Keywords: 
• noise control /
• cooling tower /
• ray-tracing technology

Abstract: Mechanical draft cooling towers are mostly used in cooling water circulation systems for central air conditioners in hospitals and other large public buildings. They usually generate high levels of noise, annoying the surrounding communities. In this paper, an engineering design and implementation study on noise control of large mechanical draft cooling towers is introduced and discussed based on a real project. The mechanical draft cooling towers involved are used by Zhangjiagang First People's Hospital and are composed of four groups of 16 towers. In the design stage, we first built a numerical model based on ray-tracing technology with commercial software (RAYNOISE). This model enables simulation of the noise impact around the towers before they are controlled, as well as prediction of community noise reduction around the towers after control engineering has been done. Second, we proposed a set of practical engineering measures for tower-noise control, based on the prediction support in the simulation model above. The engineering measures were implemented in sequence and detailed measurements were carried out on the community noise after the control engineering. The results show that, for community noise reduction, there was only a 3 dB difference between the prediction from the simulations and the measurements. They also showed that the community noise was reduced up to 10.8 dBA due to the control engineering. These indicate that, the noise control engineering in this case was shown to be successful and that noise control engineers could greatly benefit in the design stage, from reliable simulations based on ray-tracing technology.