The project is located on the rooftop of a China Construction Bank branch building in Zhangjiakou. Central air conditioning chiller units, circulating water pumps, and supporting pipelines are arranged on the roof. Equipment operation generates medium-to-low frequency noise that transmits downward through the air and building structure, disturbing internal bank office operations and affecting nearby residential areas. A noise reduction retrofit was required without altering the original equipment, while simultaneously ensuring unit heat dissipation and future equipment maintenance access.
Measurement Location | Before Mitigation | After Mitigation |
Rooftop Equipment Boundary | 85–92 dB (A) | 62–55 dB (A) |
Downstairs Office Area | 56–59 dB (A) | ≤ 53 dB (A) |
● Perforated Metal Sound-Absorbing Acoustic Panels: Used to build the peripheral soundproofing enclosure wall around the units. Combining sound insulation and absorption, they attenuate outward noise radiation from the equipment. Outdoor electrostatic spray coating provides corrosion resistance, making them suitable for Zhangjiakou's severe cold and open-air environment.
● Acoustic Louvers: Installed in modular batches on the ventilation facade to balance ventilation/heat dissipation while blocking noise leakage from the vents.
● Steel Acoustic Doors: Installed at maintenance access entryways, providing tight soundproof sealing. Paired with a maintenance platform, they fulfill routine unit servicing needs.
A prefabricated modular acoustic enclosure scheme was adopted. A steel support frame was erected on the roof, and perforated metal acoustic panels were assembled on-site with all gaps acoustically sealed. Multiple sets of acoustic louvers were installed on the ventilation and heat dissipation faces. Steel acoustic maintenance doors were installed along with maintenance steps. The entire design preserved the original pipelines and roof waterproofing. Post-construction re-testing and acceptance were conducted upon completion.
Upon project completion, noise levels met all target standards. The indoor office environment was significantly improved, and noise interference to nearby residents was eliminated. Acoustic louvers ensured proper unit heat dissipation without affecting equipment operating conditions. Steel acoustic doors facilitated convenient entry for operation and maintenance personnel. The entire assembly of metal components resists wind, snow, and low temperatures, allowing the project to successfully pass the client's final completion acceptance.
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