Effects of acoustic characteristics of combined construction noise on annoyance

Because the acoustic environments of construction sites include multiple noise sources from various construction machines, it is necessary to consider the influence of combined noise on annoyance. The aim of this study is to examine the effects of the acoustic characteristics of combined construction noise on annoyance. Six construction machines, including machines for foundation work (pile drivers, earth augers, and payloaders) and demolition work (breakers, bulldozers, and excavators) were selected as noise sources in construction sites, and auditory experiments were designed to quantify the annoyance caused by the machines' individual and combined noise. The results show that both individual and combined noise correlate well with the equivalent sound level (LAeq), but that the annoyance caused by combined noise is significantly higher than the annoyance caused by individual noise when LAeq increases over 65 dBA. Among the psychoacoustic measures, loudness is the most important in determining the annoyance caused by individual noise, whereas both loudness and roughness significantly impact the annoyance caused by combined construction noise. Ranges of an optimum stationary-to-mobile machine noise ratio between two construction machine noises are suggested to minimize the annoyance caused by combined noise. Optimum stationary-to-mobile machine noise ratio ranges usually include 0 dBA when reference construction noise levels (e.g., pile driver or breaker) are lower than 60 dBA, whereas the stationary-to-mobile machine noise ratio should be greater than 5 dBA as construction noise levels exceed 65 dBA. These findings provide useful information to establish effective noise management plans for combined noise sources in construction sites.