Assessment of ventilation noise impact from metro depot with over-track platform structure on workers and nearby inhabitants.

In order to alleviate the shortage of land use accompanied with urbanization, over-track building complexes above metro depots are developed rapidly in China, resulting in the larger mechanical ventilation needs in the metro depot. Excessive noise exposure caused by the huge ventilation system will bring serious impacts on the health of workers in the metro depot. This research intends to evaluate the noise annoyance in the metro depot and the noise influences on adjacent residential buildings by the ventilation system. A questionnaire survey of 100 people working in a metro depot of Guangzhou Metro Line 6 was conducted, and field measurements inside the metro depot and inside adjacent residential buildings were carried out. The environmental noise level in the metro depot and the ventilation fan-induced noise level inside adjacent residential buildings exceed the corresponding criterion limit of China. Dose-response relationship modeled by logistic function was used to assess the noise annoyance, which is found underestimating the percentage of "Annoyed" (% A) and percentage of "Little Annoyed" (% LA) of staffs in the metro depot, especially for the % LA. This may be attributed to the reducing reliability of dose-effect curves as the Ldn is higher than 65 dB(A). In order to alleviate the noise impact, noise-controlling measures need to be took. However, traditional noise-controlling measures cannot solve low-frequency noise disturbance.