 • 629–635 • June 2008 • D American Speech-Language-Hearing Association 629
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accurate voicing distinctions. Further, Waldstein (1990) and Liker (2006), acoustic analysis did not reveal any
compared the production of voicing contrasts by indi- group difference in VOT values in children using cochlear
viduals who had experienced hearing loss either during implants versus hearing aids. However, listeners judged
childhood (prelingually deafened) or as adults (post- voicing production in children with cochlear implants to
lingually deafened). Compared with individuals with nor- be better than in children with hearing aids. Thus, there
mal hearing, the adults who were postlingually deafened is an indication in the literature that some VOT-based
demonstrated shortened VOT values for voiceless con- acoustic measures may not correspond well with percep-
sonants. Similarly, the adults who were prelingually tual judgments of the production of voicing distinctions
deafened demonstrated shortened VOT values along (see Forrest & Rockman, 1988, for a review). Therefore,
with other types of voicing errors, including a greater de- one of the main objectives of the present study was to
gree of prevoicing and overlapping VOT distributions. identify a VOT-based acoustic measure that corresponds
This finding suggests that the onset of deafness at youn- with trained listeners’ judgments of voicing distinctions.
ger ages is particularly detrimental to accurate produc- In the present study, we evaluated the efficacy of an
tion of voicing distinctions. acoustic measure, called the discreteness of voicing cat-
Cochlear implantation in children with severe– egory ( DOVC), in identifying voicing errors in children
profound deafness has led to substantial short- and with cochlear implants. The DOVC measure represents
long-term improvement in the production of voicing the difference between the shortest VOT value of a voice-
distinctions (see Economou, Tartter, Chute, & Hellman, less stop and the longest VOT value of a voiced stop across
1992; Higgins, McCleary, Carney, & Schulte, 2003; several productions of each. In a study of the development
Lane, Wozniak, Matthies, Svirsky, & Perkell, 1995). In of the voicing contrast, Zlatin and Koenigsknecht (1976)
a study of 8- to 9-year-old users of cochlear implants, showed a substantial overlap in VOT distributions of
Uchanski and Geers (2003) showed mean VOT values, 2-year-old children (negative DOVC values), only a min-
VOT range, and average DVOT (VOT /t/ – /d/) to be within imal overlap in the distributions of 6-year-old children,
normal limits in 84%–88% of talkers enrolled in oral com- and no overlap (positive DOVC values) in the distribu-
munication programs compared with 62%–79% of talkers tions of voiced and voiceless stop consonants produced
enrolled in total communication programs. Although by adults. Thus, the DOVC measure has been used to
these findings are encouraging, it appears that accurate quantify the degree of overlap or separation in the VOT
production of voiced and voiceless consonants continues distributions (Zlatin & Koenigsknecht, 1976). Because
to be difficult for a subset of children with cochlear im- the DOVC measure reflects the degree of overlap be-
plants. Another recent study that examined the produc- tween the distributions of voiceless and voiced stops and
tion of voicing distinctions in pediatric users of cochlear takes into account the extreme values in the distributions,
implants versus hearing aids showed comparable mean it was hypothesized that this measure would be closely
VOT values for both groups. However, the findings in- related to trained listeners’ judgments concerning the
dicate that neither group differentiated voiced versus production of voicing distinctions. Because the measure
voiceless categories in their production as accurately as is not widely used in speech production studies, the
the control participants with normal hearing (see Horga present study evaluated the DOVC measure along with
& Liker, 2006). Considered together, both studies showed conventional voicing measures to examine the extent to
that a subgroup of children with cochlear implants did which several acoustic measures of voicing correspond
not demonstrate VOT values within the normal ranges. with the perceptual measures of voicing distinctions.
These results suggest a need for continued investiga- A secondary objective of the present study was to
tions of the production of voicing distinctions by children examine VOT values of stop consonants produced by
with hearing impairments. children fitted with cochlear implants in relation to nor-
One area pertaining to voicing production that needs mative data and to trained listeners’ judgments of the
further research is the identification of a good acoustic voicing errors. Specifically, we examined average VOT
measure that corresponds to trained listeners’ judgments values of plosives produced in response to the targets /t/
of voicing errors. Studies of individuals with hearing im- and /d/ by pediatric cochlear implant users. It was ex-
pairments and phonological disorders have revealed that pected that children who demonstrated VOT values out-
some of the commonly used acoustic measures, such as side the normal ranges may not necessarily be identified
mean VOT duration, may not agree well with the per- by trained listeners for producing voicing errors.
ceptual judgments of voicing production. For example, To summarize, the present study explored the util-
Catts and Jensen (1983) showed that children judged by ity of the DOVC measure in identifying voicing errors in
listeners with normal hearing to accurately distinguish children with cochlear implants. In addition, this study
between voiced and voiceless stops in their productions examined the perceptual relevance of the DOVC measure
did not necessarily demonstrate VOT values comparable and two commonly used VOT-based measures, namely,
with their age-matched peers. In another study by Horga mean VOT and DVOT. To that end, VOT measures of

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syllable–initial /t/ and /d/ were examined in the speech to the target words “tip” and “dip” in the context of a
samples of 10 children fit with a cochlear implant using carrier sentence via headphones. Only the target sounds
both phonetic transcription and acoustic analyses. /t/ and /d/ were transcribed. The transcription was car-
ried out in a two-step process. First, two graduate stu-
dents performed a broad transcription of all occurrences
of /t/ and /d/s to identify the talkers who produced the
Method target sounds inaccurately. The agreement between the
Participants transcribers was 100%. Second, the speech scientist per-
formed narrow transcription of the syllable–initial /t/
Talkers. Participants included 10 children with pre-
and /d/s produced by talkers that were identified in the
lingual deafness (S1–S10) who had cochlear implant
first step as having made production errors. All tran-
experience of at least 4 years. Information concerning
scribers were blind to the results of the acoustic data.
age, gender, age of implantation, length of implant use,
and speech intelligibility scores (assessed as described in Acoustic analyses. VOT values were measured from
Tobey, Geers, Brenner, Altuna, & Gabbert, 2003) is both waveform and spectral displays via Brown Lab Inter-
reported in Table 1. Participants were monolingual speak- active Speech System ( BLISS) speech analysis software
ers of American English and currently used the oral–aural (Mertus, 2002). VOT was measured as the duration
mode of communication. Participants were paid for their between the release of initial stop consonants and the
participation in the study. onset of the first glottal pulse. For all productions of /d/
with prevoicing, VOT was measured as the time lapse
Phonetic transcribers. Three volunteers performed
between the onset of prevoicing to the onset of the con-
phonetic transcription of the syllable–initial /t/ and /d/s.
sonantal burst.
Two of the three transcribers were students enrolled in
the communication disorders program at the University Mean VOT for /t/ and /d/ were determined for each
of Texas at Dallas. Both students were trained in pho- talker by calculating the average VOT values across
netics. The third transcriber was a speech scientist who several repetitions of /t/ and /d/. DVOT for each talker
had several years of experience in teaching graduate and was calculated by obtaining the difference between mean
undergraduate phonetics courses. VOT for /t/ and mean VOT for /d/. Finally, the DOVC
measure was calculated for each talker by obtaining the
difference between the lowest VOT value of /t/ and the
Speech Materials and Procedure highest VOT value of /d/ on the basis of 12 repetitions of
Children were familiarized with the speech mate- /t/ and /d/.
rials prior to completing the experimental task. Partici- Mean VOT, DVOT, and the DOVC measures were
pants read the target words “tip” and “dip” embedded in calculated from only those productions that represented
the following carrier sentence: “It’s a _______ again.” correct manner of articulation. That is, on the basis of
The consonants /t/ and /d/ were chosen as stimuli be- phonetic transcription data, only productions that rep-
cause recent studies of children with cochlear implants resented correct manner of articulation (“good plosives”)
have reported VOT values for these consonants (e.g., were selected for analysis. In other words, similar to that
Uchanski & Geers, 2003). Participants read each target reported in Uchanski and Geers’s (2003) study, if an
word from an index card, 12 times, in a random order, re- intended plosive was produced with an incorrect place of
sulting in a total of 240 target productions (10 talkers × articulation (e.g., /p / or /g /), then that production was in-
2 syllables × 12 repetitions). For participant S2, only cluded for analysis. However, if the intended alveolar
11 repetitions of each target word were available for anal- plosive was produced with a different manner (e.g., /s/),
ysis because of poor recording quality. then that production was eliminated from the analysis.
Phonetic transcription. Phonetic transcription was Table 2 shows the total number of tokens that were used
used as a perceptual measure. The transcribers listened for acoustic analysis, after the productions with incorrect

Table 1. Demographic information for 10 pediatric users (S1–S10) of cochlear implants.

Variable S1 S2 S3 S4 S5 S6 S7 S8 S9 S10

Gender Female Female Female Male Male Female Female Female Female Male
Age (years;months) 7;2 7;9 10;0 10;2 10;4 10;6 12;0 13;8 13;10 15;3
Implanted age (years;months) 2;1 3;9 2;0 6;0 2;7 5;0 5;11 7;7 5;0 3;0
Length of cochlear implant use (years;months) 5;1 4;0 8;0 4;2 7;7 5;6 6;1 6;1 8;10 11;5
Speech intelligibility (%) 95 92 99 36 84 94 86 47 89 84

Bharadwaj & Graves: Efficacy of the DOVC Measure 631

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Table 2. Production errors in response to targets /t/ and /d/ by for each talker were compared with normative data.
talkers S4, S5, S6, and S8. Finally, mean VOT, DOVC, and DVOT measures were
examined in relation to phonetic transcription data.
No. of tokens
chosen for
Talker Target No. of errors Substitutions acoustic analysis
Results and Discussion
S4 /t/ 1/12 [h] 11 Phonetic Transcription
/d/ 8/12 [t] 12
The broad transcription carried out by the two grad-
S5 /t/ 12/12 [d], [v], or [z] 4
uate students identified 4 talkers (S4, S5, S6, and S8) as
/d/ 10/12 [d ], [dh], [t], or [h]
w 4
having produced voicing errors. After listening to the en-
S6 /t/ 0/12 12 tire data set to confirm that the other talkers had pro-
/d/ 1/12 [t] 12 duced the alveolar stop consonants correctly, the speech
S8 /t/ 0/12 12 scientist performed narrow transcription of the target /t/
/d/ 11/12 [t] 12 and /d/ productions of S4, S5, S6, and S8. Table 2 shows
the number and types of errors that these talkers made.
All 4 talkers made errors in /d/ production, including as-
manner were eliminated from the data set. Table 3 and piration, substitution of /d/ with a fricative, and voicing
Figure 1 (discussed later) reflect VOT data from tokens errors. Only 2 talkers—S4 and S5—demonstrated er-
produced with correct manner. There were no noteworthy rors in /t/ production. These errors included excessive
changes in the average VOT, DVOT, or the DOVC values aspiration, substitution of /t/ with a fricative, and voic-
computed from all tokens versus tokens produced with ing errors. Thus, phonetic transcription identified
only correct manner. talkers S4, S5, S6, and S8 as producing errors in voicing,
To establish interjudge reliability, 10% of the data place, and manner of articulation.
were reanalyzed by a second judge. The mean absolute It is interesting to note that talkers S4, S5, and S8,
difference in VOT for /t/ measured by the two judges was who demonstrated substantial errors (compared with
1.3 ms (a measurement error of 1.45%). Similarly, the S6, who produced only one error), also received poorer
mean absolute difference in VOT for /d/ measured by the speech intelligibility scores than the rest of the talkers
two judges was 0.3 ms (a measurement error of 0.3%). A in the study (see Table 1). This finding perhaps indicates
Pearson product–moment correlation coefficient was com- that the talkers who are able to produce voicing dis-
puted to examine the relationship between measurements tinctions are also able to produce other features of speech
from the two judges. The correlation was strong and highly correctly.
significant (r = .99, p < .01), indicating high interjudge
reliability.
Acoustic Analyses
The acoustic measures were subjected to several
analyses. An analysis of variance was conducted to deter- Mean VOT duration. Mean VOT values were an-
mine whether each talker produced a statistically signif- alyzed in two ways. First, for each talker, a one-way
icant difference in VOT values for voiced versus voiceless analysis of variance was conducted using consonant as a
target sounds. In addition, mean VOT and DVOT values factor to examine whether each talker produced a reliably
different mean VOT for /t/ versus /d/. On the basis of
phonetic transcription, only tokens that were produced
Table 3. Analysis of variance results for talkers who showed a with correct manner were included in the analysis. The
significant difference (p < .01) between mean voice onset time analysis revealed a significant main effect ( p < .01) of
values of stop consonants produced with correct manner in
consonant for all talkers except S5 and S8 (see Table 3).
response to targets /t/ and /d/.
The results show that only 2 talkers—S5 and S8—did
not reliably differentiate between voiced versus voice-
Talker F ratios
less cognates. However, it should be noted that the tran-
S1 F (1, 11) = 256.3 scribers identified 4 talkers—S4, S5, S6, and S8—as
S2 F (1, 10) = 49.1 producing voicing errors. These results suggest that the
S3 F (1, 11) = 223.2 approach of examining whether a talker produced re-
S4 F (1, 10) = 19.4 liably different VOT values for voiced versus voiceless
S6 F (1, 11) = 118.5 stop consonants may not entirely agree with trained
S7 F (1, 11) = 299.6 listeners’ judgments of voicing errors.
S9 F (1, 11) = 1321.9
S10 F (1, 11) = 275.8 Second, the mean VOT values for all talkers in the
present study were compared with available normative

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Figure 1. Voice onset time (VOT) distributions for targets /t/ and /d/ produced by participants S1–S10. The distributions represent VOT values
grouped into 20-ms bins for tokens produced with only correct manner. Values associated with the discreteness of voicing category are shown on the
lower right corner of the VOT distributions. An asterisk indicates a significant difference (p < .01) between mean VOT values for /t/ versus /d/.

data (Uchanski & Geers, 2003; Zlatin & Koenigsknecht, In all, talkers S3, S4, S7, S8, and S9 demonstrated
1976). Table 4 shows distributional characteristics for mean VOT values for /t/ and /or /d / outside normal
VOT values of /t/ and /d/ tokens produced with correct ranges. However, phonetic transcription showed voicing
manner by all participants. In addition, normative data production to be accurate in talkers S3, S7, and S9. As
for VOT values of alveolar stop consonants produced by expected, findings from mean VOT data support those of
6- and 8- to 9-year-old children are shown in Table 4. As Catts and Jensen (1983) and suggest that the talkers
shown in Table 4, mean VOT values for talkers S1, S2, S4, who are judged by transcribers as producing accurate
S6, S7, and S8 (mean listening age of 5 years, 2 months) voicing may not necessarily demonstrate VOT values
were compared with normative data provided by Zlatin similar to their age-matched controls. The findings
and Koenigsknecht (1976) for 6-year-old children. Like- suggest that listeners rely on several cues besides VOT
wise, mean VOT values for /t/ and /d/ produced by talkers duration for making judgments concerning accurate
S3, S5, S9, and S10 (mean listening age of 8 years, production of voicing distinctions.
11 months) were compared with normative data provided DVOT. Normative data for mean DVOT reported by
by Uchanski and Geers (2003) for 8- to 9-year-old chil- Zlatin and Koenigsknecht (1976) for children with nor-
dren. These comparisons revealed that the VOT values mal hearing ranged approximately from 36 to 70 ms.
for /t/ produced by talkers S3, S7, S8, and S9 differed from Similarly, Uchanski and Geers (2003) reported a DVOT
the normative data by more than one standard deviation. range of 21–83 ms for 8- to 9-year-old children with nor-
In addition, VOT values for /d/ produced by talkers S4 and mal hearing. Only 2 of the current talkers—S5 and S8—
S8 differed from the normative data by more than one produced DVOT values outside this range (16.1 ms and
standard deviation. 11.63 ms, respectively). The rest of the talkers produced

Bharadwaj & Graves: Efficacy of the DOVC Measure 633

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Table 4. Means (M), standard deviations (SD), voice onset time (VOT) range, and the discreteness of voicing category (DOVC) values for tokens
produced with correct manner in response to the targets /t/ and /d/ by participants S1–S10.

/t/ /d/

Participant M (ms) SD Range (ms) M (ms) SD Range (ms) DVOT (ms) DOVC

S1 107.6 18.55 66.06 31.5 5.15 19 76.0 35.9
S2 80.82 27.04 71.04 17.72 9.42 30 63.1 13.1
S4 86.80 26.62 88.48 50.02 33.54 100.9 36.77 –58.8
S6 82.54 15.06 50.41 26.69 9.05 39.80 55.8 –1.2
S7 115.3 21.72 82.84 16.98 3.99 14.67 98.3 73.9
S8 114.60 15.45 55.57 102.97 30.19 117.55 11.63 –36.89
ZK 68.4 23.2 120 12.1 20.1 120 56.3 –1.00
S3 109.9 23.41 85.53 7.82 1.99 5.44 102.1 55.0
S5 45.22 16.89 40.61 29.09 15.58 35.87 16.13 –27.5
S9 106.2 11.88 39.86 –36.11 7.51 26.03 142.3 102.6
S10 69.01 11.36 38.43 16.19 3.63 11.45 52.8 20.1
UG 72 15 61 17 5 24 55 15

Note. ZK = normative data from Zlatin and Koenigsknecht’s (1976) study for 6-year-old children; UG = normative data from Uchanski and Geers’s
(2003) study for 8- to 9-year-old children.

DVOT within normal ranges. Thus, whereas transcribers for the same 3 talkers (S4, S5, and S8) who had dem-
identified S4, S5, S6, and S8 as producing voicing errors, onstrated substantial overlap between their /t/ and /d/
only S5 and S8 produced delta VOT values outside the VOT distributions and who had been identified by tran-
normal range. This finding suggests that DVOT captures scribers as producing voicing errors. This finding should
some but not all talkers who produce overlapping VOT be confirmed in future studies to further evaluate the
distributions because it considers only mean VOT values potential application of the DOVC measure in clinical
and disregards outliers. settings.
VOT distributions and DOVC. To plot the frequency In summary, the DOVC measure appears to be a per-
distributions for each participant, the VOT values were ceptually relevant acoustic measure because it quantifies
grouped into 20-ms intervals. Figure 1 shows VOT dis- the separation of the voiced and voiceless distributions by
tributions for participants S1–S10. The DOVC values taking into account the end points of the distributions.
are reported in the lower right corner of the distributions It is well established that more than one type of acoustic
in Figure 1. Negative values reflect overlapping distri- cue may lead to the same phonetic percept. Thus, a lis-
butions, whereas positive values reflect nonoverlapping tener may not necessarily rely on just one cue. None-
distributions. Talkers S4, S5, S6, and S8 demonstrated theless, it is striking that the DOVC measure captured
negative values, whereas the rest demonstrated positive that same set of talkers that the transcribers identified
DOVC values, reflecting well-separated distributions. as producing voicing errors. Although these findings are
Talker S6 showed a small negative value, suggesting important, they must be considered as preliminary and
minimal overlap. In fact, phonetic transcription also in- should be extended to a wider subset of consonants pro-
dicated only one instance of voicing error for this talker. duced by a larger sample of talkers. In addition, it would
The DOVC measure therefore identified the 4 talkers be valuable to supplement the phonetic transcription
selected by the transcribers as producing voicing errors, data with an additional perception measure, such as a
suggesting that this measure corresponds well with the VOT identification experiment, to evaluate further the
judgments provided by trained listeners. clinical/perceptual relevance of the DOVC measure.
One practical concern that could be raised with
reference to the DOVC measure is whether it can be used
in a clinical setting and whether the DOVC measure
Summary and Conclusions
based on a smaller sample of voiced and voiceless con- The efficacy of the DOVC measure in identifying
sonants would also yield perceptually relevant informa- voicing errors was evaluated by examining consonants
tion. To address this issue, the DOVC measure was /t/ and /d/ produced by 10 pediatric cochlear implant
recalculated for each talker using only the first five users. Phonetic transcription of syllable–initial /t/ and
tokens of the words “tip” and “dip” (instead of the /d/ was also carried out to assess how well various VOT-
12 tokens each). The results show negative DOVC values based acoustic measures (mean VOT, DVOT, and the

634 Journal of Speech, Language, and Hearing Research • Vol. 51 • 629–635 • June 2008

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DOVC) correspond to trained listeners’ judgments of voic- Horga, D., & Liker, M. (2006). Voice and pronunciation of
ing production accuracy. Phonetic transcription by three cochlear implant speakers. Clinical Linguistics & Phonetics,
20, 211–217.
individuals with phonetic training revealed voicing er-
rors in 4 of the 10 talkers. Of the acoustic measures Jiang, J., Chen, M., & Alwan, A. (2006). On the perception of
voicing in syllable–initial plosives in noise. The Journal of
assessed here, only the DOVC measure captured these the Acoustical Society of America, 119, 1092–1105.
same 4 talkers. Mean VOT and DVOT measures iden-
Lane, H., Wozniak, J., Matthies, M., Svirsky, M., &
tified a different subset of talkers who demonstrated Perkell, J. (1995). Phonemic resetting versus postural
VOT values outside normal ranges. Thus, the DOVC adjustments in the speech of cochlear implant users: An
measure corresponded with the perceptual judgments exploration of voice-onset time. The Journal of the Acous-
by trained listeners better than any other acoustic mea- tical Society of America, 98, 3096–3106.
sures examined in the present study. Although the sam- Lisker, L., & Abramson, A. S. (1964). A cross language study
ple size is limited, the present data indicate that the of voicing in initial stops: Acoustical measurements. Word,
DOVC measure may yield perceptually relevant infor- 20, 384–422.
mation concerning voicing errors. In addition, prelimi- Mertus, J. (2002). Brown Lab Interactive Speech System
nary data suggest that the DOVC measure can be used ( BLISS) [Computer software]. Providence, RI: Brown
University.
to objectively evaluate VOT-related outcomes in clinical
settings. Additional studies are necessary to extend the Monsen, R. B. (1976). The production of English stop consonants
in the speech of deaf children. Journal of Phonetics, 4, 29–41.
findings of the present study to a wider set of consonants
produced by a large number of normally developing chil- Ryalls, J., & Larouche, A. (1992). Acoustic integrity of
speech production in children with moderate and severe
dren and individuals with speech disorders. hearing impairment. Journal of Speech and Hearing
Research, 35, 88–95.

Acknowledgments Tobey, E. A., Geers, A. E., Brenner, C., Altuna, D., &
Gabbert, G. (2003). Factors associated with development of
This work was supported by National Institute on Deaf- speech production skills in children implanted before age
ness and Other Communication Disorders Grant R03DC007052 five. Ear and Hearing, 24, 36S–45S.
awarded to the first author. The authors would like to thank Uchanski, R. M., & Geers, A. E. (2003). Acoustic character-
participants and their families for their contributions. Thanks istics of the speech of young cochlear implant users: A com-
to Deborah Rekart and Anupama Jayaraman for their help in parison with normal-hearing age-mates. Ear and Hearing,
phonetic transcription work. Thanks also to William F. Katz 24, 90S–105S.
and Raksha Anand for their helpful comments on an earlier Waldstein, R. S. (1990). Effects of postlingual deafness on
version of this article. speech production: Implications for the role of auditory
feedback. The Journal of the Acoustical Society of America,
88, 2099–2114.
References Wambaugh, J. L., West, J. E., & Doyle, P. J. (1997). A VOT
analysis of apraxic/aphasic voicing errors. Aphasiology, 11,
Catts, H. W., & Jensen, P. J. (1983). Speech timing of 521–532.
phonologically disordered children: Voicing contrast of
initial and final stop consonants. Journal of Speech and Zlatin, M. A., & Koenigsknecht, R. A. (1976). Development
Hearing Research, 26, 501–510. of the voicing contrast: A comparison of voice onset time
in stop perception and production. Journal of Speech and
Economou, A., Tartter, V. C., Chute, P. M., & Hellman, S. A. Hearing Research, 19, 93–111.
(1992). Speech changes following reimplantation from a
single-channel to a multichannel cochlear implant. The
Journal of the Acoustical Society of America, 92, 1310–1323. Received April 12, 2006
Forrest, K., & Rockman, B. K. (1988). Acoustic and percep- Revision received December 14, 2006
tual analysis of word-initial stop consonants in phonologi-
Accepted September 17, 2007
cally disordered children. Journal of Speech and Hearing
Research, 31, 449–459. DOI: 10.1044/1092-4388(2008/045)
Higgins, M. B., McCleary, E. A., Carney, A. E., & Schulte, Contact author: Sneha V. Bharadwaj, Callier Center,
L. (2003). Longitudinal changes in children’s speech and University of Texas at Dallas, 811 Synergy Park Boulevard,
voice physiology after cochlear implantation. Ear and Richardson, TX 75080. E-mail: snehab@utdallas.edu.
Hearing, 24, 48–70.

Bharadwaj & Graves: Efficacy of the DOVC Measure 635

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Efficacy of the Discreteness of Voicing Category (DOVC) Measure for
Characterizing Voicing Errors in Children With Cochlear Implants: A Report

Sneha V. Bharadwaj, and Amanda G. Graves
J Speech Lang Hear Res 2008;51;629-635
DOI: 10.1044/1092-4388(2008/045)

This information is current as of August 13, 2010

This article, along with updated information and services, is
located on the World Wide Web at:
http://jslhr.asha.org/cgi/content/full/51/3/629

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