Herein, the effects of changes in acoustic and non-acoustic factors on public health and reactions were assessed using two follow-up investigations; this was achieved after three surveys were conducted on the impact of the step change in noise caused by the increased number of flights at the Noi Bai International Airport in Hanoi (Vietnam) after the new terminal building was opened to the public. Exposure-response relationships established in the follow-up studies were less in number than those established in 2015 after the step change had occurred, and were almost similar to the relationship established in the survey conducted before the step change; however, these relationships were significantly greater than those established in the European Union position paper. Comparisons between respondents with high blood pressure and insomnia ratios at different noise level ranges showed that there is no significant association between ratios of high blood pressure and day-evening-night noise levels; however, an exposure-response relationship was discovered between insomnia and night-time noise levels. Non-acoustic factors such as noise sensitivity, sound insulation capacity of houses, and length of residence were found to curb the respondents’ annoyance, insomnia, and high blood pressure. Thus, an improvement in residence quality and a restriction on nighttime flight operation is necessitated.

There have been many arguments about findings of an increase in noise annoyance over time and a recommendation of stricter limits on aircraft noise levels to protect the health of residents around airports. It is crucial to examine if the established exposure–response relationship is suitable for designing future aircraft noise regulations. This study was focused on identifying changes in response to noise over time by comparing community responses from two surveys conducted in 2008 and 2019 at Tân Sơn Nhất (TSN) international airport. Annoyance was found to significantly reduce in 2019 compared to 2008; however, changes in sleep quality were relatively small. Unexpectedly, a gradual increase in the annoyance due to aircraft noise was not found. Results of multiple regression analysis indicated that differences in the reaction of the residents to noise in the two studies were significantly attributed to nonacoustic factors. Noise sensitivity and dissatisfaction with the living environment (e.g., inconvenience in accessing workplace) considerably affect noise annoyance, whereas noise sensitivity, age, and dissatisfaction with the green environment of living areas affect sleep quality. These findings suggest the fulfillment of desired living environment as effective measures for mitigating noise impacts on residents in the vicinity of busy airports.

The change in the self-reported health status of residents associated with the reduced aircraft noise around Tan Son Nhat airport (TSN) after the epidemic outbreak in early 2020 was investigated in three stages. Stage 1 is pre-outbreak when the airport was operating at its highest capacity. Phases 2 and 3 are three months and six months after the stop of international flight operation implemented in March 2020. Data on the residents' health status was obtained from face-to-face interviews. The questionnaire items were composed of Noise annoyance questions using the 11-point ICBEN scale, the Total Health Index, Health and lifestyle questionnaire, Depression Scale revised questionnaire, and questionnaires to identify insomnia, hypertension, and hearing loss. Other factors related to living conditions such as education, income, or housing were also collected as health adjustment factors. The noise levels of phases 2 and 3 were estimated by updating the noise contour map of phase 1 using the TSN airport's operation data in corresponding periods in 2020. This study provided evidence relating to variation of the residents' health status due to the noise situation change.

Many models have been proposed to clarify the interactive effects of acoustic and non-acoustic variables on human perception of noise. Due to the corona pandemic, all flights were closed at the end of March 2020, causing an unprecedented change in the acoustic environment around Tan Son Nhat Airport (TSN). Before the outbreak, TSN was the busiest airport in Vietnam and had severe noise problems. This study focused on determining how acoustic and non-acoustic factors affect community health before and after this change. Approximately 1200 responses were obtained from surveys conducted in 12 residential areas around TSN in 2019 and 2020. Structural equation models (SEM) for noise annoyance and insomnia were developed by linking the questionnaire items of the social surveys. The first effort aims to achieve a common model of noise annoyance and insomnia corresponding to community response to noise before and after the change. It has been found that the degrees of annoyance and insomnia were not reduced, as expected, but increased in 2020. The final constructed SEM indicates that acoustic and non-acoustic factors affected the community health in different structures before and after the noise reduction.

The travel restrictions caused by the epidemic outbreak in early 2020 worldwide have caused many changes in all aspects of life, especially in the acoustic environment. This study examines the impact of this environmental change at Tan Son Nhat International Airport (TSN), the largest airport in Vietnam, by comparing the situations before and after the airport stopped operating all international flights in March 2020. The after-the-change survey was conducted in 2 phases, June and September 2020, three months and six months after the stop decision. The number of flights observed in August 2019 was 728; this number is 413 and 299 for the two surveys in 2020. The range of noise levels estimated for 12 sites around TSN decreased from 63-81 dB in 2019 to 32-67 dB in June 2020 and 33-69 dB in September 2020. At the same aircraft noise level, the percentage of highly annoyed (% HA) and the percentage of insomnia (%ISM) in the 2020 survey are higher than those in the 2019 survey. The comparison results of reaction to noise before and after the TSN's noise change indicated an increase in negative responses to noise might happen in the increased noise and reduced noise situation.