Conclusion

Given the research motivation presented in Section 1.3, this chapter began with a discussion on noise pollution and its control in Singapore. The discussion indicates that control of construction and road noise is challenging, given the high number of construction sites and roads that are near residential areas. This finding supports the motivation provided in Section 1.3 to examine policies to reduce construction and road noise in an urban setting.

To examine changes to noise abatement policies, a conceptual framework to conduct cost-benefit analysis of such policies was introduced. Since policy-makers do not know whether a proposed change to noise abatement policy results in potential Pareto improvements

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changes. Accounting for the welfare change attributable to public provision of noise abatement ensures that these result in a potential Pareto improvement.

To conduct the cost-benefit analysis, information on the marginal benefits and marginal costs of abating noise pollution is required. Further, the noise transfer function and the noise aggregation function are arguments in the marginal benefits function as noise is transferred from the source to the receptor and each receptor may be exposed to multiple noise sources. A change to noise abatement policy results in a potential Pareto improvement if the benefits arising from the public provision of noise abatement outweigh the costs of providing this measure.

The literature was reviewed to understand previous research on the marginal benefits and costs of noise abatement as well as the noise transfer and aggregation functions. The former two functions are informed by the economic valuation literature while information on the latter two are derived from acoustic engineering literature.

The literature review found that a key gap in the literature involved estimation of the marginal benefits of noise abatement. Markets do not exist for residents to express their preferences for publicly-provided noise abatement. Consequently, non-market valuation techniques are required to estimate the marginal benefits of policies that reduce the level of noise. The two main non-market valuation approaches are revealed preference studies and stated preference studies. In order to estimate marginal benefits, revealed preference studies require data on respondents’ demography and prior private investment into noise abatement, and, with the exception of specific countries, such information is not available publicly. Stated preference studies have also been conducted to estimate the marginal benefits of publicly- provided noise abatement. Previous stated preference studies described changes to noise levels textually.

Describing changes to noise levels textually is challenging. Unlike other environmental pollutants, noise pollution is measured in decibels, which is scaled logarithmically. Further, perceived loudness does not vary linearly with increased decibels. Consequently, a wide range of text-based descriptions has been developed to communicate changes in noise levels to respondents. However, no previous study has applied the techniques from audiology to estimate the preference for noise abatement by playing noise recordings to respondents.

This gap in the literature presents an opportunity to improve the methodology of stated preference surveys estimating the willingness-to-pay for public provision of noise abatement.

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Specifically, an audio-based stated preference survey questionnaire can be designed to estimate the willingness-to-pay for noise abatement. In a text-based survey, respondents need to read, understand, and interpret the descriptions provided in the questionnaire. However, if respondents were presented with audio recordings of different noise levels, they can directly perceive changes to the noise level and do not need to read and understand textual descriptions of noise levels. Since understanding the information provided in a stated preference questionnaire is necessary to ensure that respondents reveal their true preferences, an audio- based survey questionnaire may provide more accurate estimates of the marginal benefits of noise abatement.

The literature review indicates that residents’ preferences for noise abatement may be heterogeneous. First, prior spending on noise abatement measures can potentially affect the preference for public provision of noise abatement. Privately-provided noise abatement can substitute publicly-provided measures. However, the relationship between existing private provision of noise abatement and the willingness-to-pay publicly-provided noise abatement is an empirical question that has not been examined by previous studies.

Second, health status can affect the willingness-to-pay for health risk mitigation measures. Consequently, individuals’ hearing sensitivity may affect their willingness-to-pay to reduce noise abatement and protect their hearing by reducing noise levels. However, no previous study directly measured the hearing sensitivity of respondents and the relationship between hearing sensitivity and willingness-to-pay for publicly-provided noise abatement.

Finally, some previous stated preference studies have used different locations to describe changes in noise levels to respondents, suggesting that ambient noise levels affect preferences for noise abatement. Further, revealed preference studies used variation in the location of properties to estimate the effect of noise levels on property prices. Hence, another potential source of heterogeneity is ambient levels of noise, proxied by the distance between the noise source and respondents’ home.

The next chapter presents a list of research questions in light of the gaps in the literature presented in this chapter. These research questions are constructed based on the challenge of explaining changes to noise level with a text-based questionnaire and to understand the heterogeneous preferences for noise abatement.

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