STRESSED OUT WITH STRESS
Perceptual recognition
of acoustic correlates of stress in Tagalog
Sergey B. Klimenko
Maria Paz C. San Juan
Jem R. Javier
University of the Philippines
Unit 308, 137 Matatag St., Central,
Quezon City 1101
+63-905-331-8047
Translation Division, The Church
of Jesus Christ of Latter-Day Saints;
University of the Philippines
9 Linaluz St., San Carlos Heights,
Binangonan, Rizal
+63-928-503-1712
The Department of Linguistics
University of the Philippines
27 Geoffrey St., Gabriel Subd. II,
Hulong Duhat, Malabon City 1470
+63-923-295-2012
venom4000@gmail.com
venom_2000@mail.ru
sanjuanpc@ldschurch.org
ABSTRACT
Prosodic properties are features of human speech sound that can
be assigned to units larger than a segment like syllables and
phrases. Earlier studies have established that not all components
of the speech signal are perceived to be distinctive by speakerhearers. It is not enough therefore to establish the acoustic
correlates of “stress” if the same cannot be so identified through
simple hearing. This study aims to establish by experiment and
statistical methods the relative contribution of “stress” variables
(pitch, length, and intensity) in distinguishing one member of
minimal pairs or set from the other. Through GoldWave and
PRAAT programs, the variables are modified and sets of
synthesized utterances are evaluated by a sample of native
speakers. By comparing the results of this experiment with those
acoustic measurements the researchers intend to determine with
confidence the variable or combination of variables that dictates
what has been widely referred to as stress.
Keywords
Stress, acoustic correlates, pitch, intensity, duration, Tagalog
1. INTRODUCTION
Prosodic properties are features of human speech sound that can
be assigned to units larger than a segment like syllables and
phrases. Also termed suprasegmentals, these prosodic properties
are distinct in different languages as much as speech sound
patterns (Dobrovolsky and Czaykowska-Higgins, 2001).
This paper aims to establish by experiment and statistical methods
the relative contribution of “stress” variables (pitch, length, and
intensity) in distinguishing one member of minimal pairs or sets
from the other. Brichoux (1972: 6) believes that the phonemic
contrastiveness of stress placement in Tagalog, if not in many
Philippine-type languages, “deals only with a subjective
phenomenon based on auditory impressions or native reaction.”
This is the reason why he differentiates the two classic definitions
of stress as (1) perceived prominence of a syllable within a word,
judged by the native speakers; and (2) as Ladefoged (2003: 90)
aptly states: “the auditory/acoustic consequences of a syllable
jemroquejavier@gmail.com
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having received stress…[which] are likely to be some
combination of increased pitch, length, and loudness, with the first
two playing the greatest roles.”
2. SOME STRESSFUL STUDIES
For many decades now, linguists have still been debating on the
nature of stress. Bloomfield (1917) defines this (and he uses the
word ‘accent’) as involving greater stress and higher pitch.
Furthermore, as he describes the stress of the English language,
Bloomfield (1933) distinguishes the stressed syllable as the one
being pronounced louder than the other syllables within a word.
Pike (1947: 250) agrees with this claim, stating that stress is “a
degree of intensity upon some syllable which makes it more
prominent or louder than an unstressed syllable.” Nyqvist (1962)
says essentially the same thing: that what sets a stressed syllable
apart from the unstressed one/s is the greater loudness of the
stressed syllable.
On the other hand, there are also linguists such as Berger (1955)
who suppose that intensity or loudness may not be the main
contributor of stress. He suggests that “a sound may be more
prominent…by timbre, length, or articulatory energy without
being louder in any physical sense.” Fischer-Jørgensen (1961)
agrees with Berger and even goes farther by stating that intensity
may be a trivial factor in the definition of stress. The claims made
may be because the definition of stress in the past had been based
on the studies made on the English language. Fischer-Jørgensen
(1961: 133) suggests that to really find the acoustic correlates of
stress, “it would be of great interest to undertake studies of stress
in different languages.”
As a reply to Fischer-Jørgensen’s challenge of studying different
languages to firmly establish the definition of stress, Brichoux
(1972) studies the spectrographic acoustic correlates of stress in
Tagalog, i.e., the relative amplitude (or loudness or intensity),
relative frequency (or pitch), and relative length (or duration) of
the said language. Using a tape recorder and the Sonagraph
(trademark and name used by the Kay Elemetrics Company for
their sound spectrograph), Brichoux finds out that amplitude is not
what signals the stress in Tagalog:
“Acoustically speaking, it may very well be
that stress will always be found to consist in a
number of factors, of which intensity may be
one, but certainly not demonstrably the most
important, factor. Stress is a universal when
all levels of language are considered, but its
acoustic parameters may be better described
as bundles of ‘features’: intensity, relative
frequency,
duration,
vowel
quality
(envelopes), or degree and kind of change in
one or some of these phenomena.” (Brichoux,
1972: 18-19)
Brichoux (1972) also calls for research studies using synthetic
speech in order to determine which acoustic correlates are
perceived by listeners as stress; this challenge is what stimulates
the researchers to undertake this research.
Before the publication of Brichoux’s 1972 study on the acoustic
correlates of stress in Tagalog, Gonzalez (1970) has already
studied the acoustic correlates of accent, rhythm (syllable
duration), and intonation (syntactic accent) in the same language.
Using Pitch Extractor and Trans-Pitchmeter, computer programs
written at the Phonology Laboratory of the University of
California in Berkeley, Gonzalez discerns that it is the higher
fundamental frequency (pitch), greater amplitude, and longer
duration that acoustically signal the accent in Tagalog. However,
for Gonzalez (1970: 556), the three acoustic correlates may not
always be present all at the same time: “the speaker at times uses
only one of three correlates in the actual phonetic realization of
his utterances, thus showing the phenomenon of ‘trading effect.’”
Another groundbreaking study was made by Tsukenazu
Moriguchi in his 1977 study entitled, “Some remarks on Tagalog
stress: Physical accents vs. psychological accents.” According to
this study, only duration functions as a phoneme. Furthermore,
the stressed syllable is “(1) the one preceded by a syllable with
short duration, or (2) the syllable in the initial position, if all
syllables are equal in duration.” (p. 79)
multitrack audio/video mixing software. The company is named
after the GoldWave Digital Audio Editor, which was released in
April 1993. GoldWave has been used for historic recording
analysis in the moon landing, as reported on BBC and the
Houston Chronicle. It is used in dozens of schools and
universities around the world and is mentioned in numerous
research papers covering a wide variety of topics, including
neuropsychology, bioacoustic signals, seismic analysis, and
engine and animal identification. GoldWave is very accessible
and has become popular in the visually impaired community and
has applications for the study of hearing impairment and
perception. [About GoldWave (GoldWave, 2010)]
3.3 (Par)oxytonic Words Measured
The study focuses on the analysis of stress in Tagalog minimal
pairs in isolation. The informant (33 years old, native resident of
Metro Manila and native speaker of Tagalog) was asked to
pronounce in triplets twelve pairs of Tagalog disyllabic words
which phonologically differ only in their stress position:
(1) aso: ['Ɂʌ.sɔ] ‘dog’ – [Ɂʌ.'sɔ] ‘soot’
(2) balat: ['bʌ.lʌt] ‘birthmark’ – [bʌ.'lʌt] ‘skin’
(3) bukas: ['bʊ.kʌs] ‘tomorrow’ – [bʊ.'kʌs] ‘open’
(4) gabi: ['gʌ.bɪ] ‘taro’ – [gʌ.'bɪ] ‘night’
(5) gutom: ['gʊ.tɔm] ‘hunger’ – [gʊ.'tɔm] ‘hungry’
(6) hamon: ['hʌ.mɔn] ‘challenge’ – [hʌ.'mɔn] ‘ham’
(7) hapon: ['hʌ.pɔn] ‘afternoon’ – [hʌ.'pɔn] ‘Japanese’
(8) pako: ['pʌ.kɔɁ] ‘nail’ – [pʌ.'kɔɁ] ‘species of medicinal plant’
(9) paso: ['pʌ.sɔɁ] ‘burn’ – [pʌ.'sɔɁ] ‘flower pot’
(10) puno: ['pʊ.nɔɁ] ‘tree’ – [pʊ.'nɔɁ] ‘full’
(11) saya: ['sʌ.jʌ] ‘dress’ – [sʌ.'jʌ] ‘happy’
(12) tubo: ['tʊ.bɔ] ‘tube’ – [tʊ.'bɔ] ‘sugar cane’
The pairs of Tagalog disyllabic words which differ in stress
placement were taken from Ramos’s 1971 study on Tagalog
structures.
With the view of measurement and further
manipulation only middle members were taken into consideration
in every triplet. Duration, pitch, and intensity of both vowels in
every word were measured with the help of Praat (see Figure 1).
3. DATA AND ANALYSES
3.1 Praat
Praat is computer software developed by Paul Boersma and David
Weenink of the Institute of Phonetic Sciences, University of
Amsterdam. The program aids the users in investigating a large
number of processes such as:
(1) making spectrograms;
(2) making pitch analyses;
(3) looking at how the ear analyzes sounds;
(4) synthesizing speech in articulatory terms;
(5) using neural nets; and
(6) describing phonetic events by means of
optimality theory; among others (Ladefoged,
2003: 84).
3.2 GoldWave
GoldWave is computer software manufactured by GoldWave Inc.
a privately owned, Canadian based corporation. GoldWave offers
affordable, professional quality, digital audio editing software and
Figure 1: Sound wave and spectrogram of ['Ɂʌ.sɔ] in Praat.
The measurements are given in the following table:
Table 1. Measurements of duration, pitch, and intensity
on the words elicited.
WORD
DUR1
(ms)
DUR2
(ms)
PITCH1
(Hz)
PITCH2
(Hz)
INT1
(dB)
INT2
(dB)
DUR2
(ms)
PITCH1
(Hz)
['Ɂʌ.sɔ]
144
211
[Ɂʌ.'sɔ]
54
218
['bʌ.lʌt]
161
[bʌ.'lʌt]
169 ms, respectively. The mean values of duration for stressed
and unstressed penult vowels are around 127 ms and 49 ms,
respectively. Please see graph below:
PITCH2
(Hz)
INT1
(dB)
INT2
(dB)
123
85
83
67
87
100
75
75
117
120
90
88
83
47
125
81
103
77
85
0.12
['bʊ.kʌs]
106
140
128
110
79
88
0.10
[bʊ.'kʌs]
46
155
82
113
65
85
0.08
['gʌ.bɪ]
133
264
104
82
83
71
[gʌ.'bɪ]
51
267
89
98
75
78
['gʊ.tɔm]
108
99
119
105
79
82
[gʊ.'tɔm]
40
91
91
115
66
77
['hʌ.mɔn]
112
123
136
116
86
77
[hʌ.'mɔn]
67
122
104
127
78
80
['hʌ.pɔn]
117
84
130
94
86
69
[hʌ.'pɔn]
53
132
96
119
75
77
['pʌ.kɔɁ]
109
134
110
90
85
76
[pʌ.'kɔɁ]
34
128
85
104
71
78
['pʌ.sɔɁ]
140
131
134
76
87
71
Intensities in dB of the First and Second Syllables
of the 12 Minimal Pairs
Density
DUR1
(ms)
WORD
0.04
0.02
0.00
65
70
75
80
85
90
Data
INT1 and INT2, intensities of the first and second syllables of the 12 paroxytonic words
INT3 and INT4, intensities of the first and second syllables of the 12 oxytonic words
Figure 2. Histogram of intensity.
Pitches in Hz of the First and Second Syllables
of the 12 Minimal Pairs
0.06
43
145
87
120
70
82
['pʊ.nɔɁ]
151
144
136
98
77
74
0.04
[pʊ.'nɔɁ]
58
149
85
116
69
79
['sʌ.jʌ]
133
274
133
78
87
79
[sʌ.'jʌ]
65
291
98
116
78
85
['tʊ.bɔ]
121
246
140
92
76
72
[tʊ.'bɔ]
34
205
98
105
70
76
Density
[pʌ.'sɔɁ]
Variable
PITCH1
PITCH2
PITCH 3
PITCH 4
Mean StDev N
126.1 11.13 12
93 12.45 12
90.25 7.225 12
111.3 9.089 12
0.03
0.02
0.01
0.00
80
100
120
140
Data
PIT1 and PIT2, pitches of the first and second syllables of the 12 paroxytonic words
PIT3 and PIT4, pitches of the first and second syllables of the 12 oxytonic words
Figure 3. Histogram of pitch.
It can be seen from the graphs that the mean of DUR1 is less than
DUR2 but DUR1 is more compact and DUR2 more dispersed.
The same pattern can be seen from DUR3 and DUR4 graphs.
Furthermore, DUR2 and DUR4 appear to be almost identical.
These are the patterns that Moriguchi (1977) has hypothesized
regarding duration when he talked about the Tagalog stress. See
Figure 4.
Durations in Milliseconds of the First and Second Syllables
Pitch, showing more regularity, is higher on the stressed vowel
than on the unstressed one in all words, paroxytonic and oxytonic.
The mean difference in pitch between two syllables is about -33
Hz for paroxytonic and about +21 Hz for oxytonic words. See
Figure 3 below.
of the 12 Minimal Pairs
0.04
Variable
DUR1
DUR2
DUR3
DUR4
0.03
Density
Duration exhibits somewhat more sophisticated pattern: while
length of the ultima vowel in both words in most of the pairs
shows considerable degree of uniformity, length of the penult
vowel in oxytonic words is significantly shorter than that of the
penult vowel in paroxytonic words. The mean values of duration
for unstressed and stressed ultima vowels are around 163 ms and
Mean StDev N
83 4.221 12
75.75 6.312 12
72.42 4.522 12
79.75 3.646 12
0.06
0.05
Intensity manifests the least clear pattern for paroxytonic and
oxytonic words. The ultima vowel has stronger intensity relative
to that of the penult vowel in all oxytonic words but [Ɂʌ.'sɔ] in the
case of which intensity of both the vowels is the same (75 dB).
The penult vowel has stronger intensity relative to that of the
ultima vowel in ten out of the twelve paroxytonic words. In
['bʊ.kʌs] and ['gʊ.tɔm] the unstressed vowel is louder than the
stressed one (79 db vs. 88 dB, and 79 dB vs. 82 dB, in ['bʊ.kʌs]
and ['gʊ.tɔm], respectively). The mean difference in intensity
between two syllables is about -9.1 dB for paroxytonic words
(exclusive of ['bʊ.kʌs] and ['gʊ.tɔm]), and about +14.8 dB
(exclusive of [Ɂʌ.'sɔ]) or +13.5 dB (inclusive of [Ɂʌ.'sɔ]) in
oxytonic words.
Variable
INT1
INT2
INT3
INT4
Mean StDev N
127.9 18.44 12
163.9 66.41 12
49.33 10.81 12
169 62.26 12
0.02
0.01
0.00
50
100
150
200
Data
250
300
DUR1 and DUR2, durations of the first and second syllables of the 12 paroxytonic words
DUR3 and DUR4, durations of the first and second syllables of the 12 oxytonic words
Figure 4. Histogram of duration.
Thus, the initial data reveal the following: (1) there is a
correlation between duration and stress in every case, with
stressed penult vowel being notably longer than unstressed penult
vowel, and unstressed and stressed ultima vowels being of
relatively the same duration; (2) there is a strong one-to-one
correlation between pitch and stress, with pitch of stressed vowel
being higher than that of unstressed one, irrespective of their
position in a word; and (3) there is somewhat loose correlation
between intensity and stress, with intensity of stressed vowel
being acoustically stronger than that of unstressed one,
irrespectively of their position, only in nine of 12 pairs; in the
remaining three pairs, one of the words does not show any
correlation between intensity and stress.
To determine by statistical methods if the stress variables
(duration, pitch and intensity) manifest significant correlation with
stress, the paired T-test in Minitab was employed. Minitab is a
“statistics package” developed by Barbara F. Ryan, Thomas A.
Ryan, Jr., and Brian L. Joiner of the Pennsylvania State University
in 1972 (Meyer and Krueger, 2004). After the statistical tests it
can be concluded that stress variables are significant and therefore
have important contribution to the perception of stress if the PValue associated with the computed T-Value is equal or less than
0.05.
Below are the results of the paired t-tests for duration, pitch and
intensity.
Table 2. Paired t-test results
for duration, pitch and intensity
for the 12 paroxytonic words
Stress Variable
Mean
P-Value
0.082
Duration
Penult
127.7 ms
Ultima
163.9 ms
0.000
Pitch
Penult
126.08 Hz
Ultima
93.00 Hz
0.009
Intensity
Penult
83.00 dB
Ultima
75.75 dB
.
From the P-Values above it can be seen that both pitch and
intensity manifest significant correlation with stress.
Furthermore, pitch and intensity tend to be higher on the penult,
where the stress is, rather than the ultima, for the given set of
paroxytonic words.
The current data however, do not show enough proof that duration
is significant at 0.05. Going back to the raw data it is noticeable
that there is no consistent pattern in duration unlike what can be
seen in pitch and intensity. However, it is too early to discount
the effect of duration in the perception of stress at this point
because although duration is not significant at alpha=0.05, it is
significant at alpha=0.10.
Table 3. Paired T-test results
for duration, pitch and intensity
for the 12 oxytonic words
Stress Variable Mean
P-Value
Duration
Penult
Ultima
Pitch
Penult
Ultima
Intensity
Penult
Ultima
0.000
49.3 ms
169.0 ms
0.000
90.25 Hz
111.33 Hz
0.001
72.42 dB
79.75 dB
For the 12 oxytonic words, results show that duration, pitch, and
intensity very clearly manifest significant correlation with stress.
Duration, pitch, and intensity show a strong consistent pattern to
be higher in value in the stressed syllable, the ultima. Among the
three variables, duration shows the most distinct pattern. Duration
on the stressed syllable on the average is 2.42 times more than the
unstressed syllable while pitch and intensity is only about 0.26
and 0.11 respectively.
Having obtained these facts, the following hypothesis, consisting
of three suppositions, can be formulated: (1) stress falls on
ultimate vowel if that vowel is preceded by a relatively shorter
one and it falls on the penult vowel if that vowel has a duration as
long as the ultima; (2) pitch is of secondary significance for stress
in Tagalog, or else tends to be higher on stressed vowel, but is not
significant for stress (the assumption that being stressed for a
Tagalog vowel necessarily means having relatively higher pitch
would be implausible, since pitch is operative in intonation
patterns formation, and it will differ for the same words
pronounced as a question, exclamation, etc., which are not
represented in this study); and (3) since there are minimal pairs
that do not differ in intensity pattern, stress is of loose dependence
on intensity, i.e., intensity may also be of secondary significance
just like the pitch. Note that the first part of the hypothesis is in
tune with the stand of Moriguchi’s 1977 study on stress in
Tagalog.
3.4 Sound Synthesis
The The files used in the perception test were prepared with the
help of the Praat toolkit and the GoldWave software. For the
purpose of sound modification, the researchers took the first word
(paroxytonic) of each pair, and adjusted alternately its duration,
pitch, and intensity (the former two were manipulated in Praat,
while intensity in GoldWave).
For each of the stress correlates, the value of the penult vowel in
the first (paroxytonic) word was modified to the value of the
penult vowel in the second (oxytonic) word. The value of the
ultimate vowel in the first (paroxytonic) word was modified to the
value of the ultimate vowel in the second (oxytonic) word. While
an individual stress correlate is modified, the other two are kept
intact. For instance, the word ['Ɂʌ.sɔ] in terms of duration was
manipulated in such a way that the length of the penult vowel
(144 ms) in the paroxytonic word was changed to 54 ms (duration
of the penult vowel of the oxytonic word), and that of the ultimate
vowel (211 ms) in the paroxytonic word to 218 ms (duration of
the ultimate vowel in the paroxytonic word), while the pitch and
intensity of the vowels in this word were left unmodified (Fig. 2
and Fig. 3).
By this the researchers intended to single out significance of each
separate correlate for stress recognition during the perception test
conducted later: if a paroxytonic word with a modified acoustic
property is perceived or “heard” as an oxytonic word of the same
pair, then this property is to be considered significant for stress.
To determine if the acoustic correlate is perceived or heard by the
respondents, they must have noticed a change in the meaning of
the word. As a result of the data manipulation stage of this study,
for each minimal pair three files of every modified paroxytonic
word were obtained: one for each of manipulated duration, pitch,
and intensity.
21
3
Ilokano
1
Hiligaynon
3
43
1
Kapangpangan
1
Ilokano
1
Total
51
Pangasinan
1
Kapangpangan
1
Tagalog
37
Tagalog
33
Total
51
Total
51
Distribution of the Native Languages
Spoken by the 51 Respondents in the Sample
Bicol Chabacano
English
Fookien
Hiligaynon
Ilokano
Kapangpangan
Pangasinan
Category
Bicol
Chabacano
English
Fookien
Hiligaynon
Ilokano
Kapangpangan
Pangasinan
Tagalog
Tagalog
Figure 7. Pie graph of the native languages
of the respondents.
Figure 5. ['Ɂʌ.sɔ] on the pitch and duration
manipulation screen of Praat.
The answers were tabulated and analyzed using paired T-test in
MiniTab. The researchers ran the test in three batches: Batch 1,
for all the respondents in the sample (n=51); Batch 2, for those
whose native and home language is Tagalog (n=29); and Batch 3,
per minimal pair for the respondents who correctly identified both
the unaltered sounds. For example, paired T-test was computed
for the minimal pair (['bʌ.lʌt] ‘birthmark’ – [bʌ.'lʌt] ‘skin’) using
only the responses from the 48 respondents who correctly
identified the unaltered pair during the survey, for the pair
(['hʌ.mɔn] ‘challenge’ – [hʌ.'mɔn] ‘ham’) 29 respondents and so
on. Only the minimal pairs (['Ɂʌ.sɔ] ‘dog’ – [Ɂʌ.'sɔ] ‘soot’) and
(['pʌ.sɔɁ] ‘burn’ – [pʌ.'sɔɁ] ‘flower pot’) were correctly identified
by all respondents.
The summary of the results of the paired T-tests is below:
Figure 6. Manipulating intensity using GoldWave.
Table 5. Paired T-test results
Respondents
3.5 Perceptual experiment
Fifty-one students of the University of the Philippines from 34
towns and cities around the archipelago participated in the
perceptual experiment. Below are some important details about
the respondents:
Native
Language
n=
Balat
aso
hamon
bukas
gabi
Table 4. Profile of the respondents
First
Language
at Home
Batch 1
All respondents
(n-51)
Minimal Pairs
Sex
n=
Age
n=
n=
F
40
16
8
Bicol
2
Bicol
1
M
11
17
11
Chabacano
1
Cebuano
1
Total
51
18
14
English
4
Chabacano
1
19
9
Fookien
1
English
8
20
5
Hilgaynon
3
Fookien
2
gutom
tubo
hapon
Significant Stress Correlates
and their P-Values
duration*
pitch (0.024)
duration*
pitch (0.024)
duration (0.006)
pitch (0.002)
duration*
duration*
pitch (0.024)
duration*
pitch (0.001)
duration*
intensity (0.010)
pitch*
duration (0.051)
intensity (0.032)
pitch (0.007)
Respondents
Minimal Pairs
pako
paso
puno
saya
Batch 2:
Tagalog
as the only
mother tongue
and
language at home
(n-29)
Balat
aso
hamon
bukas
gabi
gutom
tubo
hapon
pako
paso
puno
saya
Batch 3:
Respondents
who correctly
answered
on both minimal
pairs
balat (n=48)
aso (n=51)
hamon (n=29)
bukas (n=29)
gabi (n=29)
gutom (n=29)
tubo (n=29)
hapon (n=47)
pako (n=50)
paso (n=51)
puno (n=50)
saya (n=50)
Significant Stress Correlates
and their P-Values
duration*
duration*
duration*
pitch*
duration*
pitch (0.013)
duration*
duration*
duration (0.032)
duration*
duration*
duration*
pitch (0.32)
duration*
intensity (0.030)
pitch (0.023)
--duration*
duration*
duration (0.001)
pitch (0.003)
duration*
pitch (0.023)
duration*
pitch (0.024)
duration*
pitch (0.024)
duration (0.019)
pitch (0.003)
duration*
duration*
pitch (0.044)
duration*
pitch (0.001)
duration*
pitch (0.003)
duration (0.051)
pitch (0.024)
duration*
duration*
duration*
pitch*
duration*
pitch (0.013)
* P-Value= 0.000
4. FURTHER INTERPRETATIONS
The data obtained by the measurements can be used for building
hypotheses on the subject matter, i.e., what acoustic features of
vowels are relevant for stress in Tagalog words.
In the perception experiment, intensity is significant only for the
minimal pairs (['tʊ.bɔ] ‘tube’ – [tʊ.'bɔ] ‘sugar cane’) and
(['hʌ.pɔn] ‘afternoon’ – [hʌ.'pɔn] ‘Japanese’) among Batches 1
and 2 but not among Batch 3.
It is also interesting to point out that in the perception experiment,
the respondents whose native and home language is Tagalog
perceived the change in stress less when pitch was changed than
do the non-native Tagalog speakers. The native Tagalog speakers
collectively did not perceive the change in stress when pitch was
changed in the following five minimal pairs: ['bʌ.lʌt] ‘birthmark’
– [bʌ.'lʌt] ‘skin’, ['Ɂʌ.sɔ] ‘dog’ – [Ɂʌ.'sɔ] ‘soot’, ['hʌ.mɔn]
‘challenge’ – [hʌ.'mɔn] ‘ham’, ['gʌ.bɪ] ‘taro’ – [gʌ.'bɪ] ‘night’, and
['hʌ.pɔn] ‘afternoon’ – [hʌ.'pɔn] ‘Japanese’, while the non-native
Tagalog respondents did.
In the perception experiment, duration was shown to be the most
significant among the three variables of stress. This is true for all
the minimal pairs except for (['hʌ.pɔn] ‘afternoon’ – [hʌ.'pɔn]
‘Japanese’). Pitch comes in second in significance. This variable
is significant in 4 out of 12 minimal pairs as perceived by the 29
respondents whose native and home language is Tagalog (Batch
2) and 9 out of 12 of the minimal pairs as perceived by all of the
respondents and by those who correctly recognized the minimal
pairs (Batches 1 and 3).
In the analysis of the stress components of the minimal pairs and
the results of perception experiment duration has shown the most
significant contribution in the perception of stress and pitch
second. Although statistical tests show all three stress variables
are significant, the perception experiment validated only duration
and pitch.
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