Addressing data centre noise complaints through updated ordinances

However, these complaints are not limited to one country. In Japan too, noise is a regular focus of community pushback against data centre development, particularly in urban areas. This has already led to direct consequences for planning applications, causing delays and outright cancellations when communities and authorities are not satisfied that the data centre’s resultant noise will be adequately abated.

As community pushback continues to lead to data centre moratoriums, with New York instituting the first statewide ban in the US, we explore the regulatory challenges and potential revisions needed to balance community needs and industry interests.

1. Noise limits

Local communities often raise concerns about whether noise limits in ordinances are too high or fail to consider cumulative effects. Some US ordinances have tied limits to pre-operation ambient noise, but their effectiveness and practical application is disputed. In the US, industrial noise regulation varies by locality with minimal federal or state guidance, while the UK, EU, Australia, and Canada, along with organisations such as the WHO and World Bank, offer comprehensive frameworks. Reviewing these global standards can inform noise ordinances and guide decisions on limits, cumulative impacts, and analysis requirements, streamlining efforts by utilising established approaches.

2. Noise character

While ordinances typically limit noise in A-weighted decibels (dBA) over set periods, assessing additional factors like tonality, frequency content, impulsiveness, and amplitude modulation is key, as these can increase annoyance. Defining these traits allows for source penalties, effectively lowering limits for disruptive noises. However, addressing these issues during facility design through 1/3 octave emission assessments and selecting equipment to minimise tonal and low-frequency noise is often the best approach.

3. Noise calculation standards

Local communities have raised concerns about the credibility and accuracy of noise calculation methods used by data centre proponents, particularly regarding software like CadnaA or SoundPLAN. However, these platforms implement various ‘noise calculation standards’, making the choice of validated software less significant. The primary standard in North America is ISO 9613-2, which offers the best available model for outdoor noise prediction and was updated in 2024.

While alternative standards exist internationally, many critiques of ISO 9613-2 from opponents of data centre developments lack supporting evidence and adherence to established acoustical principles. Those developing or revising noise ordinances should review current standards to incorporate recent advancements. Authorities overseeing noise must clearly identify mandatory measurement and calculation standards to ensure consistent regulation. Additionally, choosing a credible noise calculation standard does not guarantee reliable project-specific predictions; effective modelling requires expertise, experience, and detailed input data.

4. Exceptional conditions

Understanding the limitations of noise propagation modelling is crucial, as no calculation standard is perfect. Models focus on average conditions, often overlooking rare events like temperature inversions or dense fog, which can cause real-world deviations.

For example, low-altitude cloud cover can reflect sound waves, affecting noise levels at a distance. However, this impact is minimal near the source, as the direct and reflected path lengths must be similar for this effect to be observed. Effects are typically felt several miles away, where noise levels are already low. Additionally, models like ISO 9613-2 may overpredict noise at large distances. Unlike chemical contaminants, sound dissipates over time, making cumulative effects over great distances rare and leading to excessive conservatism in predictions.

5. Noise source detail and proprietary information

The competitive nature of the data centre industry prompts some community representatives to argue that proponents misuse claims of proprietary information. However, disclosing vendor details or specifications can compromise competition for essential equipment like generators and chillers. While community groups desire transparency, it's vital to integrate this information into technical noise assessments without revealing sensitive details. Protecting proprietary information is crucial for maintaining competitiveness in the data centre sector.

6. Ambient noise and noise limit modifiers

Many noise ordinances fail to address existing ambient noise before a new facility’s construction. Some communities propose tying noise limits to pre-operation ambient levels, arguing that new facilities shouldn’t increase post-operation noise. This requires predicted sound levels to be significantly lower than existing ambient noise, which may be feasible in high existing ambient areas but often impractical elsewhere.

If a facility’s noise equals the pre-operation ambient at a measurement point, overall noise may increase by about 3 dB, typically seen as low impact unless the ambient level is already quite high. Local context, whether rural, urban, or suburban, is crucial. Standards like the British BS 4142 consider both project and ambient noise, emphasising that approaches must be nuanced and avoid oversimplification.

7. Ambient noise measurement

Proper measurement methodology, including metrics, locations, and duration, is essential for establishing project-specific noise limits. Clear guidelines on monitoring duration, variations, and sampling points ensure consistent application among stakeholders. Consistent measurements can be challenging due to fluctuations in noise levels influenced by time and long-term changes from new developments. Standards from ANSI, ASA, and ISO should be referenced in any new noise ordinance to guide measurement practices.

8. Compliance measurements

Compliance measurement methodologies must be clearly defined for consistent interpretation, specifying noise descriptors, minimum sample durations, sample quantity, variability, and timing.

Compliance limits should clearly identify the applicable noise descriptors as well as the applicable values for each time of day or day of the week.

Short-duration averages should not be taken as definitive indicators of compliance or violation against longer-duration limits. Precise terminology regarding noise limits and measurement methods is essential, with references to ANSI, ASA, and ISO standards recommended.

9. Noise audits

Some communities suggest annual noise audits of data centres to address concerns about potential increases in noise emissions over time. However, ambient noise may also rise over time. Since data centres operate 24/7, isolating their noise emissions from background noise is challenging. Unlike other facilities that can temporarily shut down for assessments, data centres lack this flexibility. Therefore, audit requirements must consider their unique operations and the changing ambient noise conditions.

10. Legal non-conforming uses

The data centre industry has worked with communities to address noise complaints and is open to revising noise ordinances. However, any changes should consider the applicability date for new or stricter requirements on existing facilities that complied in good faith with prior regulations. Existing facilities should receive accommodations, such as exemptions or phased schedules, to avoid penalizing them for adhering to previous standards.

11. Balancing the environment and development

Balancing environmental concerns with the need for data centre developments is essential. Overly restrictive noise ordinances could impede future projects and create inequities by targeting data centres specifically, as they are not uniquely noisy compared to other industries. Any revised noise ordinance should standardize the noise study process, set clear requirements, and establish limits that allow reasonable development while ensuring compatibility with residential and other sensitive land uses.

These considerations serve as a foundation for developing or revising noise ordinances, encouraging stakeholders to review existing regulations against community concerns and industry standards. The goal is to protect community interests while facilitating business operations and development.

Developing new or revised noise ordinances for data centres and industrial facilities requires a comprehensive review of existing standards, technical factors, and stakeholder insights. By addressing key issues such as noise limits and compliance measurement, authorities can create effective regulations that balance environmental and economic concerns.