Application of Rock Wool Sound-Absorbing Panels on Hangzhou Metro Line 7

The noise barriers constructed with rock wool sound-absorbing panels have been installed along the stations of Hangzhou Metro Line 7. This application has significantly reduced the nighttime noise levels in the vicinity of the stations, dropping from the original 62 decibels (dB) to 49 dB, which complies with the requirements specified in the Standard for Environmental Noise of Urban Areas. The use of rock wool sound-absorbing panels provides an effective solution for noise reduction in urban public transportation infrastructure.

1. Application Scenarios and Scope

The barriers are primarily deployed in the Xiaoshan section (e.g., between Xinjie Station and Kanshan Station), the ground and elevated sections of the Jiangnan segment, as well as noise-sensitive areas adjacent to residential communities, such as around station air vents and cooling towers.

A semi-enclosed composite noise barrier is adopted, with fully enclosed sections in specific areas. For station air vents and cooling towers, modular sound-absorbing enclosures consisting of "rock wool panels + perforated metal sheets" are used to balance ventilation and noise reduction requirements.

2. Selection and Technical Parameters of Rock Wool Sound-Absorbing Panels

Hydrophobic rock wool panels with a density of 100–120 kg/m³ and a thickness of 100 mm are selected, encased in 0.8 mm color-coated perforated steel sheets (with a perforation rate of ≥25%). The detailed parameters are as follows:

3. Construction and Noise Reduction Effect

Construction Process

The construction follows the sequence of: foundation anchoring → H-beam column installation → rock wool panel filling → panel fixation → sealing and anti-corrosion treatment. The installation cycle for a single section is ≤4 hours, suitable for nighttime construction windows.

Noise Reduction Results

• The noise level has been reduced by 13 dB, from 62 dB to 49 dB, meeting the nighttime limit of ≤50 dB for Class 2 areas specified in GB 3096-2008 Standard for Environmental Noise of Urban Areas.
• The compliance rate of nighttime noise levels at sensitive points reaches 100%, with noise complaints decreasing by more than 85%.

Structural Safety

The barriers can withstand a wind load of ≥0.7 kPa and meet the impact resistance requirements for metro operation safety.

4. Noise Reduction Principle and Technical Advantages

Noise Reduction Principle

• Porous Sound Absorption: The high porosity (>90%) structure converts sound waves into thermal energy, achieving a sound absorption coefficient of 0.8–0.95 for mid-to-high frequencies (500–4000 Hz).
• Mass Sound Insulation: The composite structure of high-density core material and panels blocks low-frequency noise through the mass law, with a weighted sound insulation index (RW) of ≥30 dB.
• Damping and Vibration Reduction: The flexible fiber structure weakens the transmission of solid vibrations, reducing secondary radiated noise from the structure.

Core Advantages

• Cost-Effectiveness: The total cost (materials + installation) ranges from 350 to 500 CNY per square meter, with a service life of ≥15 years, offering higher whole-life cycle cost performance than glass wool or polyester fiber panels.
• High Adaptability: The modular design allows for quick assembly and disassembly, suitable for curved and variable-section sections.
• Safety and Environmental Friendliness: Class A non-combustible, formaldehyde-free, and no harmful substances released during construction and use.

5. Promotion Value and Recommendations

Applicable Scenarios

This solution is suitable for metro elevated sections, ground station air vents, depot maintenance workshops, and especially areas adjacent to noise-sensitive targets (schools, hospitals, residential communities).

Optimization Directions

• Low-Frequency Enhancement: Adopt a double-layer rock wool + air layer structure to improve low-frequency noise reduction by 2–3 dB.
• Landscape Integration: Design a composite "noise barrier + green plants" system combined with landscaping to enhance both noise reduction and aesthetic appeal.

6. Conclusion

The application of rock wool sound-absorbing panel noise barriers on Hangzhou Metro Line 7 has achieved a 13 dB noise reduction and stable compliance through optimized material selection, structural design, and refined construction. This project verifies the effectiveness and economy of rock wool materials in noise reduction for urban rail transit, providing a standardized solution for similar projects.