This document provides a literature review on descriptions of the Hanoi Vietnamese and General American English monophthong systems. It discusses the inconsistent descriptions of some Hanoi Vietnamese monophthongs like ư and ơ in the literature due to differences in phonetic vs. phonological goals and acoustic similarities between features. It summarizes Thompson's (1965) description of the Hanoi Vietnamese vowel system as consisting of upper and lower subsystems. The review then discusses acoustic description attempts and formant analysis for characterizing vowel qualities. Finally, it provides an overview of the traditional and acoustic descriptions of monophthongs in General American English.

1. i
Vietnam national university, Hanoi
University of languages and international studies
Faculty of Post graduate studies
DOÃN MINH MÃO
A comparative acoustic study of Hanoi
Vietnamese and general American
English monophthongs
Ph©n tÝch ©m häc so s¸nh hÖ thèng nguyªn ©m ®¬n TiÕng ViÖt Hµ Néi vµ tiÕng Anh
Mü Phæ th«ng
A thesis submitted to the Faculty of Post Graduate Studies,
University of Languages and International Studies, VNU, Hanoi
in partial fulfillment of the requirements for the degree of
Master of Arts
in
English Linguistics
Code: 60.22.15
HA NOI – 2012

2. ii
Vietnam national university, Hanoi
University of languages and international studies
Faculty of Post graduate studies
DOÃN MINH MÃO
A comparative acoustic study of Hanoi
Vietnamese and general American
English monophthongs
Ph©n tÝch ©m häc so s¸nh hÖ thèng nguyªn ©m ®¬n TiÕng ViÖt Hµ Néi vµ tiÕng Anh
Mü Phæ th«ng
A thesis submitted to the Faculty of Post Graduate Studies,
University of Languages and International Studies, VNU, Hanoi
in partial fulfillment of the requirements for the degree of
Master of Arts
in
English Linguistics
Code: 60.22.15
Supervisor: Pham Xuan Tho, M.A.
HA NOI – 2012

3. vi
LIST OF TABLES
Table Title Page
1 The first and second formant frequencies of all the subjects for
each vowel.
34
2 The values of the first and the second token of each sound
produced by each speaker.
47
3 The average values of F1 and F2 for each vowel as spoken by
ten speakers
53

4. vii
LIST OF FIGURES
Figure Title Page
1 The spectrogram of the author’s pronunciation of [i] in hi 18
2 The effect of [ɲ] on [i] in inh and nhi, as produced by the
researcher.
34
3 The effect of [ɲ]on [a] in nha 36
4 The difference between the vowel in e and anh, produced by a
subject.
38
5 The difference between the vowel in e and anh,
produced by another subject.
38
6 The similarities between the vowel in anh and ay,
produced by a subject.
39
7 The similarities between the vowel in anh and ay,
produced by another subject
39
8 Spectrograms of [ɤ]and [ɤ̆n] 41
9 Spectrograms of [ɤn], on the left, and [ɤ̆n], on the right 42
10 The similarities between the vowel in a [a] and ay [ăi],
produced by a subject. The spectrogram of [a] is on the
left, and of [ăi] is on the right.
44
11 The duration of [a] and [ă] in ai, on the left, and ay, on
the right.
45
12 The correlation between the two measurements of each F1 and
F2 by the first 4 subjects.
50
13 The monophthongs of ten speakers of Vietnamese in Hanoi
dialect
53
14 The formant chart showing the average values of F1 and F2
for each monophthong as spoken by ten speakers
54
15 A formant chart showing the formant frequency F1 and F2 for
eight English monophthongs. The scales are marked in Hz,
arranged at Bark scale intervals
56
16 The formant chart of Vietnamese monophthongs produced by
female speakers
57
17 The formant chart of General American English monophthongs
produced by female speakers
58

5. viii
TABLE OF CONTENTS
STATEMENT OF AUTHORSHIP ................................................... i
ABSTRACT................................................................................... iv
ACKNOWLEDGEMENT................................................................ v
LIST OF TABLES ......................................................................... vi
LIST OF FIGURES....................................................................... vii
TABLE OF CONTENTS.............................................................. viii
Chapter 1: INTRODUCTION.......................................................... 1
1. Rationales ................................................................................................................... 1
2. Scope of the research and the research questions................................................... 3
Chapter 2: THE REVIEW OF LITERATURE ................................. 5
2.1. The articulatory description of Hanoi Vietnamese monophthongs ....................... 5
2.2 The acoustic description attempts............................................................................ 10
2.3. Characterizing vowel qualities with the acoustic properties................................ 16
2.4 General American English........................................................................................ 24
2.4.1 The traditional description ................................................................................ 24
2.4.2 The acoustics of GA........................................................................................... 27
Chapter 3 RESEARCH METHODOLOGY.....................................30
3.1 The subjects ............................................................................................................... 30
3.2 The stimuli ................................................................................................................. 30
3.3 The recording process ............................................................................................... 31
3.4 The analysis process.................................................................................................. 32
Chapter 4: FINDINGS AND DISCUSSION ..................................34
4.1 The acoustics of Hanoi Vietnamese monophthongs .............................................. 34
4.1.1 [ɛ̆] and [ɛ] .......................................................................................................... 35
4.1.2 [ɤ] and [ɤ̆] ........................................................................................................... 40
4.1.3 [a] and [ă]............................................................................................................ 43

6. ix
4.1.4 Regression analysis............................................................................................ 48
4.1.5 Charting the formants of Hanoi Vietnamese monophthongs ........................ 51
4.2 The monophthongs of Hanoi Vietnamese and General American English in
comparison ....................................................................................................................... 58
Chapter 5 CONCLUSION ..............................................................62
5.1. The main findings on the acoustics of Hanoi Vietnamese monophthongs ......... 62
5.2 The monophthongs of Hanoi Vietnamese and General American English in
comparison ....................................................................................................................... 63
5.3 The limitations of the study and suggestions for further research. ...................... 64
REFERENCES...............................................................................66
Appendix 1: Phiếu chấp thuận tham gia vào nghiên cứu ...................................................... 68
Appendix 2: The stimuli ........................................................................69

7. 1
Chapter 1: INTRODUCTION
1. Rationales
The ultimate aim of this research is to achieve a cross language
comparison between the acoustic properties of Hanoi Vietnamese
monophthongs and General American English monophthongs. The
findings of the accomplished study are significant, from both the
linguistic and pedagogical perspectives.
Ladefoged states firmly that, “The best way of describing vowels is
not in terms of the articulations involved, but in terms of their
acoustic properties.” (2003, p.104). A considerable amount of space
of this thesis is devoted to the researcher’s analysis of the
monophthongs, or pure vowels (Wells, 1962, p.1) of Vietnamese,
Hanoi dialect. Aside from a few studies conducted overseas, which
have important limitations to be addressed, which are discussed in
details in the Review of Literature of this thesis, there has been no
attempt to study the vowel acoustics of the recognized standard
Vietnamese so far.
The literature on Vietnamese vowel acoustics has been mainly
concerned with the description of the sounds from the views of
articulatory phonetics. The investigations conducted by Nguyễn
(1998), and Đoàn (2000) are typical examples. These studies
examined the behaviors of the vocal organs involved in the
articulatory process when a particular sound is being produced. This
method, while having the advantage of being straightforward, has put

8. 2
forwards ideas which remain an approximation to the truth.
Ladefoged and Johnson (2011, p.197) comment,
Traditional articulatory descriptions are often not in accord with
the actual articulatory facts. For well a hundred years,
phoneticians have been describing vowels in terms such as high
versus low and front versus back. To some extent, they have been
using these terms as labels to specify acoustic dimensions rather
than as descriptions of actual tongue positions. Phoneticians are
thinking in terms of acoustic fact, and using physiological fantasy
to express the idea.
Acoustics offers sufficient tools for explaining the vowel qualities.
The production of a speech sound involves firstly the vibration of the
vocal cords, which produces sound waves. It involves secondly the
performance of the vocal tract, which can be changed into various
shapes, as a filter, under the acoustic impedance. Vowel sounds are
characterized acoustically by formants, which are frequency regions
of high energy concentration corresponding to the pass bands of the
throat and mouth cavities (Wells, 1962, p.1).Therefore, instead of
only studying a particular sound from the outside, rather
subjectively, by observing with eyes, trying to set up a collection of
its articulatory features, there should be a rigorous description
method where every dimension of a sound as its nature is measured
and displayed objectively on the screen of an electronic device.
The analysis, carrying out appropriately, would result in an acoustic
vowel chart, representing accurately the linguistic aspects of Hanoi

9. 3
Vietnamese monophthongs, which serves as a valuable source of
reference for cross language comparison.
The pronunciation of General American English and of Hanoi
Vietnamese are acknowledged as the reference accents of English
and Vietnamese respectively. As a result, from the pedagogical
aspect, the findings of the research are of highly practical values in
teaching the pronunciation of one language to learners of the other
language.
2. Scope of the research and the research questions
The study first examined the quality of the pure vowels in Hanoi
Vietnamese. The frequencies of each of the first two formants of
each monophthong (F1, F2) were investigated on the acoustic
spectrographs, generated from the speech analyzer program PRAAT.
The results obtained from the analysis were then compared with the
results of a recent research in the monophthongs of General
American English, conducted by Clark, M. J, Hillenbrand, J, et al.
(1995).
The research is aimed at answering two questions:
1) What are the acoustic properties characterizing Hanoi Vietnamese
monophthongs?

10. 4
2) What are the common and distinctive features between the
relative positions of the monophthongs in Vietnamese and General
American English on the formant charts?

11. 5
Chapter 2: THE REVIEW OF LITERATURE
2.1. The articulatory description of Hanoi Vietnamese
monophthongs
There have been considerable attempts to give a description of the
vowel system of Hanoi Vietnamese, impressionistically and
acoustically. This part of the review of literature is concerned firstly
with the set of Vietnamese monophthongs in Hanoi dialect, the
description of which has generated a great amount of debate among
phoneticians. I shall then give an examination of the second set,
being described with fair consistency.
As mentioned above, the vowel inventory of Vietnamese includes
some monophthongs that have been described consistently in the
literature; they also have transparent orthographic representation:
i/i/, u/u/, ô/o/, o/ɔ/, ê/e/, e/ε/, a/a/. However, for some other
monophthongs, orthographically realized by ư, ơ, â, and ă, there are
important conflictions in description. For example, Lindau (1978), as
cited in Matt (2009) describes ư as high back unrounded, while
Thompson (1965) insists that it is high central unrounded, or as and
high central, as proposed by Pham (2003). Hwa-Froelich (2002), as
cited in Matt (2009), puts forward the suggestion that ư that includes
/ɯ/ and /ʊ/, is characteristically employed to denote a high back
unrounded and a lower-high back rounded vowel, respectively.
Lindow (1978) has identified ơ as being back unrounded, /ɤ/ or /ʌ/,
while according to Thompson (1965), it should be represented by /ə/.

12. 6
According to Matt, Alina, and Alison (2009) there are two reasons
for the inconsistency in the description of ư and ơ. Firstly, the
acoustic distinction between lip-rounding and the backness of the
tongue is not clear. The traditional analysis of spectrogram cannot
convincingly differentiate the characteristics because of the almost
similar, or even equal acoustic properties (Ladefoged, 2011). The
second reason is the different goal behind the phonetic and
phonological descriptions of the vowels concerned. Phonetic
descriptions, the goal of which is to provide a description of the
vowels’ features as being realized in spoken speech, are concerned
with the articulatory or acoustic features of the vowels. Phonological
descriptions, on the other hand, are concerned with the vowels’
structure and function in relation to each other in a system.
Naturally, different goals of the studies conducted have resulted in
the inconsistency.
As mentioned earlier, there are two other Vietnamese vowels, which
have been identified with conflicting features. The vowels realized
by â and ă are traditionally described as “short”, low central.
However, there has been a great amount of debate surrounding
whether these vowels are short counterparts of ơ and a respectively,
which are long vowels of similar quality, or they are short vowels
with distinct vowel qualities. One of the ultimate goals of the current
study is to provide a systematic description of the quality of Hanoi
Vietnamese pure vowel inventory; therefore, it shall not be
concerned with the vowel duration.

13. 7
Thompson (1965) is among the references of highest citation
frequency. In his rather comprehensive account of the Vietnamese
language, a fine amount of space has been devoted to the vowel
system of Hanoi dialect.
According to Thompson (1965), the dialect’s vocalic system consists
of two sub-systems of upper vocalics, which includes six vowels and
three semivowels, articulated relatively high in the mouth, and lower
vocalics, which includes five vowels and one semivowels, articulated
relatively low. The table below gives further details on this.
The Vocalic System, Thompson (1965, p.12)
It can be made clearer from this table what Thompson (1965) has
illustrated. The upper vocalics includes three positions, being
relatively distinctive from each other: front, back unrounded, and
back rounded. A high vowel, an upper-mid vowel, and a semivowel
occupy each of the positions. He emphasizes that there are no vowels

14. 8
that occur at the final position. Further description of the uper-
vocalics vowels are provided as follows.
/i/ is proposed here as a high front or central unrounded vowel. It is
lower high central before final ch, nh, as in ích, be useful, and lính,
soldier. Before ê, p, m in the same syllable, it is an upper high front
vowel. Examples are provided as in biết, miệng, kíp, tìm, which
means know, mouth, be urgent, and search for respectively. It is
lower high front elsewhere in the same syllable.
/e/ is characterized as being upper mid front or central, unrounded. It
is upper mid central before final ch, nh; and after [i] before [w, p, m,
t, n] in the same syllable, which is “slightly lower before [w]” (p.30).
Examples given include ếch, bênh, hiểu, tiếp, which respectively
means frog, defend, understand, and receive in English. The vowel is
upper-mid front elsewhere.
/u/ is described as a high back rounded vowel. Thomson (1965)
emphasizes that “it tends to be upper high, but only before [m] and
[p]” (p.31), as in chụp (seize suddenly), chum (earthenware jar), and
it will be lower high elsewhere, as in núi, (mountain), mũ, (hat), tuổi,
(age).
/o/ is identified as being upper mid back rounded. It is higher mid
before [j, w], as in tôi, (I), rồi, (be already accomplished), cô, (aunt),
lỗ, (hole), and is mid strongly centralized after [u], as in buồn, (be

15. 9
sad), quốc, (country), tuổi, (age), chuột, (rat). Finally, it is upper mid
elsewhere, that is, before [p, m, t, n].
/ε/ is proposed to be lower mid front unrounded. There is little
variation when the sound is realized in different contexts.
/ɔ/, is much like that of /ε/, maintaining its quality when being
distributed differently. The vowel is described as lower mid back
rounded.
/a/ is characterized as a lower low front unrounded vowel.
Đoàn (2000) has proposed the largest vowel inventory of
Vietnamese, with thirteen monophthongs, including /i/, /e/, /ɛ/, /ɛ̆/,
/ɯ/, /u/, /o, /ɔ/, /ɔ̆/, /ɤ/, /ɤ̆/, /a/, and /ă/. The author did not attempt to
describe these vowels in terms of how they are articulated, as
articulatory phoneticians have often done. Instead, qualities of all the
vowels are described firstly in terms of their timbre. The timbre is
then explained as being high (bổng), mid-low (trầm vừa), and low
(trầm). The table below illustrates how Vietnamese monophthongs
are distinguished from each other in terms of their timbre, according
to the author. (p.191)
- High category: /i, e, ɛ, ɛ̆/
- Mid-low category: /ɯ, ɤ, ɤ̆, a, ă/
- Low category: /u, o, ɔ, ɔ̆/

16. 10
However, it is not clear from the explanation what the vowels are
high, mid-low, and low in terms of. If that is concerned with pitch,
there appears to be confusion between the vowel quality and the
pitch at which they are produced. Acoustic studies of vowels have
demonstrated that the pitch of vowels, as perceived by listeners, is
decided by the fundamental frequencies of the sound waves
producing that vowel (F0), and has practically no effect on the vowel
quality.
There are four pairs of Vietnamese vowels, which according to the
study, differentiated by duration. These include /ɛ̆/ and /ɛ/, /ɔ̆/ and
/ɔ/, / / and /ă/, /ɤ/ and /ɤ̆/. It is maintained that these four
pairs of vowel have the same quality, and are in long-short
opposition. (p.195)
2.2 The acoustic description attempts
Matt et al. (2009) carried out an exploration of the Vietnamese
monophthongs produced by a small group of native speakers from
both northern and southern Vietnam. The researchers also attempted
to provide a comparison between the native production and those
made by American adult learners. The goals of the study are
significant. The method of conducting the study, however, is
problematic. In order to eliminate the anatomical differences among
participants, the normalization method inspired by Watt and

17. 11
Fabricious (1973) has been employed in the study. This method has
been severely attacked by modern phoneticians.
Johnson (2005) pointed out that, “Talkers may differ from each other
at the level of their articulatory habits of speech. This, in itself,
would suggest that perception may not be able to depend on vocal
tract normalization to “remove” talker differences by removing vocal
tract differences” (p.19). Johnson et al. (1993) goes further:
The presence of individual differences in speech production also
complicates matters for vocal tract normalization. Though normalization
research has usually focused on male/female differences in vocal tract size
and shape, vocal tracts - even within genders - come in lots of different
sizes and shapes. Talkers apparently adopt different (possibly arbitrarily
different) articulatory strategies to produce the “same” sounds. Thus,
accurate recovery of the talker’s articulatory gestures would not
completely succeed in “normalizing” speech. (P.20)
The second problem of the method is in its scale. The study was
conducted on too small a scale so as to provide a conclusive support
for the researchers’ claims in the discussion of the findings.
According to the researchers,
Native speaker participants included 3 Northern dialect speakers (1 female,
2 males) and 1 Southern dialect speaker (female). All were originally from
Vietnam and had been living in an English-speaking country for 6 to 26
years. They ranged from 42 to 64, and all had experience teaching
Vietnamese as a foreign language to adults.

18. 12
Firstly, the number of participants selected is too small, and is
therefore statistically insignificant. This can be attributed to the
authors’ reliance on the normalization method adopted, as mentioned
before. Secondly, while the qualities of Vietnamese vowels have
been recognized as being substantially varied from dialect to dialect
in realization, there is no indication that the subjects were screened
for dialect, and very little information is provided about the dialects
of the speakers. The present research represents the researcher’s
attempt to address these limitations. (see Chapter 3 for further
details)
Srihari and Nguyen (2004) is another attempt to describe the
Vietnamese vowel characteristics employing spectrograms analysis.
In order to make decision on the set of vowels for the recording
process, the authors follow the work of Thompson (1965, 1987),
closely, claiming that there are eleven monophthongs in the
Vietnamese vowel system (Hanoi dialect), which are /i, ɯ, u, e, γ, o,
ε, ɔ, ɐ, a, ɑ

19. 13
The vocalics systems (Thompson, 1987, as cited in Srihari and Nguyen, 2004)
Making a comparison with the system that Mai, Vu, and
Hoang (2008) proposed, considerable differences could be
spotted. In the latter account, it is suggested that there are 13
pure vowels in the system, and noticeably, there is not an
existence of /ɑ/, characterized as a low, back, unrounded
vowel, as Srihari and Nguyen (2004) maintain. In addition,
these authors support the claim that /γ, o, ε/ have three
counterparts differing just in terms of duration, which are /ɤ̆/, /ɔ̆/,
and /ɛ̆/. This is a part of the inconsistent description of the
Vietnamese vowel inventory, as mentioned earlier. Even Thompson
(1987) has departed from his previous proposal made in Thompson
(1965), with regards to the existence of /ɑ/. As a result, deciding on
a set of eleven monophthongs has posed a threat to the validity of the
findings.
The aims of the study, as stated by its author, are to provide “a
preliminary quantitative description of formant values for F1 and F2
for each vowel and plot the vowel chart of Vietnamese.” (p.2).
However, what has made it even more problematic, again, is the
scale of the research. The subject of the study, as described, is “a 24-
year-old native male speaker of Hanoi dialect, the standard dialect of
Vietnam. The speaker can speak English fluently but not well-trained
in phonetics.” (p.2). This problem also occurred in the previous

20. 14
study. There are anatomical differences among speakers of a certain
language; therefore, selecting one subject for examination would not
provide findings which are representative of the population. Given
that the author would carry out an analysis on the qualitative aspects
of the vowels in question, the conclusion on the acoustics of the
vowels of a language being drawn from the analysis of the recording
of a single speaker of it is seriously questionable. Ladefoged (2003)
pointed out that, “The fact that data has been measured correctly does
not show that there are no problems with the speakers. When looking
at the formants of a group of people you should check whether any
one speaker is different in any way from the others.” (p.129)
The vowels of five speakers of Banawa, Ladefoged (2003, p.129)

21. 15
The ellipse in the figure encloses four stressed [e] vowels of a
speaker. As can be seen, the first formant values of his [e] are
distinct from those of the other speakers. This speaker, therefore, has
produced this sound in a way that is significantly different from the
others. This deviation, according to Ladefoged (2003), cannot be
ascribed to some anatomical factor such as a very small vocal tract
size. This is because the other vowels produced by him are similar to
those made by the rest of the speakers. The author’s suggestion is
that, “if you find a speaker who pronounces a word in a significantly
different way, you should leave this part of the data out when
providing diagrams of the vowel qualities of the language, noting,
however, that there are speakers who deviate from the general
pattern.” (p.129).
The second problem with the currently reviewed study involves the
set of words containing the vowels chosen for recording.
The word list containing the vowels in question, Srihari and Nguyen (2004, p.3)

22. 16
The /t-/ context is not the best choice. According to Ladefoged
(2011, p.199), a stop closure will cause the vowel’s first formant
(F1) to rise from a low position. As a result, the accuracy of the
formant values calculated might be affected. It is suggested in a
number of the studies (James et al., 1995; Broadbent & Ladefoged,
1957; Wells, 1962; Ladefoged, 2011) that a word list of the /h-d/
context would provide the best spectrograms, as /h/ has almost no
effect on the formants of the adjacent vowels in the same syllable.
2.3. Characterizing vowel qualities with the acoustic properties
The current study is inspired by Ladefoged’s (2003) firm statement
that, “the best way of describing vowels is not in terms of the
articulations involved, but in terms of their acoustic properties.”
(p.104). In this section we shall take a closer look at the acoustics of
vowels.
The different sounds of language are physically characterized with
four dimensions, which are the fundamental frequency, the
amplitude, the duration, and the formants distribution of the sound
wave. The four corresponding perceptual dimensions are pitch,
loudness, length, and quality.
The current study has not investigated the amplitude and the
fundamental frequency of vowels, being primarily concerned with
the spectral distribution of the pure vowels. The measurements of the
vowel duration have been investigated insofar as they distinguish the

23. 17
pairs of vowels having been described with inconsistency in
articulatory phonetics.
Articulatory phonetics describes how a vowel is articulated, in terms
of the behaviors of the articulators, but there has not been a term to
describe the difference between the quality or timber of one vowel
and another vowel. Among the dimensions of the complex sound
waves produced by the human vocal cords, we need to consider
carefully the spectral distribution of the component frequency. A
speaker can pronounce a vowel on any pitch within the range of his
voice without changing its identity. Ladefoged (2003) provides a
prime example:
I can say the vowels in heed, hid, head, had on a low pitch, when the vocal
folds are vibrating about 80 times a second, and then I can say them again with
vocal folds vibrating 160 times a second. The pitch of my voice will have
changed, but the vowels will still have the same quality. I can also say any
vowel loudly or softly. The quality, the factor that distinguishes one vowel from
another, remains the same when I shout or talk quietly. (p.31)
The differences among vowels are often compared with the different
instruments. The same note can be played on a guitar, a violin, or a
piano. This can be done as the sound is produced at the same rate of
repetition of a special component wave, i.e, the fundamental
frequency. What is interesting here is that, the quality of the music
produced by one instrument will be different from that of any other.
This is due to the differences in the amplitude as well as the
frequency of the component waves. The quality of a vowel differs

24. 18
from that of another in plainly the same way. Irrespective of the
pitch on which a vowel is produced, the quality will stay unchanged.
A popular way that phoneticians describe the acoustics of the human
speech sounds is using the tube models. The current research is
primarily concerned with the monophthongs (of Vietnamese), so the
models can be conveniently summarized as follows.
The air in a bottle will be set vibrating when the body of air at the
top of it is blown across. Naturally, the note that is produced as a
result of blowing the air at the bottle top will depend on the size and
the shape of the bottle. The more the volume of air inside is
increased, the lower will the produced note be. This is due to the fact
that the smaller body of air will vibrate more quickly than that of a
larger one, having a higher frequency of resonance.
When a vowel is being produced, it is the vocal tract that acts like a
bottle, with the size and the shape being constantly altered. If for a
bottle, the air inside is set in vibration when blowing across the air at
the top, for the vocal tract it is the pulses of the air from the vocal
folds. What makes the tract different from the bottle is its very
complex shape, which can be constantly changed due to the
movements of the related organs. Conveniently, phoneticians often
consider the body of air in the throat to be the first tube, and that in
the mouth to be the second one. The resonances of the vocal tract are
called the formants, which correspond to the basic frequencies of the
vibrations of the air in the vocal tract. Therefore, the formants of a

25. 19
sound are the properties that directly depend on the size and the
shape of the tract, both the front and the back part of the cavity. They
are largely responsible for the characteristic quality of the vowel. My
vowel [i] in the Vietnamese word hi is characterized by formants
around 380, 2200, and 3200 Hz.
Figure 1: The spectrogram of the author’s pronunciation of [i] in hi
When my vowel [i] is produced, a damped wave is generated, and
always with these approximate basic frequencies. It is this set of
components that allow us to distinguish [i] from the other vowels.
Each vowel is associated with a different shape of the vocal tract,
resulting in the different component basic frequencies (the formants)
being produced when the body of air inside vibrates.

26. 20
The traditional articulatory descriptions of vowels show a close
relationship with the frequencies of the formants of the vowels. As
the acoustic studies of vowels have demonstrated, the frequency of
the first formant (F1) is responsible for the vowel quality of being
high or low, and that of the second formant effects the degree of
frontness or backness, as described in articulatory phonetics. This
can be more clearly illustrated with a formant chart of English
vowels taken from Johnson (2011), as follows.
A formant chart showing the frequency of the first formant on the ordinate
plotted against the second formant on the abscissa, by Johnson (2011, p.197)

27. 21
As it can be seen from the chart, in comparison with the first formant
frequency of [i], the first formant of the vowel [a] increases
noticeably. It is also apparent that, in these vowels, as the height of
the vowels decreases, their F1 increase. As for the second formant
frequencies, it is markedly higher for the front vowels than in the
back vowels. Briefly, in relation to the descriptions in articulatory
phonetics, the degree of frontness or backness varies proportionally
with the frequency of the second formant (F2), and the height of the
vowels varies inversely with the first formant frequency (F1).
In the previous reviews of the two studies on the vowels of
Vietnamese, I have questioned the conclusion of the authors, because
of the scale on which the research was conducted, ranging from one
to four native speakers as the subjects. It is now that this can be
further justified. As Ladefoged (2001) has pointed out, we can
describe the vowel qualities of a particular vowel, produced by a
particular speaker by calculating the value of the first and the second
formant. However, due to the anatomical differences among
speakers, the precise formant frequencies that the vocal folds’
vibrations generate might be comparatively different. For instance, a
speaker with a bigger head will have a larger resonating cavity,
which results in his comparatively lower formants, both the F1, and
F2. In contrast, a vowel produced by a speaker with a smaller vocal
tract will have formants with relatively lower formant frequencies.
Ladefoged (2001), concludes that, “In order to represent the vowels
of a language, we need to show the average values of the formants”

28. 22
and “the most useful representation of the vowels of a language is a
plot showing the average values of formant one and formant two for
each vowel as spoken by a group of speakers.” (p.39)
In order to arrange the Vienamese monophthongs investigated in this
study later so as to reflect both the acoustic dimentions as well as the
tongue position as articulatory phoneticians wish, it is essential to
take a closer look at a plotting approach, which has been widely
employed in recent studies.
The answer to this plotting question is in the arrangement of the
frequency scales. Let us take the descriptions of the two vowels /i:/
and /u:/ in consideration, from the articulatory phonetics’
perspectives. When producing /i:/, as in the English word heed, the
speaker’s tongue is pulled up and forward from the rest position so
that it is front and high in the mouth. When producing /u:/, as in
Who’d, however, the position of the tongue is still high, roughly as
high as that of /i:/, but now it is pulled backward.
These facts have a close relation to the formant frequency. While the
tongue position for /i:/ is high, the frequency of the first formant, F1,
is low. It is a front vowel, and its second formant frequency is high.
For that of /u:/, the tongue position is still high. Correspondingly, the
first formant, F1, is high. However, what makes it different from /i:/
is the second formant. As a back vowel, the second formant of /u:/,
F2, is noticeably higher than that of /i:/. As a result, the values of
the first formants of vowels indicate the tongue’s behaviors.

29. 23
Consequently, in order to plot the vowels on a chart to indicate the
formant frequencies as well as the approximation of the tongue
position, the scale of F1 must represent the decreasing values. For
the second formant, as the traditional phonetic diagram shows the
front vowels on the left, and the back vowels on the right, the scale
indicating F2 values must go from right to left, in order to represent
the quality of being front or back. Below is a diagram, with the
scales arranged as discussed aforementioned.
A combined acoustic and articulatory representation of some of the vowels of
American English., Johnson & Ladefoged (2011, p.218)

30. 24
2.4 General American English
2.4.1 The traditional description
One of the ultimate goals of the current study is to compare the
distribution on the formant chart between Hanoi Vietnamese
monophthongs and General American English monophthongs; this
section is devoted for an examination of the concept of General
American English (GA) and its monophthongs in literature.
Generally, phoneticians are united surrounding the definition. The
pronunciation of American English is traditionally divided into the
Eastern pronunciation, which includes New York City and New
England, Southern, which stretches from Virginia to Texas and the
southwards, and General, which includes all the remaining. General
American, GA, is comparable with RP in Britain. A speaker of GA is
a person whose accent does not tell which region of the country he
comes from. Put it another way, GA is described as having no
characteristics of a specific region in the United States. Just as RP,
sometimes referred to as Queen’s English, or BBC English, GA is
often referred to as Network English. “It is the standard model for the
pronunciation of English as an L2 in parts of Asia, and parts of Latin
America.” (Gimson, 2008, p.84)
According to Wells (1982), there are two major systemic differences
between British RP and GA. Firstly, in RP, there are three
diphthongs /iə/, /eə/, /ʊə/ which cannot be found in GA. Instead, in

31. 25
GA, there are sequences of short vowel plus /r/, such as in heard,
fare /bɪrd/, /fer/. Secondly, there is no /ɒ/ in GA. In RP hot is
pronounced as /hɒt/, but in GA, it will become /hɑ:t/. This is true
with virtually all the other cases of /ɒ/ in RP, such as in bottle, cot,
pot, spot. However, Gimson (2008) also points out that a limited
subset of GA has /ɔ:/, for example, across, gone, often, cough,
orange, porridge.
In terms of the lexical occurrence, the differences are in words of RP
having /ɑ:/, while in GA, they become /æ/. Gimson (2008) also
stresses that this commonly happens in the context before a voiceless
fricative, or before a nasal followed by another consonant. For
example, RP past [pɑ:st] is GA [pæst].
Bellow is the further examples of the comparison between RP and
GA vowels, provided by Gomez (2012, p.12).

32. 26
Change of vowel /ɒ/ to /ɑ:/. and /ɔ:/,
Regarding the diphthongs, which is not the primary concern of the
current study, the differences between the two systems are varied.
The most noticeable change is the shift from /əʊ/ in RP to that of /oʊ/
in GA, such as in home, [həʊm] of RP, and [hoʊm] GA. As Gomez
(2012) has pointed out, the shift is concerned with the change of the
mid central unrounded vowel /ə/ to the close-mid back rounded

33. 27
vowel /o/ in the first vowel of the diphthong. This shift, according to
the author, is considered to be systematic. He offers several
examples of this change in the table below. (p.14)
2.4.2 The acoustics of GA
Hillenbrand et al. (1995) conducted a study of the acoustic properties
of GA. The vowels /ɪ, i, e, ɜ, æ, a, ɔ, o, ʊ, u, ʌ, ɝ/ in /h-v-d/
syllables, produced by 45 men, 48 women, and 46 children were
recorded.
The majority of the participants, (87%), were born and raised in
Michigan’s Lower Peninsula, the southeastern and southwestern
parts of the state of Michigan. The remaining were from other parts
of upper Midwest, including Illinois, Wisconsin, Minnesota, northern
Ohio, and northern Indiana. In order to increase the homogeneity of
the sample, ensuring that they all speak GA, a procedure of selecting
the subjects from the larger group, described by the researchers as
being “an extensive screening procedure” was conducted. The key

34. 28
part of the procedure was a careful assessment of dialect. It focused
on the subjects’ production of /a/ - /ɔ/ distinction.
The formants of F1-F4 were measured from the LPC spectra. Below
are the average F1-F2 formant charts of pure vowels as produced by
American men and women.
The average formant frequencies of the pure vowels produced by
American men (Hillenbrand et al., 1995, p.1304)

35. 29
The average formant frequencies of pure vowels produced by American
women (Hillenbrand et al., 1995, p.1304)
It is clear from the charts that, although the absolute values of the
formant frequencies between men and women are significantly
different, due to the anatomical differences between two sexes, the
relative positions of the monophthongs on the charts, indicating how
these vowels are articulated, are strikingly similar.

36. 30
Chapter 3 RESEARCH METHODOLOGY
3.1 The subjects
Ten female speakers of Hanoi Vietnamese were chosen in a
procedure as follows. First, 20 females aged from 15 to 25, who
claimed to have spent most of their life, since being born, in Hanoi
were chosen to take part in a recording process. They were then
asked to read a short piece of Vietnamese scripts (Appendix 2). After
that each of the recordings was played back to all the subjects,
except for the person producing it. The listeners were asked to judge
whether each piece of speech sounds typically Hanoi Vietnamese,
giving a score ranging from one to ten, with ten being most typical,
and one being the least. Ten of the twenty subjects who achieved the
highest scores were selected. This procedure ensured the high
homogeneity among the subjects.
3.2 The stimuli
Thirteen Vietnamese monophthongs were investigated. In different
accounts proposed by different authors, as discussed in the review of
literature, the number of monophthongs in the system is a matter of
controversy. Whether the pairs of vowels, as in anh (brother) and xe
(vehicle), ong (bee) and oong, ha and hay (interesting), hơ and hân
should be described as two vowels in long-short opposition, having
the same vowel qualities, represented by /ɛ̆/ and /ɛ/ /ɔ̃/ and /ɔ/ ,
/ / and /ă/, /ɤ/ and /ɤ̆/ respectively, or they are vowels with

37. 31
distinct quality, or /ɛ̆/, /ɔ̃/, /ă/, and /ɤ̆/ are allophones of the longer
counterparts, have divided linguists. The current research treated
them as being distinct from each other, either in terms of the
qualities or duration; therefore, the quality of these thirteen vowels,
which is the largest inventory proposed so far, were investigated.
Based on the results of the acoustic analysis of F1 and F2, the
controversial matters would be discussed in the section of findings
and discussion. To record the subjects’ production of these vowels,
/i, e, ɛ, ɛ̆, ɯ, u, o, ɔ, ɔ̆, ɤ, ɤ̆, a, ă/ were divided into two sets. The first
set, including /i, e, ɛ, ɯ, u, o, ɔ, ɤ, a,/ are represented by the
corresponding letters in the Vietnamese alphabet, i, ê, e, ư, u, ô, o, ơ,
a. The second set, including, /ɛ̆/, /ɔ̆/, /ɤ̆/, and /ă/, as described by
linguists, have limited distribution. Therefore, they are realized in
four words, anh, óc, ân, ay respectively.
3.3 The recording process
The subjects were required to say the given words and letters two
times to the Shure PG27USB microphone, with the relevant
specifications information provided by the producer as follows:
 Frequency Response: 20 to 20,000 Hz
 Power Requirements: USB-powered, 500 mA maximum
 Sampling Rate: up to 48 kHz
The USB Plug and Play microphone was chosen instead of the
traditional plug as suggested by Jonhson (personal communication,

38. 32
December 19, 2011). This connectivity method allowed the
researcher to conduct convenient digital recording anywhere that a
computer can be taken along. In addition, the integrated pre-amp
with Microphone Gain Control allows the control of input signal
strength, meaning there is no requirement of an amplifier. This is
especially suitable for phonetic fieldwork, where it is commonly
impossible to take the speakers of a speech community to a
laboratory for recording.
The microphone was set up with a personal computer with the
specifications as follows:
 Processor: Intel Core i5 2.5 GHz
 Motherboard chipset: Intel 965GM
 Ports 4 x USB 2.0; FireWire; VGA port; S-video port
 Graphics hardware: Intel GMA X3100
 Screen resolution: (max) 1,280 x 800
 Hard drive: 500 GB
The subjects’ productions of the sounds were recorded at a sampling
rate of 11025 Hz, in a 20m2 quiet room.
The data were stored on the computer. Different copies were made
and stored in case of hard disk errors.
3.4 The analysis process

39. 33
F1 and F2 of each vowel were measured. The mean of F1 and F2 of
each vowels were then plotted on a diagram with JPlotFormants
v1.4, a freeware program developed by Roger Billerey (2011), at the
University of California, Los Angeles, which “lets you enter and plot
formant pairs (F1, F2) for an unlimited number of vowels.” (Billerey,
2011). It runs on a Java-enabled platform, in the case of the current
research, Microsoft Windows. The parameters of the plot can be
easily customized, in terms of the size, the colors and the symbols.
The formant values and an acoustic vowel chart of the Hanoi
Vietnamese monophthongs were then compared with the values
found for General American English monophthongs, by Clark et al.
(1995).

40. 34
Chapter 4: FINDINGS AND DISCUSSION
4.1 The acoustics of Hanoi Vietnamese monophthongs
Table 1 presents the information on the values of F1 and F2 of all the
subjects for each vowel in question. The values are the average
values of the two tokens. The first column on the left contains the
labeled subjects.
[i] [e] [ɛ] [ɛ̆] [ɯ] [u] [o] [ɔ] [ɤ] [ɤ̆] [a] [ă]
S1
F1 370 590 680 1109 346 370 572 885 733 825 1164 1205
F2 2801 2430 2600 1720 1326 795 969 1153 1369 1413 1801 1713
S2
F1 354 538 646 1085 401 413 496 906 786 852 1131 1179
F2 2795 2462 2558 1852 1295 701 944 1201 1312 1290 1806 1796
S3
F1 395 506 607 1172 357 341 507 892 725 821 1017 1124
F2 2817 2399 2501 1709 1331 772 1002 1213 1397 1435 1828 1801
S4
F1 397 530 651 1123 426 386 516 911 814 811 1123 1122
F2 2929 2410 2672 1806 1301 817 1112 1199 1306 1303 1901 1812
S5
F1 417 605 726 1186 480 486 604 1002 729 785 1103 1144
F2 2902 2601 2712 1995 1310 812 977 1294 1331 1397 1974 1920
S6
F1 298 511 701 1002 482 365 510 772 755 748 1177 1165
F2 2776 2312 2503 1706 1246 921 944 1188 1227 1358 1721 1704
S7
F1 355 563 670 975 397 401 575 823 684 703 1021 1190
F2 2738 2307 2598 1751 1393 832 891 1186 1317 1341 1754 1801
S8
F1 343 542 729 1186 411 393 509 922 670 584 1133 1134
F2 3071 2506 2650 1794 1304 912 1018 1212 1291 1321 1808 1782
S9
F1 311 612 742 1034 402 367 612 814 705 692 1110 1121
F2 3012 2615 2621 1743 1326 824 1011 1203 1249 1344 1788 1877
S10
F1 312 566 755 1237 459 512 653 877 683 731 1193 1225
F2 2865 2431 2344 1865 1328 879 1104 1197 1222 1314 1881 1814

41. 35
Table 1: The first and second formant frequencies of all the subjects for each
monophthong. The values are the average values of the two tokens.
4.1.1 [ɛ̆] and [ɛ]
The measurement the formants of [ɛ̆] as in anh, [ɛ̆ɲ] posed
potential problems. [ɲ] is a nasal consonant. As a result, its
formants would have an influence on the formants of the vowel
preceding it. The influence is explained below. The effect would
be the same if the consonant had been replaced by /k/ as in
ách. Therefore, if [ɛ̆] is a monophthong as described in
literature, the formant contours would be affected.
Unfortunately, these are the only two possibilities of the
distribution of this vowel. Before examining the impact it has
on [ɛ̆] in the words produced by the subjects, let us consider
the extent to which [ɲ] affects the vowels in syllables to which
it belongs. The figures below represent the spectrograms
illustrating the effect of [ɲ] on [i] in inh and nhi.

42. 36
Figure 2: The effect of [ɲ]on [i] in inh and nhi, as produced by the researcher.
The spectrogram of inh is on the left, and that of nhi is on the right.
It appears that there is practically no effect on the vowel in both
cases. The contours of both F1 and F2 remain steady throughout the
time duration of the vowels.
There is, however, a less black segment on both spectrograms, at the
starting in nhi, and at the ending in inh. This is highlighted in the
figure. Interestingly, these segments contain two dark bands at the
same frequency range of F1 and F2 of the following vowel [i]. This
suggests that the two bands of dark color might be the properties of
[ɲ] being the two formants of the consonant. If the formants of [ɲ]
have roughly the same values as that of [i], the effect that [ɲ]
produces on [i] would not be obvious. The situation would be
different if the following vowels have considerably different F1 and
F2 from those of [i], such as [a]. The following figure presents the
spectrogram of the researcher’s pronunciation of nha.

43. 37
Figure 3: The effect of [ɲ] on [a] in nha
As obviously shown in the spectrogram, [ɲ] has markedly increased
the second formant of [a] at the starting of the formant contour. In
contrast, the first formant of the vowel has substantially decreased at
the same point. F1 and F2 increases and decreases respectively and
reach the normal values only at the end of the formant contours. It
can be concluded from the examination of the spectrograms of inh,
nhi, and nha that [ɲ] has two formants of approximately the same
values as that of [i]. The consonant’s formants, therefore, has
definitely affected the formant frequencies of the vowel [ɛ̆] in anh,
[ɛ̆ɲ]. The segment that best reflects F1 and F2 of [ɛ̆], as a result,
is at the starting of the formant contours. These are the values
represented in table 1.

44. 38
It is clearly seen from the table that while [ɛ] has F1 at below 1000
Hz, ranging from 607 Hz to 755 Hz, and F2 above 2000 Hz, ranging
from 2344 Hz to 2712 Hz, being characteristic of an open-mid front
vowel as described in traditional phonetics, the formant frequencies
of [ɛ̆] has a strikingly similar values to those of [a]. Both [a] and [ɛ̆]
have the first two formant frequencies at around 1100 Hz and
1800 Hz, being typical of an open near front vowel. The figures
below illustrate the differences between [ɛ̆] and [ɛ] and the
similarities between [ɛ̆] and [a] in terms of the vowel qualities.
Figure 4: The difference between the vowel in e and anh, produced by a
subject. The spectrogram of e is on the left, and of anh is on the right.

45. 39
Figure 5: The difference between the vowel in e and anh, produced by
another subject. The spectrogram of e is on the left, and of anh is on the
right.

46. 40
Figure 6: The similarities between the vowel in anh and ay, produced by
a subject. The spectrogram of anh is on the left, and of ay is on the right.
Figure 7: The similarities between the vowel in anh and ay, produced by
another subject. The spectrogram of anh is on the left, and of ay is on
the right.
It is suggested from the findings that /ɛ̆/ and /ɛ/ are two vowels with
distinct qualities, and that /ɛ̆/, as investigated in the current research
and /a/ are two vowels with the same quality, being distinct from
each other only by the duration. It would be, therefore, more
appropriate for the current /ɛ̆/ to be represented by the IPA symbol
/ă/.
4.1.2 [ɤ] and [ɤ̆]

47. 41
The situation with [ɤ] and [ɤ̆] is different. As shown from the table
the values of the first and the second formants of these vowels are
much similar to each other. The mean of F1 for [ɤ] is 728 Hz, while
that of [ɤ̆] is 752 Hz. The second formant of [ɤ] varies from 1222 Hz
to 1369 Hz, which bears similarity to that of [ɤ̆] (1314 Hz-1435 Hz).
These formant values are characteristic of an open-mid central vowel
described in traditional phonetics. Although both formant
frequencies of [ɤ̆] are slightly higher than those of [ɤ], indicating
that the former is to some extent farther to the left and lower than the
latter vowel on the formant chart (the vowel chart), the degree of
similarity is significant. The data, therefore, have not fully confirmed
the claim of Đoàn (2000, p.195) that /ɤ/ and /ɤ̆/ are two vowels of
the same quality. However, that [ɤ]and [ɤ̆] are very close in terms of
vowel qualities must be acknowledged. The finding of this study also
strongly supports his firm statement that “the vowel in sân [sɤ̆n] is
always shorter than the vowel in sơn [sɤn]. The role of duration is
fundamental.” (p.196). A closer examination of the vowel duration
from the spectrogram (see below) illustrates how [ɤ]is distinguished
from [ɤ̆] by the difference in duration.

48. 42
Figure 8: Spectrograms of [ɤ]and [ɤ̆n]
The spectrogram on the left shows virtually the same frequencies of
F1 and F2 of [ɤ] as those of [ɤ̆], which is on the left. While the
formant contours of the former vowel stays constant from the starting
to the ending, F2 of [ɤ̆] goes up slightly. This is an indication of the
impact of the following consonant [n]. It is also obvious from the
figure that the duration of [ɤ̆] is considerably longer than that of [ɤ̆].
It is very unlikely that [ɤ̆] is shorter as a result of the following
consonant [n]. Let us examine the contrast in the minimal pair of
vowels in ơn and ân. The environment is the same, regarding the
following consonant [n]. It is the difference in the duration of the
vowel in ơn [ɤn], and ân [ɤ̆n] that distinguishes the words from each

49. 43
other. The following figure shows the spectrograms of the
researcher’s pronunciation of [ɤn] and [ɤ̆n].
Figure 9: Spectrograms of [ɤn], on the left, and [ɤ̆n], on the right
The formant frequencies are approximately the same at the starting
and the ending of both words. The only apparent difference is the
duration. It is clear from this figure that /ɤ/ and /ɤ̆/ are two different
vowels. The qualities are similar, but it is the duration that makes
them two distinct vowels.
4.1.3 [a] and [ă]

50. 44
Let us now turn to another pair of vowels of controversy. /a/ and /ă/
have been characterized as two vowels of the same quality, differing
from each other fundamentally in terms of duration. They are
therefore, treated as two distinct vowel, and it is the duration that
makes them two distinct sounds. It is also admitted that there are
other authors who have accounted for these vowels’ qualities
differently. While /a/ has been described as an open central
unrounded vowel, /ă/ is characterized as being mid, unrounded,
central, but farther to the front.
The measurement of the vowels’ first and second formant frequency,
as indicated from Table 1 has demonstrated that they are of the same
quality. While [a] receives the mean of its F1 at 1117 Hz, and 1826
Hz for F2, the corresponding formants of [ă] measure 1163 Hz and
1802 Hz respectively. The differences are statistically insignificant,
and the differences in terms of vowel qualities are trivial. The
following figures illustrate the virtually identical values of the
vowels’ first and second formants.
Because the vowels under investigation are not in the same
environment in this pair of words (To put it simple, they are not a
minimal pair), the spectrogram below shall not be employed to
examine the vowels’ distinction in terms of duration. Instead, we are
primarily concerned with the vowels’ quality.

51. 45
Figure 10: The similarities between the vowel in a [a] and ay [ăi],
produced by a subject. The spectrogram of [a] is on the left, and of [ăi] is
on the right.
It is not the central focus of the current research to go for or against
the approaches toward describing the syllable structure of
Vietnamese. Nevertheless, it is arguable from the figure that the
formants contours of [ăi] behave characteristically like a diphthong.
For approximately one third of the contours of [ăi], which is
represented in the spectrogram on the right, the formant frequencies
stay fairly constant, at roughly 1100 Hz for F1, and 1700 Hz for F2,
which are virtually the same as those of the vowel on the left. This is
the section where [ăi] sounds [ă]. The first formant then decreases
considerably before reaching a steady state, at roughly 350 Hz, while

52. 46
F2 goes up to approximately 2700 Hz at the steady segment of the
contour. These frequency values are characteristic of the vowel [i].
In order to demonstrate the role of duration in distinguishing
between [a] and [ă], let us examine the spectrograms of the minimal
pair: [ai], ai, and [ăi], ay, as shown in figure 11. These sounds are
undeniably perceived as the pronunciation of two different words by
any speaker of the language with normal auditory perception ability.
As a result, there are three possibilities, according to which they
differ, either the quality or the duration of the sounds, or both.
Figure 11: The duration of [a] and [ă] in ai, on the left, and ay, on the
right
It can be observed from the figure that the two spectrograms have
almost similar shape. The formant contours start with the

53. 47
characteristic of an [a] and then glide to that of [i] at the end in both
words. The differences are in that the duration for [a] is considerably
longer in the first spectrogram than in the second. It can be
concluded, therefore, that the duration has distinguished the pair of
words from each other.

54. 48
4.1.4 Regression analysis
Table 2: The values of the first and the second token of each sound produced
by each speaker.
[i] [e] [ɛ] [ɛ̆] [ɯ] [u] [o] [ɔ] [ɤ] [ɤ̆] [a] [ă]
S1
F1- Token 1
F1- Token 2
354
386
556
624
700
661
1100
1119
313
380
402
339
589
554
866
905
754
713
814
836
1206
1122
1200
1211
F2- Token 1
F2- Token 2
2846
2756
2417
2443
2569
2631
1684
1756
1337
1315
780
811
937
1001
1156
1150
1388
1350
1426
1400
1997
1805
1670
1757
S2
F1- Token 1
F1- Token 2
404
304
543
534
640
652
1098
1071
363
439
373
453
526
466
906
907
770
802
830
874
1101
1162
1159
1199
F2- Token 1
F2- Token 2
2810
2780
2495
2429
2528
2591
1844
1860
1301
1289
711
690
903
985
1220
1192
1322
1301
1327
1253
1812
1801
1751
1842
S3
F1- Token 1
F1- Token 2
446
344
490
522
597
618
1138
1207
331
384
355
327
495
519
904
881
690
760
810
832
995
1040
1129
1120
F2- Token 1
F2- Token 2
2850
2784
2450
2350
2523
2480
1714
1705
1293
1370
781
764
1000
1105
1191
1236
1394
1400
1401
1470
1866
1790
1816
1786
S4
F1- Token 1
F1- Token 2
420
374
514
546
674
628
1092
1154
401
452
370
402
526
506
922
901
836
792
792
823
1127
1120
1102
1143
F2- Token 1
F2- Token 2
2915
2943
2400
2422
2656
2688
1819
1794
1313
1290
801
834
1105
1120
1181
1218
1290
1322
1290
1316
1890
1913
1844
1790
S5
F1- Token 1
F1- Token 2
466
367
618
592
695
757
1154
1218
497
464
470
503
639
570
990
1014
701
758
802
768
1093
1114
1103
1185
F2- Token 1
F2- Token 2
2870
2936
2638
2565
2711
2714
1996
1993
1337
1283
773
852
931
1024
1308
1281
1301
1362
1380
1414
1924
2025
1922
1918
S6
F1- Token 1
F1- Token 2
306
290
527
486
681
721
1009
995
486
479
360
371
490
530
780
764
743
767
730
767
1174
1180
1138
1192
F2- Token 1
F2- Token 2
2770
2782
2300
2324
2526
2481
1690
1723
1230
1262
910
933
940
949
1180
1196
1204
1250
1346
1370
1717
1725
1703
1706
S7
F1- Token 1
F1- Token 2
371
339
576
550
651
689
995
956
401
394
411
391
561
590
811
836
684
685
723
683
1012
1031
1170
1211
F2- Token 1
F2- Token 2
2725
2750
2297
2328
2630
2577
1740
1762
1397
1390
821
844
911
872
1907
1856
1308
1326
1341
1342
1768
1740
1820
1782
S8
F1- Token 1
F1- Token 2
336
340
531
553
2714
2744
1172
1201
410
422
406
381
500
518
934
911
672
688
570
599
1110
1156
1138
1131
F2- Token 1
F2- Token 2
3078
3062
2527
2485
2661
2639
1776
1812
1301
1308
917
908
1000
1023
1191
1234
1271
1311
1300
1342
1792
1826
1785
1779
S9
F1- Token 1
F1- Token 2
330
292
589
635
731
754
1020
1048
422
381
374
361
614
610
829
800
691
720
674
710
1110
1111
1100
1142
F2- Token 1
F2- Token 2
2996
3028
2610
2620
2617
2624
1757
1730
1342
1310
823
825
992
1030
1206
1200
1268
1231
1348
1340
1776
1800
1880
1875
S10
F1- Token 1
F1- Token 2
295
330
593
539
749
762
1214
1261
440
478
521
504
666
640
888
866
689
677
730
733
1205
1181
1221
1230
F2- Token 1
F2- Token 2
2886
2844
2430
2432
2328
2350
1850
1881
1314
1342
877
881
1090
1118
1171
1224
1192
1253
1291
1338
1892
1871
1810
1818

55. 49

56. 50

57. 51
Figure 12: The correlation between the two measurements of each F1 and F2 by
the first 4 subjects. One measurement is in the first token of each of the sounds,
and the other is in the second token of the same sound.
As can be seen from the graphs, the formants in the first token of a
given sound recorded is much the same as those of the second token
of the same sound produced by the same speaker. The correlation
coefficients calculated for four subjects range from 0.98 to 0.99,
demonstrating a strong consistency among the speakers and also in
the measurement.
4.1.5 Charting the formants of Hanoi Vietnamese monophthongs
The fact that the data have been measured correctly does not mean
that there are no problems with the speakers. Figure 13 below
presents the first two formants of all vowels of the speakers plotted
against each other, so as to reflect the place of articulation besides
the formant values. The ellipses enclose the vowels with normal
formant frequencies values. The figure indicates that the vowel
quality of [e] and [o] produced by one speaker seems to have slightly
deviated from the norms. The first subject has pronounced the sound
at a lower F2, but at higher F1, making a more back and low vowel,
as compared to the other speakers’.
The plot of formants has also demonstrated better the quality of
vowels the description of which has generated debate among
academics. These have been discussed aforementioned, and can be
further illuminated here.

58. 52
Let us first take the pair of [ɤ] and [ɤ̆] into consideration, with
additional articulatory description being concerned. These vowels
occupy the areas on the chart which are noticeably overlapped,
indicating practically the same qualities of being high, low, front,
and back. However, there are slight differences. To start with, the
first formant values of [ɤ̆] have relatively greater standard deviation
than that of [ɤ] (81 in comparison with 48.1). This indicates that the
quality of being high or low is less stable for [ɤ̆] in contrast with [ɤ].
For the second formant frequencies, the reserve is true. [ɤ̆] receives
the SD of 48, while that of [ɤ] is as high as 57.3, meaning that the
deviation is less striking. The front and back qualities are, therefore,
more similar and more stable. Despite the differences pointed out, it
must be emphasized that these two vowels have much the same
quality and can be arguably represented by the phonetic symbols
employed so far.
The situation is different for the group of four vowels [a], [ă], [ɛ],
and [ɛ̆]. Firstly 14 shows absolutely no quality similarity between the
vowel symbolized as [ɛ] and [ɛ̆]. While [ɛ] features a typical open-
mid front vowel, [ɛ̆] is characterized as a low central vowel.
Expectedly, the location of [ɛ̆] on the chart shares most of its space
with the other two vowels, [a] and [ă]. As discussed aforementioned,
both [ă] and [ɛ̆] have been demonstrated to have relatively similar
duration, shorter than [a]. With the additional quality similarities

59. 53
highlighted, [ɛ̆] as in anh should not be regarded as being distinctive
from the other. It is in fact, a realization of [ă]. However, the
researcher is still reluctant to come to the conclusion that the quality
of the vowel realized in the word chosen, anh, is purely that of an
[ă]. Judgments based on the ears are rather intuitive. Nevertheless, I
am still tempted to say that there seem to be a glide to a vowel
sounding like [i] after [ă] is produced. The spectrograms, in this case
are regretfully not very helpful. As pointed out above, the formant
frequencies of [ɛ̆] are considerably influenced by the following
consonant. This formant, unfortunately, has its first two formants
almost identical to those of [i]. As a result, analyzing the
spectrogram cannot tell whether F1 and F2, as produced in making
[ɛ̆], are respectively falling and rising to those of the following
consonant or to those of a vowel with the qualities of an [i]. What
makes the situation further complicated is that /ɛ̆/ has been described
to have very limited distribution, occurring only before nh and ch,
which affect the preceding vowel in virtually the same way.
It should be noted in passing that although Jplotformant does its job
excellently in displaying the vowel formant values, offering a range
of very practical plotting options, it has not supported the font with
IPA symbols yet. As a result, the letters and the words containing the
vowels, instead of the phonetic symbols, have been used when the
formant frequency values are plotted on the chart, as it is shown in
the figure.

60. 54
Figure 13: The monophthongs of ten speakers of Vietnamese in Hanoi dialect
The table below presents the average F1 and F2 of all the vowels in
question, followed by the formant chart, which is acknowledged as
“the most useful representation of the vowels of a language”
(Ladefoged, 2001, p.39)
[i] [e] [ɛ] [ɯ] [u] [o] [ɔ] [ɤ] [ɤ̆] [a] [ă]
Mean F1 355 556 690 416 403 555 880 728 755 1117 1135
Mean F2 2870 2447 2575 1446 826 997 1204 1302 1351 1826 1798
Table 3: The average values of F1 and F2 for each monophthong as spoken by
ten speakers

61. 55
Figure 14: The formant chart showing the average values of F1 and F2 for each
monophthong as spoken by ten speakers
In the chart above, the axes and the tick marks have been simplified
and arranged in accordance with Hillenbrand et al. (1995) for the
sake of the vowel quality comparison in the later section of this
thesis.
The vowel [i] occupies a position on the chart which is highest and
farthest to the left, featuring the most front and close vowel of the
inventory. The vowel [e] is slightly lower and further back,
indicating the close-mid front qualities. While [ɛ] is below [e] and is
a short distance further to the left, featuring a relatively open-mid

62. 56
front vowel, it must be emphasized that these two vowels have
considerable degree of similarity. At this point, a drawback of the
plotting program must also be taken into account. The marks on F2
axe are equally spaced, 200 Hz apart, which has been shown not to
reflect how the human sense of hearing really perceives the sounds.
While with the frequency between 300 and 1000 Hz, the perceived
pitch of a note increases linearly, so that the difference in pitch of a
note with frequencies of 300 Hz and 400 Hz is much the same as the
difference between notes with frequencies of 500 Hz and 600 Hz.
However, between 1000 and 10000 Hz, the pitch interval between
two notes depends on the ratio of the frequencies, rather than the
absolute value of the difference between the note with the higher
frequency and the note with lower frequency. For example, there is
an equal interval of pitch between notes from 1200 Hz to 2400 Hz
and notes from 4000 Hz to 8000 Hz, as the ratios between the higher
and the lower note in these two pairs both equal ½.
The figure below illustrates how Ladefoged (2011, p.187) adjusts the
tick mark spacing on F2 axe to reflect what would better reflect the
human perception of audio frequency. As it can be seen, for
frequencies above 1000 Hz, the space between tick marks is
increasingly closer relatively with the increase of the frequencies.

63. 57
Figure 15: A formant chart showing the formant frequency F1 and F2 for eight
English monophthongs. The scales are marked in Hz, arranged at Bark scale
intervals
Taking this into account, [a] and [ă], despite having F2 at the middle
of the axe segment, would in fact be more front than those at the
central of the chart. They are also the most open vowels in the
inventory, with [ă] being very slightly farther down on F1 axe. The
difference in F2, indicating the front and back quality differences, is
insignificant.
In the central area of the chart, there are three vowels, [ɯ], [ɤ], and
[ɤ̆]. While [ɯ] is typically close, with very low F1, the others feature
mid-open vowels, and are a relatively short distance further to the
right. The differences between [ɤ] and [ɤ̆] in terms of F1 and F2, or

64. 58
the front, back, close, open qualities is of little importance in
contrasting one from the other, although the later vowel has higher
F1. It is the duration that must be taken into consideration here, as
Đoàn (ibid., p.197) always insists.
As compared to the previous group, [ɔ] is a more open and more
back vowel, but not as open as [a], and is not far enough to the right
of the chart so as to be considered a typically back vowel.
The two remaining vowels are [u] and [o]. The former is as close as
[ɯ], and is the most back vowel, with [o] is a little more front and
more open.
4.2 The monophthongs of Hanoi Vietnamese and General
American English in comparison

65. 59
Figure 16: The formant chart of Vietnamese monophthongs produced by
female speakers
Figure 17: The formant chart of General American English monophthongs
produced by female speakers
Before the comparison can be drawn, it must be highlighted that due
to the anatomical differences between Vietnamese females and
American females, a comparison and contrast of the absolute value
of the formant frequencies will not reflect the actual differences and
similarities in vowel qualities. Rather, the researcher will make an
attempt to compare the relative positions of the vowels on the
formant charts.
It is obvious from the charts that both [i] of Vietnamese and of
General American have noticeable similarities. They are the most

66. 60
close and front vowel in both systems. Despite this, the Vietnamese
vowel appears to be higher than the American counterpart.
In the front positions, Vietnamese has two other vowels, [e] and [ɛ],
while General American has three, [i], [ɛ], and [æ]. In spite of the
very different represented phonetic symbols, [e] in Vietnamese, like
in hết and [i] of American, as in hit, show considerable quality
equivalence. The situation is much the same for the other pair in
consideration: [ɛ] of Vietnamese and [æ] of American English. They
are both a short distance lower on the charts. The remaining
American vowel [ɛ] is deviant from the group. It is farther to the
central, and also more open.
The central area of the chart also deserves careful attention. Asides
from appearing to be closer, the Vietnamese [ɯ] and the American
counterpart [ɝ] show some important similarity. It must be noted,
though, that the additional r quality may make the sounds sound less
similar. [ʌ], [ɤ]and [ɤ̆], on the other hand, show strikingly close
quality.
The vowel [ɑ] of American English and [a] of Vietnamese are both
very open, but the latter is considerably farther to the front area.
In the back area of the chart, both Vietnamese and American English
have a vowel represented as [u] and another vowel, as [ɔ]. They

67. 61
also occupy much the same positions on the chart. The qualities of
each vowel in these pairs are, therefore, expected to be very alike.
The remaining vowel, [o] in Vietnamese, and [ʊ] in American
English, are quite different. The first vowel is much lower, and is
slightly more back.

68. 62
Chapter 5 CONCLUSION
5.1. The main findings on the acoustics of Hanoi Vietnamese
monophthongs
In this study, the researcher has made an attempt to give a
description of the monophthongs in Hanoi Vietnamese, based on the
acoustic measurements of the formant frequencies. Despite the
shortcomings of the research, it has discovered important results.
The measurements and comparison of F1 and F2 among the
monophthongs have pointed out that there is not a vowel which has
been traditionally described and represented by /ɛ̆/ in some accounts
in literature. The average formant frequencies values have
demonstrated that the qualities of this vowel is much the same as
those of /ă/ and /a/. It has also been highlighted that the latter vowel
is contrasted from the previous essentially by the vowel duration.
This strongly supports the claims made by Đoàn (2000) that duration
is the distinguishing features of these vowels. As a result, it is
suggested that /ɛ̆/ and /ă/ are equated, and the later phonetic symbol
will be arguably able to represent both.
The situation is subtly different for /ɤ̆/ and /ɤ/. The former vowel has
slightly higher F1 and F2 than the later vowel, featuring its quality as
being more front and more open. This has somewhat gone against
previous studies which maintain that these vowels are of the same
quality, but different in terms of the duration. Despite this fact, it

69. 63
must be acknowledged that they are fundamentally similar, and that
the duration contrast clearly plays an important role in distinguishing
one from the other. The formant chart (vowel chart) has also added
that they are vowels being typically central.
Another pair of vowels, /a/ and /ă/, have also been shown to have
radical similarity in qualities. While the former is marginally more
front and more close, it must be accepted that the degree of similarity
is significant. It should also be noted again that it is the duration
difference that distinguishes them from each other.
The last vowel whose description has generated heated debate among
phoneticians is /ɯ/. The measurement of F1 and F2, and the position
it occupies on the formant chart suggests that this is a close central
vowel.
5.2 The monophthongs of Hanoi Vietnamese and General
American English in comparison
This research has also been set out to provide a comparison between
the relative positions of the monophthongs in Vietnamese and
General American English on the formant charts. The result is of
keen interest and is highly suggestive in language education.
It is interesting that many monophthongs in both languages share
their position with a sound of the other language on the format chart,
despite the different phonetic symbols which represent them. The
Vietnamese /e/ is surprisingly similar to the American /i/, although

70. 64
the former appears to be more open. In the same way, the vowel /æ/
in American English, which has been shown to be substantially
different from the counterpart of RP, shares its important qualities
with /ɛ/ of Vietnamese. /ʌ/, /u/, and /ɔ/ are three other vowels
which have strikingly similar sounds in Vietnamese, being /ɤ/, /u/,
and /ɔ/ respectively. In this group, that /ʌ/ and /ɤ/ share their
qualities has been mentioned in literature.
5.3 The limitations of the study and suggestions for further
research.
Despite its achievements, there are important limitations in the
current study, which have been pointed out to some extent
aforementioned.
The spectrograms have failed to present the formant frequencies of
the vowel [ɔ̆] in measurable contours. This vowel, as described in
the chapter of research methods, is realized in the chosen word óc.
The failure is due to the limited distribution of the vowel, as being
accounted for in literature. The consonant following [ɔ̆] has
shortened it significantly, resulting in the very short formant
contours. Added to this, this consonant ([k]), also has great influence
on the vowel’s formants, changing its value considerably,
aggravating the situation.

71. 65
As it has been pointed out, it is possible that the vowel in anh is not
purely [ă], but there is possibly a glide to a second vowel,
characterizing an [i] before the influence of the following consonant
can take effect. However, as this consonant, as analyzed, has its
formant frequency values almost equal to those of [i], the attempt to
prove that [i] exists has been of little success.
Ladefoged (2011, p.212) has pointed out that although the absolute
values of the formant frequencies between men and women, between
children and adults are generally different, due to the anatomical
differences, the relative positions of the vowel on the charts,
indicating how the vowels are articulated, are similar. Nevertheless,
if this thesis had investigated the pure vowels produced by two other
groups, men and children, the research results would have been more
insightful.
Finally, the study has not described all the dimensions of the
Vietnamese monophthong qualities. Discussion on the findings of the
research, as well as the review of literature has suggested that there
are pure vowels in Vietnamese whose qualities cannot be described
based solely on the qualities of being close or open, front or back, or
on the frequencies of the first two formants. It is the duration that
plays a crucial part. This study has not investigated this dimension.

72. 66
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http://www.linguistics.ucla.edu/people/grads/billerey/PlotFrog.htm.
Clark, M. J, Hillenbrand, J, et al (1995). Acoustic characteristics of
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Đoàn, T. T. (2000). Ngữ âm Tiếng Việt. Hà Nội: Nhà xuất bản Đại học
Quốc gia Hà Nội.
Gimson, A.C (2008). Pronunciation of English. Oxford: Oxford
University Press.
Gomez, E.T. (2012). British and American English Pronunciation
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article&id=332&Itemid=51
Johnson, K. (2005). Speaker normalization in speech perception.
Retrieved from
http://www.phonetik.unimuenchen.de/~reichelu/kurse/perz_fort/liter
atur/JohnsonHSP2005.pdf.
Johnson, K., Ladefoged, P. & Lindau, M. (1993) Individual
differences in vowel production. Journal of Acoustical Society of
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Ladefodged, P & Johnson, K. (2011). A Course in Phonetics. Boston:
Wadsworth.
Ladefoged, P. (2003). Phonetic Data Analysis: An Introduction to
Fieldwork and Instrumental Techniques. Oxford: Blackwell
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Ladefoged, P. (2005). Vowels and Consonants. Oxford: Blackwell
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Ladefoged, P. (1996). Elements of Acoustic Phonetics. Chicago:
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74. 68
Appendix 1: The ethic form
Phiếu chấp thuận tham gia vào nghiên cứu
Tên đề tài: Phân tích âm học so sánh nguyên âm đơn tiếng Việt Hà Nội và
tiếng Anh Mỹ Phổ thông
Tôi đã đọc tờ phiếu thông tin cũng như được tác giả nghiên cứu giải thích về các
thông tin liên quan đến đề tài này.
Tác giả đã giải thích một cách rõ ràng về mục đích của đề tài, yêu cầu với những
người tham gia nghiên cứu, đồng thời cũng trả lời thỏa mãn các câu hỏi từ phía tôi.
Tôi đồng ý với kế hoạch đã được đưa ra trong Phiếu thông tin liên quan đến quá
trình tham gia nghiên cứu của mình.
Tôi hiểu rằng việc mình tham gia vào đề tài này là hoàn toàn tự nguyện và tôi cũng
có quyền dừng tham gia quá trình nghiên cứu vào bất cứ thời điểm nào tôi muốn.
Tôi đã nhận được một bản Phiếu chập thuận này cùng tờ phiếu thông tin đi kèm.
Tên:
Chữ ký:
Ngày tháng:
Đại học Ngoại ngữ - Đại học Quốc gia Hà Nội
Khoa Sau Đại học

75. 69
Appendix 2: The stimuli
Phần 1
Hướng dẫn:
Đọc đoạn giới thiệu về truyện cổ tích Tấm Cám dưới đây. Giọng đọc của bạn sẽ
được ghi âm.Trước khi đọc, bạn có 10 giây để chuẩn bị.
“Tấm Cám là một câu chuyện cổ tích Việt Nam thuộc thể loại truyện cổ tích thần kì,
phản ánh những mâu thuẫn trong gia đình, cuộc đấu tranh giữa cái thiện và cái ác,
cùng ước mơ cái thiện thắng cái ác của người Việt Nam.”
(Nguồn: Wikipedia)
Phần 2
Hướng dẫn:
Đọc mỗi từ/chữ cái xuất hiện dưới đây hai lần. Câu trả lời của bạn sẽ được ghi âm.
Trước khi đọc, bạn có 10 giây để chuẩn bị.
1. i
2. ê
3. e
4. anh
5. ư
6. u
7. ô
8. o
9. óc
10. ơ
11. ân
12. a
13. ay