CERN’s noise footprint and its impact on the Laboratory’s neighbours stem mainly from the infrastructure of its large accelerators. In 2019 and 2020, with the accelerator complex shut down, the noise source and profile were different. During this period of heavy maintenance and upgrades, noise resulted mostly from transport and worksite and civil-engineering activities.

Managing CERN's noise footprint

Noise measurements being taken at Point 1 of the LHC. (Image: CERN)

In the past, most CERN sites were in rural areas. With increasing urbanisation, housing has been constructed near to some facilities. To minimise the noise impact on the immediate neighbourhoods, the Organization has implemented noise mitigation measures, such as noise barriers and silencers to reduce noise during accelerator operation.

The majority of CERN’s surface installations are in France; in 2019, the Laboratory published a noise reduction policy and implementation strategy that was agreed upon with the French authorities. This policy was established using baseline measurements carried out in 2018 and includes both preventive and corrective measures. CERN is committed to restricting noise at its perimeter to 70 dB(A) during the day and 60 dB(A) at night at worst, complying with French standards for industrial plants. At most CERN sites, the noise level at the perimeter at night is close to or below 45 dB(A). An update of the policy is under way to better calculate the impact of multiple projects on the same site.

Action has been taken, in particular, to reduce noise from cryogenic equipment, which is vital for cooling the Large Hadron Collider (LHC) and can generate noise in the neighbourhoods closest to the LHC sites. To reduce this disturbance, two large noise silencers were installed on the cryogenic exhaust at Point 2 in France prior to the start of the cool-down operation. A noise campaign to evaluate the silencers’ efficiency was carried out, showing that the exhaust noise was well below the ambient noise of other CERN equipment.

Noise measurements

Every year, CERN carries out noise measurement campaigns at the perimeter of its sites. Measurements are carried out during daytime, night-time and weekends at around 200 locations, and the results are then compared to the 2018 baseline. During the period covered by this report, 2019 and 2020, occasional non-conformities were identified due to maintenance and consolidation activities, which were then corrected.

CERN is also evaluating the possibility of integrating an online monitoring system that carries out real-time measurements, allowing rapid intervention if needed.

In focus

Jordan Minier is an acoustic expert who started working at CERN in 2020 to ensure implementation of the noise policy.

— What is CERN’s approach to controlling the noise of its projects?

JM: In addition to carrying out routine noise measurements to evaluate the impact of existing installations, CERN has developed a strong noise-assessment process for each new project or new piece of equipment.

During the design phase of new projects, we use 3D modelling to predict their noise impact. The 3D modelling uses input from CERN’s existing buildings, sensitive receptors and noise source information. This allows us to predict noise levels at the sites’ perimeters and at each sensitive receptor location. Noise characterisation and 3D modelling are also used for implementing noise mitigation measures for existing buildings. All of the calculations are made in accordance with ISO 9613.

Based on the 3D modelling results, CERN develops mitigation measures and design changes to ensure that the noise remains below the limit set in the noise reduction policy.

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