Xây dựng chính sách nhiễu Việt Nam và toàn cầu, các cuộc điều tra xã hội về ứng phó của cộng đồng với tiếng ồn máy bay và tiếng ồn kết hợp từ máy bay và đường giao thông đã được thực hiện tại thành phố Hồ Chí Minh từ tháng Tám đến tháng 9 năm 2008 và tại Hà Nội từ tháng Tám đến tháng Chín 2009. Tổng cộng, 1562 và 1397 phản ứng thu được tại thành phố Hồ Chí Minh và Hà Nội, tương ứng. Tiếng ồn máy bay được đo trong bảy ngày liên tiếp, và tiếng ồn kết hợp được đo trong 24 giờ. Tiếp xúc với máy bay và tiếng ồn kết hợp dao động 5371 dB và 7383 dB L den tại thành phố Hồ Chí Minh và 4861 dB và 7082 dB L den tại Hà Nội, tương ứng. Đường cong liều đáp ứng cho tiếng ồn máy bay cho Việt Nam được thành lập và trang bị lên đường cong cho Liên minh châu Âu. Cho tiếp xúc với tiếng ồn như nhau, không ít phiền toái tiếng ồn máy bay tại Hà Nội cao hơn ở thành phố Hồ Chí Minh vì mức độ tiếng ồn xung quanh thấp hơn tại Hà Nội.
Trang 1Community response to aircraft noise in Ho Chi Minh City and Hanoi
Thu Lan Nguyena,⇑, Takashi Yanoa, Huy Quang Nguyena, Tsuyoshi Nishimurab,1, Hiroaki Fukushimab,1, Tetsumi Satoc,2, Takashi Moriharad,3, Yoritaka Hashimotoe,4
a
Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, 860-8555 Kumamoto, Japan
b
Graduate School of Engineering, Sojo University, 4-22-1 Ikeda, 860-0082 Kumamoto, Japan
c Faculty of Engineering, Hokkai Gakuen University, Minami 26-Jo, Chuo-ku, 064-0926 Sapporo, Japan
d
Ishikawa National College of Technology, Kitachujo Ta-1, Tsubata, Kahoku, 929-0392 Ishikawa, Japan
e
Faculty of General Information, Okayama University of Science, Ridai-cho 1-1, Kita-ku, 700-0005 Okayama, Japan
a r t i c l e i n f o
Article history:
Received 1 November 2010
Received in revised form 21 March 2011
Accepted 6 May 2011
Available online 31 May 2011
Keywords:
Aircraft noise
Dose–response relationships
Developing country
a b s t r a c t
To formulate Vietnamese and global noise policies, social surveys on community response to aircraft noise and combined noise from aircraft and road traffic were carried out in Ho Chi Minh City from August
to September 2008 and in Hanoi from August to September 2009 In total, 1562 and 1397 responses were obtained in Ho Chi Minh City and Hanoi, respectively The aircraft noise was measured for seven succes-sive days, and the combined noise was measured for 24 h Aircraft and combined noise exposures ranged from 53 to 71 dB and 73 to 83 dB Ldenin Ho Chi Minh City and from 48 to 61 dB and 70 to 82 dB Ldenin Hanoi, respectively The dose–response curve for aircraft noise for Vietnam was established and fitted onto the curve for the European Union For the same noise exposure, the aircraft noise annoyance in Hanoi was higher than that in Ho Chi Minh City because of the lower background noise level in Hanoi
Ó 2011 Elsevier Ltd All rights reserved
1 Introduction
Noise policies are broad in scope They must include at least
exposure limits and an action plan of noise abatement as well as
expenses and payment that cover many fields of technical, social,
and economic sciences Community noise-control policies and
guidelines on mitigating noise have been laid down in many
devel-oped countries, especially in Europe[1–3] Boegli et al.[4]
intro-duced a noise abatement policy consisting of six basic principles
in which exposure–response relationships were defined as the
base principle of the framework Miedema and Vos[5]presented
exposure–response relationships for three transportation noise
sources These strongly affected the recommended curves in
suc-cessive EU position papers in 2002 (e.g., [1]) and then affected
EU noise regulation In 1999, to facilitate global coverage and
applicability, the Guidelines for Community Noise (WHO)[6]were
prepared to improve guidance at the national and regional level
The guideline values were given for specific environments, for example, a criteria level that is defined to cause a serious annoy-ance during daytime and in the evening for the outdoor living area
is 55 dB (LAeq) However, it has been pointed out in many studies that community response to noise was affected by non-acoustic factors such as culture, climate, lifestyle, and house type [7–9] Hence, a question arises as to whether the findings of previous studies, which were obtained mainly for developed countries, are applicable to the rest of the world, especially developing countries Many papers on noise policies in developing and emerging coun-tries were presented by Finegold and Schwela[10] They empha-sized a concern about whether the approaches being taken by western governments are applicable for implementation in devel-oping and emerging countries Indeed, a special effort was said to
be needed in order to better understand the differences between
‘‘developed’’ and ‘‘developing and emerging’’ countries and the implications of these differences in implementing adequate noise control approaches Vietnam is the second most populous country
in Southeast Asia with 31.7 million people living in urban areas accounting for 37% of the national population The impact of mar-ket-based economic transformation and its pace have severely af-fected Vietnam’s transportation conditions, resulting in an increasing volume of traffic and much noise being emitted from vehicles The involvement of Vietnam will contribute to the knowl-edge of the situation of developing and emerging countries in terms of environmental noise in the world It is supposed to be a meaningful voice when global policies are discussed
0003-682X/$ - see front matter Ó 2011 Elsevier Ltd All rights reserved.
⇑Corresponding author Address: Kumamoto University, Graduate School of
Science and Technology, Department of Architecture, 2-39-1 Kurokami, 860-8555
Kumamoto, Japan Tel.: +81 96 342 3560.
E-mail addresses: linh2lan@gmail.com (T.L Nguyen), yano@gpo.kumamoto-u.
(T Nishimura), sato@arc.hokkai-s-u.ac.jp (T Sato), morihara@ishikawa-nct.ac.jp
(T Morihara), hashimoto@archi.ous.ac.jp (Y Hashimoto).
1 Tel.: +81 96 326 3605.
2
Tel.: +81 11 841 1161.
3
Tel.: +81 76 288 8185.
4 Tel.: +81 86 256 9634.
Contents lists available atScienceDirect
Applied Acoustics
j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / a p a c o u s t
Trang 2for measuring noise at workplaces in manufacturing areas’’ It took
until 1988 for the first specific data on community noise exposure
measured in Hanoi, the capital of Vietnam, to be published
How-ever, documented data are very limited with only three noise
val-ues available during a day—average level for the rush hour in the
morning, rush hour in the afternoon, and all day In total, 41 noise
standards have been promulgated in Vietnam up to November
2009 These standards have mainly focused on acoustic
measure-ment methods and noise emitted by particular vehicles and
ma-chines Community noise is mentioned in only one standard—
TCVN 1549-1998 This standard regulates the maximum permitted
noise level in public and residential areas irrespective of the
sources of that noise These standards are constructed based on
the experience of western countries and Japan Actual exposure
data measured in two major cities in Vietnam, Hanoi and Ho Chi
Minh City, were shown to exceed those regulated in these criteria
by 8–33 dB The application of these standards is indeed very
lim-ited since they were not constructed based on actual figures from
Vietnam and were not accompanied by the documents of
cooper-ation or pays principles
Therefore, the first and also the most important thing needed to
do to initiate the establishment of noise policy in Vietnam is to
propose dose–response relationships based on actual data of
expo-sure and community response in Vietnam In order to meet this
requirement, community response to transportation noise has
been investigated in Hanoi and Ho Chi Minh City, since 2004 It
has been found that the Vietnamese were less annoyed by road
traffic noise by about 5 dB than European people[11] The dose–
response relationships for the Vietnamese were established for
road traffic noise exposure and annoyance response The present
study, which assesses the effects of another type of transportation
noise, that is, aircraft noise, is essential to generate a database for
formulating Vietnamese and global noise policies
Along with the rapid development of road traffic, another
sec-tion of Vietnam’s transportasec-tion network, the civil aviasec-tion market,
is now in a phase of strong and rapid growth The civil aviation
market is expected to carry 84 million passengers per year by
2020[12] The existence of many residential areas in the vicinity
of almost all airports in Vietnam has made aircraft noise, together
with road traffic, a main noise source that is causing adverse effects
on the quality of Vietnamese life This study, which analyzes the
impact of aircraft noise not only as a single source but also as a
combined source together with road traffic noise, can contribute
to the evaluation of a mixed noise environment
Vietnam The objectives of this study are (i) to propose a represen-tative dose–response relationship for aircraft noise annoyance in Vietnam and (ii) to assess the acoustic and non-acoustic factors moderating the response difference among sites and between the two cities
2 Methods 2.1 Survey sites The two cities chosen for the surveys are the busiest major metropolitan areas in Vietnam In these cities, the effects of trans-portation noise on the health of the urban population continue to grow The increase in transportation noise is due to rapid urbaniza-tion and industrializaurbaniza-tion Tan Son Nhat Airport, Vietnam’s largest international airport with around 200 takeoffs and landings per day, is located inside a crowded residential area of Ho Chi Minh City with busy commercial streets, as shown in Fig 1 Noi Bai Airport is the second largest international airport in Vietnam and provides aviation transportation for the capital city, Hanoi The handling capacity of Noi Bai Airport is less than half of Tan Son Nhat Airport[13] Noi Bai Airport is located 45 km from downtown Hanoi and is in the hub of many national arterial roads and industrial zones (Fig 2)
Ten residential areas were selected around Tan Son Nhat Air-port including eight sites under the landing and takeoff paths of aircraft and two other sites laying to the north and south of the runway (Fig 1) Nine sites were selected around Noi Bai airport including seven sites under the landing and takeoff paths of aircraft and two sites to the south of the runway (Fig 2) The site selection was intended to reflect the aircraft noise exposure covering loca-tions at various distances from and in direcloca-tions relative to the airport
Because this study was intended to investigate aircraft noise both as a single and as a combined source, all the sites except Sites
9 and 10 in Ho Chi Minh City and Site 6 in Hanoi were selected from residential areas that had roads passing through them The houses facing the roads were selected for the combined noise survey, and those set back from the road were selected for single aircraft noise surveys, as shown inFig 3 Sites 9 and 10 in Ho Chi Minh City were located inside a large residential area, whereas Site 6 in Hanoi is a rural village with no major roads passing through it Only the sur-vey on aircraft noise was conducted at these three sites
Trang 32.2 Social surveys
Social surveys on community response to aircraft noise and
combined noise from aircraft and road traffic were conducted
around Tan Son Nhat Airport in Ho Chi Minh City from August to
September 2008 and around Noi Bai Airport in Hanoi from August
to September 2009 The surveys were conducted by face-to-face
interviews during the daytime on weekends To guarantee a
bal-ance of males and females and generations, fathers, mothers, and
others whose age was over 18 were selected
The design of the questionnaire followed Technical
Specifica-tion ISO/TS 15,666, in which an internaSpecifica-tionally standardized
interview method for the assessment of noise annoyance by
socio-acoustic surveys is described That is, the questionnaire is
la-beled as ‘‘Survey on Living Environment’’ The questionnaire was
not only on noise but also various components of the living
environment The content of the questionnaire is summarized in
Table 1 Two versions of this questionnaire were used in this
study—one for the single noise survey and the other for the
com-bined noise survey Both questionnaires contained queries on
housing, neighborhood environment, noise annoyance, interfer-ence with daily activities, sensitivity, attitude towards transporta-tion, and socio-demographic items The questionnaire used in the combined noise survey, besides containing similar questions to those in the single noise surveys, had additional questions related
to the annoyance caused by road traffic and combined noise In the questionnaire, two scales—5-point verbal and 11-point numeric— constructed according to the ICBEN (International Commission on Biological Effects of Noise) method were used to evaluate the respondents’ noise annoyance[14] The wordings used in both questionnaires are shown inAppendix A
2.3 Noise measurements Since there was a lack of available noise data in Vietnam, all noise databases for this study were compiled using field measure-ments Noise measurements were performed in Ho Chi Minh City from September 22 to 29, 2008, and in Hanoi from September 10
to 17, 2009, by applying the same method in both cities Aircraft noise exposure was measured every 1 s for seven successive days
by using sound level meters (RION NL-21 and NL-22) in the areas
of the single noise surveys Microphones covered with omni– weather wind screens were positioned on the rooftops of the high-est houses in the areas—1.5 m above the roofs and at least 1 m away from any other reflecting surface Flight numbers and condi-tions were obtained from the Airport Office at each airport The combined noise of aircraft and road traffic was measured every 1 s for 24 h in the areas covered in the combined noise sur-veys Since we selected a representative day for noise measure-ment in a moderate season in a year, the effect of traffic volume fluctuation and meteorological factors might be negligible The measurements were performed at reference points that were 1.2 m high and 2.5–5 m away from the road shoulders The refer-ence points were selected at the average distances from the roads
to the house facades However, we measured road traffic noise at points on road shoulders in open areas, e.g., vacant lots along the road, without the effects of reflection from houses or other objects Traffic volume was counted by panel-replaying the video record-ings for 10 min every hour Road traffic noise metrics were calcu-lated by energy subtraction of aircraft from combined noise metrics
3 Results and discussion 3.1 Results of social surveys The outline of the surveys is summarized inTable 2 In total,
1562 and 1397 respondents participated in the surveys in Ho Chi
Fig 2 Map of survey sites in Hanoi Source: Google Earth.
Fig 3 Illustration image of areas for the surveys on single and combined noise.
Source: Google Earth.
Trang 4Minh City and Hanoi, respectively In Ho Chi Minh City, there were
880 respondents in the single noise survey and 682 respondents in
the combined noise survey These numbers in Hanoi were 824 and
573, respectively The response rates were very high in both cities:
the total response rates for the aircraft and combined noise surveys
were 88% and 85% in Ho Chi Minh City and 91.6% and 76.4% in
Ha-noi, respectively
Some of the socio-demographic factors of the surveys in both
cities are summarized and compared with the demographics of
the Vietnamese population inTable 3 The ratio of males to females
in all surveys was well balanced and comparable to the ratio
ob-tained in the Vietnam population census For the two surveys,
89% and 92% of respondents in Ho Chi Minh City were in the age
range from 20 to 60; corresponding figures for Hanoi were 88%
and 90% All of these percentages were slightly higher than that
ob-tained in the Vietnam population census (84%) Employed
respon-dents constituted 45% and 39% in the two surveys in Ho Chi Minh
City, and 62% and 55% in Hanoi Although there is a slight
differ-ence in ratio between the socio-demographic factors of the survey
sites and the Vietnam population census, the respondents of all the
surveys seem to represent the typical Vietnamese people
3.2 Traffic volumes and noise exposure
Figs 4 and 5show the average number of flights in Ho Chi Minh
City and Hanoi It should be noted that between 9 and 10 pm, more
landings than takeoffs were observed in both cities The fluctuation
of traffic volumes at all sites for 24 h in both cities is shown inFigs
6 and 7 There seemed to be considerable differences in traffic
den-sity among the surveyed sites in Ho Chi Minh City and Hanoi The
largest traffic volume in Hanoi was over 3000 pass-bys per hour at
Site 8 This was not comparable to that observed at the reference
point of Site 2 in Ho Chi Minh City which was nearly 40,000
pass-bys per hour Motorbikes formed the bulk of the traffic in both cities, accounting for 92% of the total traffic in Ho Chi Minh City and 72% in Hanoi
Tables 4–7show the noise metrics calculated for aircraft and combined noise exposures at all the sites in both cities The aircraft noise exposure range in Ho Chi Minh City was wider than that in Hanoi Aircraft and combined noise exposures were from 53 to
71 dB and 73 to 83 dB Ldenin Ho Chi Minh City and from 48 to
61 dB and 70 to 82 dB Ldenin Hanoi, respectively
The highest aircraft noise exposure level in Ho Chi Minh City (Lden= 71 dB) was found at Site 5, the closest site to the airport under the landing path Similarly, the highest level in Hanoi was
Housing factors House type; length of residence; area of first floor; comments on quality of housing
Residential environment Climate in the area; quality of residential environment
Annoyance From traffic noise, from air pollution; from neighbour; frequency of annoyance; annoyance in specific time and season; annoyance due to
vibration caused by traffic Interference on daily
activities
Listening, sleeping disturbance; disturbance while resting, talking, gardening Sensitivities, attitudes,
etc.
Sleeping with open window in certain season; time of going to bed and getting up in weekend and weekday; sleeping condition; sensitivity
to weather and environmental factors; attitudes to the use of transportation vehicles; using frequency; comments on safety Socio-demographic
variables
Occupation; length of period to stay at home; number of family members; age Questions answered by interviewers according to the respondents’ facts
Gender of respondents
Structural details of the
house
main structure; number of glass layers, frame types of windows and doors of the living rooms and bedrooms; direction of facing or not facing doors and windows
Table 2
Outline of social surveys on community response to aircraft noise in Ho Chi Minh City and Hanoi.
Street D Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 Site 10 Total
Ho Chi Minh City
Sample size
Hanoi
Sample size
Table 3 Some demographic factors of the surveys.
Items Ho Chi Minh City Hanoi
Aircraft (%) Combined (%)
Aircraft (%) Combined (%)
Demographics
of Vietnam a
(%) Gender
Age
Occupation
Students, housewives, retired, and unemployed
a General statistics office in Vietnam, ‘‘Statistical Date’’ http://www.gso.gov.vn/
Trang 5observed at Site 3 and Site 8 (Lden= 61 dB), which were the closest
sites under the landing and takeoff paths of aircraft, respectively
The lowest aircraft noise exposure (Lden= 53 dB) in Ho Chi Minh
City was obtained at Site 2, the second-farthest site from under a
landing path, whereas that of Hanoi was at Site 5 (Lden= 48 dB),
the site laying to the south of the runway
Tables 6 and 7show that the highest combined noise exposure
level was found at Site 2 in Ho Chi Minh City (Lden= 83 dB) and Site
8 in Hanoi (Lden= 82 dB) These sites were located along the
na-tional highways, which had much traffic volume with heavy
vehi-cles during the daytime The lowest combined noise exposure level
was obtained at Site 3 in Ho Chi Minh City (Lden= 73 dB) and at Site
1 in Hanoi (Lden= 70 dB) They were along local roads serving sep-arate residential areas
3.3 Dose–response relationships
A logistic regression function was applied to plot the dose–re-sponse curves for aircraft noise annoyance This was evaluated
by the percentage of people highly annoyed by aircraft noise in the single and combined noise surveys in Ho Chi Minh City and Ha-noi; the day–evening–night average sound level (Lden) was chosen
as the independent variable Following the European Union (EU) position paper[4], in which the cut-off point for the highly an-noyed was defined as the top 28%, the authors defined the top three categories of the 11-point numeric scale (top 27%) as highly annoyed
The dose–response curves for general annoyance in Ho Chi Minh City and Hanoi were plotted based on the data from the sin-gle and combined noise surveys and are shown inFigs 8 and 9, respectively Hanoi’s curves are higher than Ho Chi Minh City’s in both figures In other words, respondents in Hanoi were more an-noyed by aircraft noise than those in Ho Chi Minh City at the same noise level It is also worthy of note that except at Sites 3 and 4, the percentage of highly annoyed among sites in Hanoi was shown to
be only slightly higher than that in Ho Chi Minh City The sudden increase of annoyance at Sites 3 and 4 contributed to extending the gap between the curves of the two cities The cause of the sharp increase in annoyance at Sites 3 and 4 in Hanoi will be discussed in the following section
Effect Wald Tests were applied to obtain the probability of obtaining a greater Chi Square (p) and also the R2to all the logistic regression models drawn inFigs 8 and 9 The results indicated that
Lden of aircraft noise had a significant effect at p < 0.001 on the annoyance in both single and combined noise areas
Fig 10shows the relationships for general annoyance in Ho Chi Minh City and Hanoi using synthesized data from all surveys and compares it with the EU’s The 95% confidence interval was calcu-lated to estimate the distribution of highly annoyed respondents at each site surveyed The values of p shown inTable 8were proved for the significant effectiveness of the parameters of the model in
Fig 10 At the same noise level, the percentage of highly annoyed respondents in Vietnam was slightly higher than those in the EU
In other words, there is 2–3 dB difference between the two curves
at the same percentage of high annoyance
In addition to general annoyance, it is necessary to investigate the activity disturbance as another descriptor of the effects of
Time (h) Fig 4 Number of flights in Ho Chi Minh City.
0
2
4
6
8
10
12
14
Time (h) Takeoffs
Fig 5 Number of flights in Hanoi.
0
10000
20000
30000
40000
1 3 5 7 9 11 13 15 17 19 21 23
Time (h)
Site1 Site2 Site3 Site4 SIte5 Site6 Site7 Site8
Fig 6 Traffic volume in Ho Chi Minh City.
0 10000 20000 30000 40000
1 3 5 7 9 11 13 15 17 19 21 23
Time (h)
Site 1 Site 2 Site 4 Site 5 Site 8 Site 9
Fig 7 Traffic volume in Hanoi.
Trang 6aircraft noise on humans In this study, listening disturbance was
evaluated by a 5-point verbal scale, with the same modifiers as
the annoyance scale The cut-off point for activity disturbance
was defined by the top two points The logistic regression function
was also applied to plot the dose–response curves of percent
lis-tening disturbed with the daytime average sound level L
Aeq,-day(07:00–22:00) as the independent variable (Fig 11) Consistent
with the analysis of general annoyance, Hanoi’s curves are higher
than Ho Chi Minh City’s with a sudden increase of percent
disturbed at Sites 3 and 4 In addition to the results of general annoyance, this finding yields a question as to why the respon-dents in Hanoi were more annoyed or disturbed than those in Ho Chi Minh City at the same noise exposure
3.4 Difference in response among sites
In this section, the possible causes of high annoyance particularly at Sites 3 and 4 in Hanoi will be discussed through a
Table 5
Noise metrics calculated for aircraft noise exposure at all sites in Hanoi.
Table 6
Noise metrics calculated for combined noise exposure at all sites in Ho Chi Minh City.
Table 7
Noise metrics calculated for combined noise exposure at all sites in Hanoi.
Trang 7comparison with Sites 7 and 8, which have the equivalent noise levels Though respondents at Sites 3 and 8 were exposed to almost the same aircraft noise levels, 60.9 and 61.1 dB, respectively, those
at Site 3 were found to be more highly annoyed by aircraft noise than those at Site 8 as shown inTable 5andFig 8 The same find-ing was also gained between Site 4 (Lden= 56.3 dB) and Site 7 (Lden= 56.8 dB) These results suggest that annoyance is affected not only by noise exposure levels but also by other factors
It is noteworthy that Sites 3 and 4 and Sites 7 and 8 are, in pairs, located under the landing and takeoff paths, respectively In the questionnaire survey, the respondents were asked to indicate how frequently they were disturbed by the airborne vibration from aircraft (Table 9) The results showed that, in the aircraft and com-bined noise surveys, the residents at Sites 3 and 4 were more fre-quently disturbed by the airborne vibration from aircrafts than those at Sites 7 and 8
In addition, the frequency of use of airplanes by the respon-dents at each site was assessed As can be seen inTable 10, the percentages of respondents who did not use airplanes at all were 89% and 95% in the aircraft noise areas of Sites 3 and 4, while these were only 50% and 57% at Sites 7 and 8, respectively The differences are slightly smaller when considering combined noise areas at these sites Since sleep disturbance is also a main effect
of noise on humans, the time at which respondents went to bed was investigated (Table 11) The results indicated that, with the exception of the aircraft noise area of Site 8, more respon-dents at Sites 3 and 4 went to bed between 9 and 10 pm than those at Sites 7 and 8 In addition, there are more landings than takeoffs observed during this period of the night (Figs 4 and 5) These facts might cause higher sleep disturbances at Sites 3 and
4, which were under the landing path of the aircraft, than at Site
8 at the same noise level All the above reasons could be used to explain the higher annoyance found at Sites 3 and 4 than at the other sites
3.5 Difference in response between cities The results of previous studies indicated that individuals tended
to judge the annoyance of an unwanted sound in terms of its rela-tionship to background noise The background noise level, in this study, is defined as the 95th percentile (L95), as shown inTables 4–7 It can be easily observed that the background noise levels at almost all sites of Ho Chi Minh City are higher than at those of Ha-noi While the average L95values in Hanoi are 43 dB and 44 dB for single and combined noise surveys, respectively, they are 45 and
51 dB in Ho Chi Minh City The outstandingly larger traffic volume
in Ho Chi Minh City might yield the higher background noise level
0
20
40
60
80
100
Lden (dB)
Hanoi (Single noise survey) HCM (Single noise survey)
Fig 8 Dose–response relationships for general annoyance in single noise surveys.
Table 8
Estimated coefficients for the logistic equation of Fig 10
b 0 : Intercept.
b : Slope parameter of the logistic response function.
0 20 40 60 80 100
LAeq,day 7:00-22:00 (dB) Fig 11 Dose–response relationships for listening disturbance using synthesized data from single and combined noise surveys.
0
20
40
60
80
100
Lden (dB)
Hanoi (Combined noise survey)
Ho Chi Minh (Combined noise survey)
Fig 9 Dose–response relationships for general annoyance in combined noise
surveys.
0
20
40
60
80
100
Lden (dB)
Fig 10 The synthesized curve of Ho Chi Minh City 2008 and Hanoi 2009 surveys in
comparison with the EU’s curve.
Trang 8there It can be speculated that the noise of aircraft events in Hanoi
when the background noise levels are lower might be generally
more noticeable than in Ho Chi Minh City
Multiple logistic regression analysis was performed with high
annoyance as a dependent variable and independent variables
including Lden, L95, and City factor (Hanoi: 0 and Ho Chi Minh: 1)
All Lden, L95, and City factors were shown to be significantly
effec-tive for high annoyance The results are shown inTable 12
Pear-son’s correlation coefficients were calculated to measure the
relationship between aircraft annoyance and background noise
levels In addition, Lden and the 1st percentile (L1) were also
in-cluded in the analysis to compare the relationship between
differ-ent noise metrics and annoyance in Ho Chi Minh City and Hanoi
Lden represented the day–evening–night average aircraft noise,
while L1is used to give an indication of the upper limit of
fluctuat-ing aircraft noise Bivariate correlations were calculated between
those noise metrics and each of three variables—individual
annoy-ance score, average annoyannoy-ance score, and percent highly annoyed
(Table 13) The results showed that L95 was statistically
signifi-cantly correlated at the 0.01 level with individual annoyance score
evaluated by the respondents of all surveys No significant effects
were found between L95and average annoyance score and between
L95and percent highly annoyed
It is worth noting that the coefficients between L95and
annoy-ance were negative for single noise surveys but positive for
com-bined noise surveys These results indicate that at the areas
affected by a single aircraft noise the lower background noise level
yielded more annoyance This finding is consistent with the results
of previous studies However, the results for combined noise areas
showed that the annoyance becomes higher when the background
noise level increases This finding emphasized the role of back-ground noise level on the annoyance of respondents in Ho Chi Minh City and Hanoi The results drawn out from this study were inconsistent with the main findings of Fields[15] Fields’s study in-cluded data from a total of 32 social surveys conducted in North American and European countries However, all the surveys were conducted during the years from 1967 to 1990 According to the
‘‘ICAO Environmental Report 2007’’, aircraft noise has been re-duced by 20 dB within the last 25 years This means that the air-craft noise nowadays has become much quieter than before and can therefore be much more easily masked by background noise Moreover, the traffic situation in Vietnam was supposed to have distinctive characteristics Extremely high road traffic noise expo-sure existed even in the vicinity of the airports Furthermore, the road traffic noise was contributed to by a huge amount of motor-bikes but not cars or light trucks as in other countries These indi-cate different traffic situations in Vietnam compared with the countries investigated in Fields’s study Although Fields pointed out that only 3 of 16 findings suggested an important reduction
of annoyance with the presence of high ambient noise levels, the results found in this study fell into this exception Research on a similar topic in Korea by Lim et al.[16]also showed the same con-clusion as ours[16]
Table 10
Chi-square test of frequencies of respondents who do not use airplanes at all between sites under landing and takeoff routes.
Table 11
Chi-square test of frequencies of respondents who go to bed up to 22:00 between sites under landing and takeoff routes.
Table 12
Results of multiple logistic regression analysis for high annoyance.
Estimate 95% Confidence interval p
Dependent variable: HA(Dummy variable: 0–7:1, 8–10:0).
City: Hanoi(0), HCM(1).
Table 13 Pearson’s correlation.
Single noise surveys Combined noise surveys Individual annoyance score
Average annoyance score
% Highly annoyed
** Significant at the 0.01 level.
* Significant at the 0.05 level.
Trang 94 Conclusions
This study provided a broader knowledge on exposure
situa-tions as well as annoyance of aircraft noise in Vietnam Aircraft
and combined noise exposures ranged from 53 to 71 dB and 73
to 83 dB Ldenin Ho Chi Minh City and from 48 to 61 dB and 70 to
82 dB Ldenin Hanoi, respectively The dose–response curve for
air-craft noise for Vietnam was established and fitted onto the curve
for the EU It has been found that the curve for Vietnam was
2–3 dB lower than that for the EU at the same percentage of high
annoyance The non-acoustic factors such as frequency of
annoy-ance during exposures to airborne vibration, frequency of use of
airplanes, and time to go to bed seemed to moderate the response
difference among sites These factors yielded the highest
annoy-ance at the sites under the landing routes of aircraft Finally, for
the same noise exposure, the aircraft annoyance in Hanoi was
higher than that in Ho Chi Minh City probably because of the lower
background noise level in Hanoi
Acknowledgments
The authors appreciate the support of Ms T.B.N Nguyen from
Ho Chi Minh City University of Architecture for the social surveys
and noise measurements in Ho Chi Minh City and Professor D.N
Pham and Dr T.H Nguyen from Hanoi University of Civil
Engineer-ing for their vital help in conductEngineer-ing the surveys in Hanoi We also
appreciate the enthusiastic assistance of the students from both
universities, who supported interviews and noise measurements
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Appendix A
A Verbal annoyance question:
Thinking about the last 12 months or so, when you are here at home, how much are you bothered, disturbed, or annoyed by the follow-ing factors?
B Numeric annoyance question:
Thinking about the last 12 months or so, what number from 0 to 10 best shows how much are you bothered, disturbed, or annoyed by aircraft noise, road traffic noise, and combined noise of aircraft and road traffic?
(Aircraft noise)
(Road traffic noise)
(Combined noise of aircraft and road traffic)