Ming-Chung Cheng Voice Onset Time of Syllable-Initial Stops in Sixian Hakka ◆ 193 ◆ Voice Onset Time of Syllable-Initial Stops in Sixian Hakka: Isolated Syllables Ming-Chung Cheng Institute of Hakka Language and Communication National United University Associate Professor Abstract This study investigates the “voice onset time” (VOT) variation in syllable-initial stops of Sixian Hakka in isolated syllables, according to factors including place of articulation (PoA), following vowel context, and the speakers’ age and gender. Thirty-six participants provided speech recordings. They were required to repeat a randomized list of 36 speech stimuli constructed by using 6 syllable- initial stops [p, t, k, p h , t h , k h ] preceding 3 corner vowels [i, u, a] in 2 high-level tones [55, 55]. A total of 3,888 samples were measured for VOT values in PRAAT. The research results showed that the factors other than gender affected the VOT production of Hakka syllable-initial stops. In accordance with observations in previous sociolinguistic studies of gender, gender differences concerning the VOT absolute values were also observed despite showing no statistically significant differences. Furthermore, the factorial interaction between the stops’ PoA and the following vowel context, which was discussed in detail, showed that vowel height has a stronger effect on VOT than vowel frontness. To conclude, this study substantially contributes to the understanding of VOT and its variation in Hakka, and to further comparisons of the VOT systems of stops between Hakka and other Chinese dialects or foreign languages, particularly for foreign spouses who immigrated to Hakka villages. Keywords: age, gender, Hakka, stop, voice onset time Corresponding author: Ming-Chung Cheng, E-mail: [email protected]Manuscript received: Feb. 25, 2013; Modified: Apr. 11, 2013; Accepted: Apr. 12, 2013 doi: 10.6210/JNTNULL.2013.58(2).08
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Ming-Chung Cheng Voice Onset Time of Syllable-Initial Stops in Sixian Hakka ◆ 193 ◆
Voice Onset Time of Syllable-Initial Stops in Sixian Hakka: Isolated Syllables
Ming-Chung ChengInstitute of Hakka Language and Communication
National United University Associate Professor
Abstract
This study investigates the “voice onset time” (VOT) variation in syllable-initial stops of Sixian
Hakka in isolated syllables, according to factors including place of articulation (PoA), following
vowel context, and the speakers’ age and gender. Thirty-six participants provided speech recordings.
They were required to repeat a randomized list of 36 speech stimuli constructed by using 6 syllable-
initial stops [p, t, k, ph, th, kh] preceding 3 corner vowels [i, u, a] in 2 high-level tones [55, 55]. A total
of 3,888 samples were measured for VOT values in PRAAT. The research results showed that the
factors other than gender affected the VOT production of Hakka syllable-initial stops. In accordance
with observations in previous sociolinguistic studies of gender, gender differences concerning the
VOT absolute values were also observed despite showing no statistically significant differences.
Furthermore, the factorial interaction between the stops’ PoA and the following vowel context, which
was discussed in detail, showed that vowel height has a stronger effect on VOT than vowel frontness.
To conclude, this study substantially contributes to the understanding of VOT and its variation in
Hakka, and to further comparisons of the VOT systems of stops between Hakka and other Chinese
dialects or foreign languages, particularly for foreign spouses who immigrated to Hakka villages.
Keywords: age, gender, Hakka, stop, voice onset time
◆ 194 ◆ Voice Onset Time of Syllable-Initial Stops in Sixian Hakka Ming-Chung Cheng
1. Introduction
Stops (or plosives) are a significant group of consonants that exists in all world languages
(Henton, Ladefoged, and Maddieson 1992; Maddieson and Ladefoged, 1996).1 Articulatorily,
producing stops requires that the airstream in the vocal tract be totally blocked and the closure be
briefly held. Once the blockage is released, the airstream behind the oral constriction suddenly
escapes from the mouth. The temporal interval between the release of the constriction and the onset
of vocal cord vibration is known as voice onset time (VOT) (Klatt 1975; Lisker and Abramson 1964;
Zlatin 1974).2 VOT has long been viewed as a reliable temporal-acoustic measure for the distinction
of voicing and aspiration in stops, and can be generally classified into three categories, voice lead,
short lag and long lag, depending on whether voicing proceeds or follows the release burst (voiced
vs. voiceless) and how long the airflow release lasts (aspirated vs. unaspirated). In principle, stops
are able to be uttered in any places in the vocal tract, but they tend to cross-linguistically occur in
three common places: bilabial, alveolar, and velar (Gamkerlidze 1978; Maddieson 1984).
The current study has three purposes. First of all, this study aims to investigate VOT and
its variation of syllable-initial stops in Hakka. Due to the universal existence of stops, and the
convenient assess and great progress of modern technology in acoustic analysis, a great body of
literature has been conducted to investigate the VOT issues in recent decades, such as (1) cross-
linguistic surveys (e.g., Cho and Ladefoged 1999; Keating, Linker, and Huffman 1983; Shimizu
1996; Wu 2009), (2) language-specific research (e.g., Cho, Jun, and Ladefoged 2002; Docherty
1992; Gósy 2001; Han and Weitzman 1970; Helgason and Ringen 2008; Kong, Beckman, and
Edwards 2011; Nielsen, 2011; Öğüt et al. 2006; Riney et al. 2007; Ringen and Suomi 2012; Rosner
et al. 2000; Williams 1977), (3) second and foreign language teaching and learning (e.g., Antoniou
et al. 2011; Chao and Chen 2008; Chao, Khattab, and Chen 2006; Chung 2010; Flege and Eefting
1987; Hazan and Boulakia 1993; Kang and Guion 2006; Kehoe, Lleó, and Rakow 2004; Khattab
1 For possible reasons for the cross-language existence of stops, see Ran’s (2008, 67-70) explanations. 2 Besides VOT, other acoustic characteristics for distinguishing stops in different places of articulation (PoAs)
are spectral peaks of the release bursts, formant transitions and silent periods. Stops in different PoAs will have their spectral energies centralized in different frequency ranges: bilabials (500~1500 Hz), alveolars (over 4000 Hz) and velars (1500~4000 Hz) (T. Lin and Wang 2005; Tsao 1996; Wu and Lin 1989). Likewise, stops of different PoAs have an influence on the formant transitions of the following vowels (Wu and Lin 1989). As for silent gaps, they are the indispensible ingredient for stops and crucial element for perceiving stops (Liang 2001; Ren 1981). In general, the lengths of stops’ silent periods correspond inversely to their PoAs. To be specific, the more posterior the stop’s PoA is, the shorter the silent period will be. For detailed discussion, refer to Ran (2008).
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2000; Liao 2005; Ogasawara 2011; Riney and Takagi 1999; Simon 2010; Thornburgh and Ryalls
1998; Yavaş and Wildermuth 2006), and (4) clinical and pathological practice (e.g., Auzou et al.
2000; Baker et al. 2007; Fischer and Goberman 2010; Jäncke 1994; Khouw and Ciocca 2007; Liu et
al. 2007, 2008; Ng and Wong 2009; Ringen and Suomi 2012; Tseng 1994; Tsui and Ciocca 2000).
Despite the wide research, most of the literature concentrated on western languages (e.g., English
and French). Comparatively, little attention is guided to Chinese dialects / varieties.3 For this reason,
this study is specific to Hakka, with an aim to complementing the paucity of Hakka VOT studies.
The second purpose of this study is to decide the exact VOT categories to which Hakka stops
belong. There are six voiceless stops in Hakka, appearing in three places (bilabial [p, ph], alveolar
[t, th], and velar [k, kh]), and in two manners (unaspirated vs. aspirated). These stops are cross-
linguistically common, but a systematic, large-scale investigation of the VOT variation is still in
urgent demand for the following reasons. First, it is broadly reported that VOT varies under many
affecting factors (see section 2 for a review). Yet, how these factors influence the VOT production
in Hakka stops is scarcely examined, let along their extent and interaction.4 Second, VOT varies
across languages, falling into types along the VOT continuum on a language-particular basis. Cho
and Ladefoged (1999), for example, separate voiceless unaspirated and aspirated stops into four
3 Mandarin Chinese seems to be an exception. A considerable amount of research (Liao 2005; Peng 2009; Ran 2008; Rochet and Fei 1991; Wu 2004; Wu and Lin 1989; among others) has explored the VOT issue in Mandarin Chinese, irrespective of the small number of participants in most of these studies. In addition, on account of the worldwise popularity of learning Mandarin Chinese as a foreign or second language, there are more and more studies examining production problems of stops by comparing VOT between Mandarin Chinese and these foreigners’ native languages, like English (Chao and Chen 2008; Shi and Liao 1986; Wang, Chen, and Tsai 2006), German (Wen, Ran, and Shi 2009), Japanese (Wang and Shangguan 2004), Korean (Gao 2001), Indonesian (Y.-G. Lin and Wang 2005), and so forth.
4 To my knowledge, few studies investigated the VOT production of Hakka stops, except Liang (2005) and Peng (2009). On the basis of southern Sixian Hakka, Liang (2005) probed the VOT production of syllable-initial stops by 20 participants (10 males and 10 females) with their ages ranging from 27 to 72. Not aiming specifically at stops’ VOT, he simply provided a general VOT exploration of Hakka stops of different places of articulation, without taking other affecting factors into consideration. Peng (2009) collected 11 males’ and 10 females’ production of six syllable-initial stops in Sixian Hakka followed by [i, a, u], and examined the VOT variation under factors, such as place of articulation, vowel context, tone and gender. In comparison with Liang (2005), she supplied more detailed explanations of the VOT variation in Hakka stops, but there are some weaknesses awaiting improvements. First of all, similar to Liang, the age ranges of her participants were extremely wide (36~80 years old), so she was unable to take the age factor into consideration. Second, there were only 21 subjects (10 males and 11 females) taking part in her study. Third, she claimed that the participants were all native speakers of Sixian Hakka, but their residences were not clearly stated. It is well-known that Hakka is always in linguistic contact with, and is influenced by, Southern Min and Mandarin Chinese in Taiwan. This may give rise to a negative effect on VOT. For this reason, this study will recruit participants inhabiting in Miaoli County, the most intensely populated area by speakers of (northern) Sixian Hakka. Hakka is also the daily language used by these people recruited in this study, so the homogeneity of the participants can be ensured, and the reliability of the study can be guaranteed.
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90 ms), and highly aspirated (over 90 ms). On the basis of Cho and Ladefoged’s elaborate typology,
which VOT categories do the roughly-divided Hakka stops belong to? Obviously, both issues wait
for further probations.
The third purpose of this study is to set up a VOT reference norm for foreigners’ learning
Hakka or instructors’ teaching Hakka. In recent decades, plenty of foreigners, called foreign spouses,
usually females, have married to Hakkas, and immigrated into Hakka villages. On account of their
diverse language backgrounds (e.g., Vietnamese, Indonesia, Thai, Filipino (Tagalog), etc.), there are
differences in the systems of stop consonants. For instance, though there exist [p, t, k] in Vietnamese,
[p] can not occur syllable-initially. Moreover, there are no aspirated stops in Tagalog. In addition
to [p, t, k, ph, th, kh], there are voiced stops [b, d] in Thai which are lacking in Hakka. All these
differences in the stop systems across languages make it a must to well survey Hakka stops’s VOT
in order to mutually compare the stop systems of foreign languages with Hakka, give the Hakka
instructors a reference standard and help these foreign spouses learn Hakka well. Actually, the issue
of stop learning problems between Mandarin and foreign languages has been extensively compared
(see footnote 3 for some literature), but similar explorations are still lacking between Hakka and
foreign languages, except English. The study hopes to set up a VOT reference norm. With this norm,
in addition to Hakka language learning / teaching, Hakka-language studies can be further extended
to interrelated topics, like speech recognition and synthesis, pathological treatment, and Hakka as a
second / foreign language for foreigners, all of which have been always missing from Hakka studies,
and call for further examinations.
In view of the purposes stated above, conducting a VOT study of Hakka stops is quite
necessary, and motivates this study. This study is organized as follows. Section 2 offers a concise
review of the factors that affect VOT. Section 3 presents the methods in this study, inclusive of
participants, recording stimuli, speech recording procedure, and acoustic and statistical analysis.
Section 4 shows the results of the effects on VOT resulting from the factors in investigation. Section
5 discusses the experimental results generally, along with special attention given to the interaction
between stops’ place of articulation and following vowel context. Section 6 concludes this study,
together with some suggestions for future research.
2. Affecting Factors for VOT
As a temporal-acoustic measure, VOT is contextually sensitive, and is influenced by numerous
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factors. For example, studies in VOT have indicated that speaking rate is decisive to the production
of VOT in voiceless long-lag plosives (Beckman et al. 2011; Kessinger and Blumstein 1997, 1998;
Magloire and Green 1999; Pind 1995, 1996; Volaitis and Miller 1992), with faster speaking rate
leading to shorter VOT values. Nonetheless, the effect of speaking rate upon VOT is not obvious in
voiceless short-lag and voiced plosives. Besides, utterance type is reported to affect VOT (Baran,
Laufer, and Daniloff 1977; Lisker and Abramson 1967), with VOT longer in isolated words than
in phrases and sentences. Speech register affects VOT as well, with infant-directed speech having
longer VOT than adult-directed speech (Englund 2005; Sundberg and Lacerda 1999). VOT varies
across fundamental frequency (F0) as well, with longer VOT for voiceless stops spoken at relatively
high F0, compared to VOT spoken at low or medium F0 (McCrea and Morris 2005). Subsequently,
this study will review several affecting factors of VOT decisive to the following discussion (i.e.,
place of articulation, following vowel context, and speakers’ age and gender).5
Place of articulation is by far the most-studied factor for VOT variation. With all else equal,
there is a general pattern existing between stops’ articulatory positions and VOT lengths. Specifically,
the more posterior the point of occlusion is, the longer the VOT will be. Being attributed to universal
phonetic implementation rules conditioned by physiological constraints (Fischer-Jørgensen 1980),
this pattern has been broadly supported from cross-linguistic or language-specific explorations (e.g.,
Abdelli-Beruh 2009; Helgason and Ringen 2008; Jessen and Ringen 2002; Peterson and Lehiste
1960; Riney et al. 2007). For example, Lisker and Abramson (1964) and Cho and Ladefoged (1999)
investigated the stops in 11 and 18 languages respectively, indicating that the commonest sequence
is velars > alveolars > bilabials. Further, Cho and Ladefoged summarized six physiological and
aerodynamic characteristics of speech production to explicate VOT variation resulting from different
articulatory positions of stops.6 Still, not all languages conform to this pattern. For example, in Table
1, bilabial stops have longer VOT than alveolar stops in aspiration (Cantonese, Eastern Armenian and
5 Readers may have a question in mind. Given so many affecting factors, why did the author just choose these four? This was because the restriction of time and financial support of the research precluded the author from taking too many factors into concern. Thus, the author chose the factors that were the most commonly studied across languages, putting aside others for further research. As a matter of fact, even in these factors, little is known of stops’ VOT of Hakka. Hence, to understand the VOT variation under these affecting factors will contribute not only to the VOT realization in Hakka, but to the assistance of foreigners’ learning Hakka. This is the reason why the author selected these factors in this research.
6 The six physiological / aerodynamic characteristics consist of (1) the volume of the cavity behind the point of constriction, (2) the volume of the cavity in front of the point of constriction, (3) movement of articulators, (4) extent of articulatory contact area, (5) change of glottal opening area, and (6) temporal adjustment between closure duration and VOT. For elaborate accounts, please see Cho and Ladefoged (1999, 209-213). For relevant discussion of the VOT production, also see Hardcastle (1973), Maddieson (1997) and Stevens (1998).
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Mandarin Chinese) or non-aspiration (Tamil, Navajo, Hungarian and Japanese). Dahalo seems to be
the most uncommon language in which alveolar stops come out with the longest VOT. The existence
of the deviant patterns from the general one suggests language specificity in VOT (Gósy 2001).7
Table 1 Summary of the VOT Values Reported in Some Studies
Gósy (2001) Hungarian 24.6 23.3 50.2 * * *Riney et al. (2007) Japanese 30 28.5 56.7 * * *Chao and Chen (2008) Mandarin Chinese 14 16 27 82 81 92
Note: All values are in ms.
VOT is also known to vary in different vowel contexts (Docherty 1992; Esposito 2002; Gósy
2001; Higgins, Netsell, and Schulte 1998; Klatt 1975; Port and Rotunno 1979; Rochet and Fei
1991; Smith 1978; Weismer 1979). In terms of vowel height, it has been generally agreed that stops
before high vowels have longer VOT than those before low ones (Klatt 1975; Thornburgh and Ryalls
1998; Yavaş 2002). For example, analyzing 40 males’ and 40 females’ production of English CV
syllables constructed by [p, t, k, b, d, g] in combination with [i, a, u], Morris, McCrea, and Herring
(2008) illustrated that VOT is significantly shorter before [a] than before [i, u].8 This varying
phenomenon results from the different opening degrees of the oral cavity (stricture) in the production
of different vowels and the changes in laryngeal cartilage positioning and vocal fold and vocal tract
tension (Higgins et al. 1998). Moreover, even though the number of studies is not as many as those
associated to vowel height, vowel frontness is reported to affect VOT, too.9 For instance, Gósy (2001)
explored five females’ production of Hungarian voiceless stops [p, t, k] before fourteen vowels in
CV syllables, discovering that [t, k] has longer VOT when preceding front vowels than back vowels,
7 For more thorough discussion on the relation between VOT and stops’ places of articulation, refer to Abdelli-Beruh (2009).
8 A minority of studies did not follow this generally-accepted VOT / vowel pattern. For example, in his investigation of Swedish stops, Fant (1973) reported that aspirated stops have longer VOT in front of [a] than before [i, u].
9 Contradictorily, some studies, like Chao et al. (2006) and Chen, Chao, and Peng (2007), indicated that vowel frontness did not play a role in VOT variation.
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Ming-Chung Cheng Voice Onset Time of Syllable-Initial Stops in Sixian Hakka ◆ 199 ◆
but [p] reverses the order. Investigating stops in Taiwan Mandarin and Hakka, Peng (2009) observed
that [p] in Taiwan Mandarin and [p, ph] in Hakka have longer VOT before [u] than before [i]. Similar
findings were also observed from Rochet and Fei (1991). For all such observations, neither of the
studies stated above provided full accounts of the reasons for the differences between [p, ph] and
[t, th, k, kh] before front and back vowels. This intricate issue will be explicated in great details in
section 5, in terms of the interaction among VOT, stops’ PoA and vowel context.
In addition, nonlinguistic factors, such as age and gender, are also manipulated to test whether
they affect stops’ VOT. As far as the age factor is concerned, the findings are inconsistent. Some
studies (Neiman, Klich, and Shuey 1983; Petrosino et al. 1993) manifested no significant difference
in different age groups, but old adults produce larger VOT variability and longer syllable duration
than young adults. Others (Morris and Brown 1987; Sweeting and Baken 1982) found that the age
influence emerged merely in voiceless stops, with the elderly producing shortened VOT in specific
stop consonants ([p, t] in Morris and Brown 1987; [p] in Sweeting and Baken 1982). Still others (Liss,
Weismer, and Rosenbek 1990; Ryalls, Simon, and Thomason 2004; Smith, Wasowics, and Preston
1987; Torre and Barlow 2009; Yao 2007) reported that age is a considerable factor of VOT, with a
general tendency that VOT articulated by the young is longer than that produced by the old.10
In terms of the gender factor, massive literature has shed light on this factor, and the common
pattern is that females exhibit longer VOT than males. This pattern has been supported by a variety
of studies of voiceless stops in English (Robb, Gilbert, and Lerman 2005; Ryalls and Zipprer 1997;
Swartz 1992; Sweeting and Baken 1982; Whiteside, Henry, and Dobbin 2004; Whiteside and Irving
1997, 1998; Whiteside and Marshall 2001).11 Smith (1978) and Swartz (1992) reported that females
produced longer VOT than males in English voiced stops, too. There are also a small number of
studies demonstrating no male / female difference in VOT (Morris et al. 2008; Öğüt et al. 2006;
Ryalls et al. 2004; Syrdal 1996), or even longer VOT in males than in females (Oh 2011). Clearly,
previous research in consideration of the effect of speakers’ age and gender on VOT variation has
not yet arrived at a consensus.
In a nutshell, regardless of a large size of literature relevant to the factors of VOT, little is
managed specifically to the VOT variation in Hakka. How the aforementioned factors perform to
10 In comparison with adults, children also produce more variable VOT (Koenig 2000; Smith 1978). 11 It should be noticed that, even in the same studies, the results may be inconsistent, owing to different
segments, tasks or designs (Morris et al. 2008; Smith 1978; Swartz 1992; Whiteside and Irving 1998). For instance, women were reported to produce longer VOT in [p, t, k], but men appeared to produce longer VOT in [b, d, g] (Smith 1978; Whiteside and Irving 1998).
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affect Hakka stops’ VOT is scarcely explored, and, undoubtedly, is worth further investigation. The
current study intends to achieve this goal and enhance the comprehension of the VOT issue in Hakka
stops. Additionally, VOT variation is a complicated issue. To make it simple and clear, this study
focuses simply on stops in syllable-initial positions. Only when how VOT varies in this position
becomes clear can VOT variation of stops in other linguistic positions or contexts acquire a basis for
further comparisons, either intra-linguistically or inter-linguistically.
3. Methodology
3.1 Participants
Thirty-Six Hakka people (18 males and 18 females) in Miaoli County, with Sixian Hakka as
their mother tongue, joined this study. They were divided into six gender-balanced groups with clear
separation in age (elderly: over 55, middle-aged: 35-55 and younger: 15-35). The mean ages were
25.33/42.67/59.67 years for males and 24.67/41.83/68.83 years for females. The participants were
randomly selected for speech recordings, but they were still required to match the following criteria.
At first, they speak (northern) Sixian Hakka at home and in daily conversation with other Hakka
people.12 Second, they have been living in Gongguan Township and Miaoli City at least for over
fifteen years. Third, they are free from speech, language, hearing or pathological disorders.
3.2 Speech Stimuli
This study targets at exploring the VOT variation of Hakka syllable-initial stops. A list of
36 syllables was used as speech stimuli, as listed in Table 2. These syllables were constructed by
six syllable-initial stops [p, t, k, ph, th, kh] in combination with three corner vowels [i, u, a] and two
high-level tones [55, 55].13 Excluding [tha55] and [ki55] which are lexical gaps (permissible syllables
in Hakka, but currently without lexical meanings), all remaining 34 syllables are real words and
frequently used in their daily lives.
12 Most of the participants, especially the young and the middle-aged groups, can also speak Mandarin, because Mandarin is the standard language used in education and mass media communication. In truth, Hakka people are usually bilingual in Hakka and Mandarin. This is an unavoidable fact that Mandarin has a higher social status. Moreover, some of them can even speak Southern Min, but very influently.
13 Hakka is a tone language, so every syllable bears a citation tone. On the basis of Lo (2007), there are six citation tones in northern Sixian Hakka: Yinping [24], Yangping [11], Shangsheng [31], Qusheng [55], Yinru [32] and Yangru [55], where the numbers in square brackets represent pitch values in terms of Chao’s (1930) five-point scale.
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The speech stimuli in Table 2 can be classified into two types, checked-tone and unchecked-tone
syllables, depending on whether there are [p, t, k] codas. Appearing with unreleased [p, t, k] codas,
checked-tone syllables are always produced more rapidly, and have shorter syllable duration than
unckecked-tone ones. This length difference also gives rise to different VOT variation, with VOT in
unchecked-tone syllables longer than that in checked-tone syllables (Peng 2009).14 Besides, there are
six citation tones in Sixian Hakka: four unchecked and two checked tones. If the VOT tokens under
all citation tones are collected and averaged, the resulting VOT mean values must be longer than it
will actually be. This is because tokens of unchecked tones are more than those of checked tones. To
remove the bias on the VOT means, this study took in consideration both types of syllables having
the same pitch [55], but differing simply in checked or unchecked types. Hence, this study will not
take the tone factor into discussion.
3.3 Recording Procedure
Speech recording was performed in a sound-proof room in order that high voice qualities could
be guaranteed. A unidirectional microphone (PHILIPS SBC-ME470), with sensitive frequencies
ranging from 50 Hz to 18,000 Hz, was linked to a notebook computer (ACER TravelMate 6252,
with a 2.13G Hz CPU and a 1G SDRAM), and were placed ten centimeters away from the subjects’
mouths at the chest level. Speech samples were recorded directly and digitalized into the computer
by means of PRAAT (Boersma and Weenink 2009), together with a default sampling frequency of
44.1K Hz. The samples were segmented and transformed into Wav files for further analysis.
14 The VOT lengths between unchecked tones and checked tones were compared in Peng (2009), with the result showing that VOT in the former was longer than that in the latter. However, whether there were significant VOT differences among the four unchecked tones in Hakka was not mentioned at all.
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For subjects to be familiar with the stimuli, the word list had been given to them a week before
sound recording was conducted. In the recording session, subjects were instructed to pronounce
every stimulus with the same pace and intensity. The stimuli were presented randomly. Each stimulus
was pronounced five successive times.15 The middle three were extracted for VOT measurements,
for they are comparatively stable than the first and last ones. Every subject pronounced 108 speech
tokens (36 stimuli multiplied by 3 times), and the total number of tokens for acoustic analysis was
3,888 (108×36).
3.4 Acoustic and Statistical Analysis
The collected speech tokens were measured for VOT values in all cases by visual inspection
and auditory perception, and with the help of oscillograms and (wideband) spectrograms. The
beginning of VOT was defined by the burst of release. The start of waveform periodicity was used
to determine the ending of VOT. In addition, relevant acoustic cues, such as the onset of F1 and F2
of the following vowels, were also used as additional references to demarcate the VOT duration.16
With [phi55] articulated by a middle-aged female as an illustrative example, the VOT measurement in
PRAAT was schematically shown in Figure 1. The portion in red was regarded as the VOT length of
[ph], with the release burst as the onset of VOT (marked by energy release in the waveform) and the
waveform periodicity as the offset of VOT (marked by the first pulse).
Moreover, to assess intra-rater and inter-rater reliability, one-tenth speech tokens were
randomly chosen and re-measured by the author and a research assistant having years’ experience
in conducting acoustic research. Pearson’s correlation coeff icients showed that both measurements
were positively correlated (r = .98 and r = .96 respectively, p < .001). SPSS PASW 18.0 was utilized
for statistical analysis, with a significance level set as p < .05 for all the tests.
4. Results
This section presents the statistical results of the influences upon VOT caused by the four
15 Another method of data collection and recording is to place these speech stimuli in a carrier sentence. However, the method adopted in this current study is also broadly adopted in related VOT studies (e.g., Shi 2008).
16 Different positioning references were adopted to demarcate the ending of VOT, such as the onset of formant 1 (Chao and Chen 2008), of formant 2 (Cho and Keating 2001), or of waveform periodicity (Port and Rotunno 1979; Whalen, Levitt, and Goldstein 2007). Comparing the VOT measurements on the basis of these positioning references, Francis, Ciocca, and Yu (2003) have claimed that it is the most reliable to measure VOT with reference to acoustic waveforms.
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factors under discussion (i.e., place of articulation (PoA), vowel context, gender and age). Prior
to in-depth accounts, statistical analyses were conducted in advance. A four-way mixed factorial
ANOVA showed no significant VOT differences in nonaspiration (F (8, 594) = .831, p = .576 > .05)
or in aspiration (F (8, 594) = .591, p = .786 > .05). There were still no significant differences in terms
of three-way mixed factorial ANOVAs (p > .05 for all cases). Given this statistical background, the
following discussion will proceed in the sequence: 4.1 PoA; 4.2 following vowel context; 4.3 age; 4.4
gender. Special attention will be directed to the two-way interactive influences of PoA in relation to
other factors.
4.1 Effect of PoA
The mean of VOT for every Hakka stop, averaging over following vowel context, speakers’ age
and gender, are tabulated in Table 3, together with standard deviations (SD), minimums (Min) and
maximums (Max). As previously stated, VOT tends to correlate with stops’ PoA. The more posterior
a stop’s PoA is, the longer the intrinsic VOT will be. This tendency is confirmed in this study. The
table in Table 3 shows velar stops were longer than alveolar stops in VOT; alveolar stops, in turn,
had longer VOT than bilabial stops. When the place of oral constriction moves from the anterior
Figure 1 An Illustrative Example of the VOT Measurement of [ph] in [phi55] Produced by A Middle-
Aged Female
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to the posterior within the oral cavity, the variability of VOT also increases gradually. This can be
supported by the larger and larger SD values from bilabials to velars.17 Furthermore, in accord with
Cho and Ladefoged’s (1999) classification, Hakka stops belong to the unaspirated and slightly
aspirated categories.
Separate one-way analyses of variance (ANOVAs) exhibited that the PoA effect on stops’ VOT
was significant in either non-aspiration (F (2, 645) = 361.834, p = .000 < .05) or aspiration (F (2,
645) = 106.101, p = .000 < .05). Post hoc least significant difference (LSD) multiple comparisons
indicated that significant differences appeared in [k-t], [k-p], [kh-th], [kh-ph] (p = .000 < .05 for all
cases) and [th-ph] (p = .041 < .05). No significant VOT difference was observed in [t-p] (p = .362 >
.05), in spite of their difference in the absolute VOT value. The lack of VOT length difference in [t-p]
may result from the approximacy of their articulatory positions (i.e., bilabial vs. alveolar). Given this
situation, there must be some other features to distinguish [p] from [t] (e.g., silent period, formant
transition, spectral peak frequency, etc.).
17 The VOT values of Hakka stops in Peng (2009) were 12.64 ms for [p], 15.06 ms for [t], 27.2 ms for [k], 74.22 ms for [ph], 74.28 ms for [th], and 89.94 ms for [kh]. Comparatively, the VOT values obtained in this study were shorter. This difference comes from the number of tones that were taken into concern. Peng collected speech samples of six tones in Hakka, four unchecked tones and two checked tones. Remarkably, VOT in unchecked-tone syllables is longer than that in checked-tone ones. As a result, more unchecked-tone speech samples will definitely lead to longer VOT. If syllables of Qu [55] and Yangru [55] in this study are discussed individually, the VOT values are expressed as follows. For Qu, the VOT values were 11.6 ms for [p], 13.1 ms for [t], 23.8 ms for [k], 58.6 ms for [ph], 59.5 ms for [th], and 79 ms for [kh]. For Yangru, the VOT values were 10.6 ms for [p], 11 ms for [t], 19.7 ms for [k], 46.9 ms for [ph], 50.5 ms for [th], and 65.9 ms for [kh]. The length difference between Qu and Yangru for all stops arrives at statistical significance (p = .000 < .05 for stops other than [p]; p = .013 < .05 for [p]).
Table 3 Means, SDs, and Mins/Maxs of VOT for Individual Hakka Stops
However, the VOT difference in [t-p] did not arrive at statistical significance, which may result partly
from the shortness of VOT and partly from the closeness of articulatory positions for both stops. In
fact, the same cause may also give rise to no significant VOT difference in the [pu-tu] pair.
As for the factor of following vowel context, VOT shows variances according to following
vowels. This study confirms that stops before [i, u] have longer VOT than those before [a]. High
vowels are produced with a more obstructed cavity and a less abrupt air pressure drop in the oral
cavity than low vowels. When stops in anticipation of high vowels are pronounced, the airstream
escaping from the oral cavity becomes relatively slow, so the release of the airstream (i.e., VOT)
is lengthened. What’s more, the effect of [i] and [u] on VOT is also illustrated to be different, with
[i] stronger than [u] for [t, k, ph, th, kh]. For [p], there is no significant VOT difference between
[pi] and [pu]. As previously mentioned in section 4.2, there is no significant difference in VOT in
the pair of [i-u] (p = .471 > .05). Specifically, vowel frontness seems to play no role in the VOT
production of Hakka syllable-initial stops. In fact, other than [p], the VOT difference between [i]
and [u] in stops can be argued to be crucially relative to vowel height instead of vowel frontness.
As indicated in Ladefoged (2001), vowels specified as [+high] may not have an equal tongue height
in real articulation. This viewpoint is well captured in Cheng’s (2012) acoustical exploration of the
vowel pattern of Sixian Hakka. As shown in Figure 5, front vowels [i, e] are produced with higher
tongue positions than the corresponding back vowels [u, o], no matter which gender is taken into
consideration.18
18 In Figure 5, there is a gender difference in vowel space area, with females’ larger than males’. Moreover, compared with females’ [u], males’ [u] tends to be unstable due to its much wider distribution in vowel space area.
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(a). Hakka monophthongs [i, e, a, o, u, ö(ii)]
produced by 18 males
(b). Hakka monophthongs [i, e, a, o, u, ö(ii)]
produced by 18 females
Figure 5 Vowel Space Areas Produced by Males and Females of Sixian Hakka
The tongue height difference in [i] and [u] is also supported across languages. In his
investigation of the first formant (F1) of [i] and [u] in 30 languages, de Boer (2010) found that the
mean F1 is higher for [u] than for [i] in 29 out of 30 languages. The F1 values of vowels are known to
be inversely related to tongue height, with open and close vowels having high and low F1 respectively
(Catford 2001; Fry 2001; Stevens 1998). Accordingly, [i] is made with a higher tongue position, and
results in longer VOT of stops, than [u]. Given the difference of vowel height in [i/u], [p]’s VOT in
[pi] should be, in principle, longer than that in [pu]. Why no significant difference of VOT existed in
[pi] and [pu] calls for further accounts. In fact, the effect of [i/u] difference is counterbalanced by the
co-articulation effect resulting from producing the rounded vowel [u]. Compared to [i], [u] is uttered
with lip protrusion which not only lengthens the vocal tract, but prolongs the lag of air release.19
This explains the non-significant difference in VOT between [pi] and [pu]. Nonetheless, one
question occurs in this line of reasoning. If the co-articulation effect resulting from the production
of [u] makes the VOT values in [pi] and [pu] statistically undifferentiated, why does there still exist
a significant VOT difference between [phi] and [phu]? The answer to the question lies in the VOT
length. When VOT is longer to a certain degree, for example, more than [t]’s VOT in this study,
then the co-articulation effect on VOT will be surpassed by the PoA effect. This accounts for the
reason why stops other than [p] explicitly realize the vowel height difference between [i] and [u].
Briefly, vowel height, rather than vowel frontness, plays a decisive role in the VOT production of
Hakka stops. Based on the preceding discussion, subsequent VOT studies should definitely take the
19 For more discussion of the co-articulation of lip rounding, please refer to Daniloff and Moll (1968).
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difference of vowel height between [i] and [u] into account, and take notice of the co-articulation
effect between [p] and [u].
Regarding speakers’ age and gender, different results were found in this study. As for gender,
there are physiological / anatomical differences between males and females (e.g., Cho and Ladefoged
1999; Docherty 1992; Titze 1994).20 However, the gender effect on VOT could not be statistically
distinguishable.21 This showed that speakers’ gender should not be regarded as a factor associated
with VOT variability. Regardless of non-significant VOT difference between different genders,
there actually emerged a pattern which reflected gender difference, as far as the VOT averages
were concerned. Compared with females, males articulated longer VOT in short-lag stops ([p]:
but shorter VOT in long-lag stops ([ph]: 52.1ms (M)/53.4ms (F), [th]: 54.9ms (M)/55.1ms (F), [kh]:
71.4ms (M)/ 73.5ms (F)). The phonetic VOT contrast between non-aspirated and aspirated stops was
comparatively larger in females than in males. It has been broadly documented in sociolinguistic
research (e.g., Coates 1993; Eckert 1996; Labov 2001; Lakoff 1975; Wodak and Benke 2001) that
females use clearer pronunciation, and speak in a more disciplined manner than males. Thus, the
difference in VOT between short-lag and long-lag stops produced by the two genders, though slight,
completely illustrated such sociolinguistic observations. Besides, it is reported that the perception
of more precise articulation of stops articulated by females is associative to longer VOT or wider
VOT difference between voiced stops and voiceless stops or between non-aspiration and aspiration
(Wadnerkar, Cowell, and Whiteside 2006; Whiteside, Hanson, and Cowell 2004; Whiteside and
Irving 1997; Whiteside and Marshall 2001).22 Undoubtedly, the result of this study well supports
20 Titze (1994) showed that the average vocal fold membranous length is 6 mm shorter in female adults than male adults. The shorter membranous length would increase the possibility of a more rapid closure gesture, resulting in the higher average fundamental frequency (F0) in female speech compared to male speech. Given that VOT is affected by the abduction speed of the vocal folds (Kewley-Port and Preston 1974), a gender bias between male and female plosives would be thus created.
21 Some readers may have a question in mind. If the gender factor did not reach a significant difference in VOT, why did the author need to discuss this issue? To this question, it should be claimed that not all linguistic changes should be statistically supported. For example, according to plenty of sociolinguistic and sociophonetics studies, there are “in-progress change” affected by social factors, like age, gender, educational background, socio-economic status, etc. The changes resulting from the social factors may not arrive at statistically significant difference; yet, it apparently shows a tendency that linguistic items change gradually with some social factors, say, gender or age. Hence, the lack of statistically significant difference in VOT should not preclude the discussion of this issue, especially when it showed a general changing tendency in terms of the gender factor (see Li (2013) for some discussion in this aspect).
22 Additionally, similar to speech rate, speech formality is also an influencing factor for the difference between males’ and females’ VOT lengths. Generally speaking, speakers will pronounce words clearly when speech situations are formal. In the present study, speech data were elicited by speakers’ reading and repeating a list of
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the sociolinguistic and perceptual view. In fact, the gender difference is also illustrated in the vowel
space patterns in Figure 5, with females’ larger than males’. Given this background of females’ VOT
production, how the foreign spouses in Hakka villages produced stops in Hakka (and Mandarin
Chinese) should be further scrutinized. Because of their diverse language backgrounds, they may
expand or reduce the VOT differences between aspirated and nonaspirated stops, and consequently
give rise to the learning difficulty of stops.
With regard to the age factor, there were significant VOT differences in short-lag and long-
lag stops among different age groups. By and large, the old produced shorter and more variable
VOT than the young and the middle-aged, particularly for long-lag stops (Morris and Brown 1987;
Neiman et al. 1983; Sweeting and Baken 1982). Specifically, the longer the VOT is, the more easily
the age effect reveals. This accounts for why statistically significant VOT differences only surface in
[k, ph, th, kh], but not in [p, t]. The VOT shortness in the aged may lie in the smaller lung volumes of
old speakers than those of other groups of speakers (Hoit, Solomon, and Hixon 1993). Additionally,
there is also reason to believe that the speech production time of elderly adults is relevant to lots of
physical and psychological changes associated with normal aging. For illustration, speech production
performance is influenced by cognitive and memory changes (Ulatowska 1985), and by physical
changes resulting from aging (Kahane 1981).23 Degeneration in the central nervous systems of
elderly adults may give rise to longer muscle contraction time, slower monosynaptic reflex time,
and so like (Kenney 1982; Valenstein 1981; Welford 1977; Whitbourne 1985). These aging and
degenerating processes in the aged are generally believed to give rise to a general slowing of neural
processing, and affecting sensory and motor performance abilities related to speech production (Kent
and Burkard 1981). Definitely, all these factors help clarify the shorter VOT values produced by the
old speakers in this study.
isolated syllables, a pretty formal means for data collection. For isolated syllables, the aerodynamic and articulatory differences between males and females are not great enough to create significant difference. This offers the reason for the slight VOT difference between males and females. If less formal methods (e.g., reading word pairs, reading texts, telling stories, casual conversation) are used for gathering data, larger gender differences in VOT can be expected. For related discussion of the gender factor in VOT, please refer to Morris et al. (2008).
23 Based on Kahane (1981), the physical changes of elderly adults include: (1) reduced biomechanical efficiency of the respiratory, laryngeal, and articulatory systems; (2) disturbances of motor and sensory innervation; and (3) mucosal and biochemical changes.
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6. Conclusion
To come to a conclusion, this study examined the effect of PoA, following vowel context,
speakers’ age and gender upon the VOT production of Hakka syllable-initial stops. Results indicated
that, except gender, all remaining factors influenced the VOT production of Hakka stops. This
indicated that controlling subjects’ gender in the VOT production, at least for isolated syllables, is
unnecessary in future related research. Yet, in spite of no significant VOT difference in genders, the
result still follows the general sociolinguistic observations that females are more serious in their
pronunciation than males. Finally, surveys like the present one, specific to one language/dialect,
are widely observed across languages, as stated in the introduction, so the present study provides a
general comprehension of the VOT issue in Hakka stops, represents an endeavor to bridge the gap in
the VOT studies of Hakka stops, and puts Hakka into the VOT array of world languages. Moreover,
it establishes a basis for mutual linguistic comparisons between Hakka and foreign languages,
especially for the increasing number of foreign spouses in Hakka villages.24
As already mentioned in section 2, VOT has been displayed to be influenced by complex
factors. Besides the factors explored in this study, future investigation should examine some other
factors, inclusive of word/non-word alternation, syllable position, utterance type (Baran et al.
1977), race (Ryalls and Zipper 1997), language experience (Flege and Eefting 1986), study design
differences (Ryalls and Zipper 1997), speech tempo and rate (Kessinger and Blumstein 1997, 1998;
Theodore, Miller, and DeSteno 2007), dialectal background (Schmidt and Flege 1996; Syrdal 1996),
and so like. In this way, a far further understanding of the VOT issue in Hakka stops can be achieved.
24 One reviewer suggested that more emphases should be put on how the foreign spouses learn Hakka. However, such discussion was not presented here for the following reasons. First, this study aimed only to provide a VOT reference norm for future studies. As is known, most foreign spouses learn Mandarin when moving to Taiwan, even in Hakka villages. Some of the foreign spouses actually learn Hakka, but the aim of the project and time limitation precluded the author from the time-consuming collection of speech data from the foreign spouses. Second, except for Mandarin, the application of acoustic analysis was scarcely seen in Hakka and Southern Min, both of which are not the mainstream dialects in Taiwan. For this reason, the reference norm must be established first; then following studies of related issues will be possible. Remarkably, using acoustic analysis in language teaching / learning frequently occurs in foreign students who learn Mandarin as a foreign or second language, like Cai and Gao (2002), Y. Lin and Wang (2005), Wen et al. (2009), Chung and Shi (2009), Zhuang and Guan (2009) and so on. Comparatively, Hakka is pretty under-investigated in this aspect, and, thus, calls for further endeavors.
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Acknowledgements
This study was financially sponsored by Hakka Affairs Council (Project No.: 100-03-01-02).
Thanks went to my two research assistants, Yu-Ching Huang and Li-Ping Fu, for their help with
speech data collection, VOT measurement, and statistical analysis. Besides, I also appreciated the
two anonymous reviewers for their insightful comments and constructive suggestions, most of which
were combined into this article. Of course, all remaining errors are mine.
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