Close to home
In addition to laying countless kilometres of cable, a major challenge for operators concerns the construction of the numerous PoP and RAN stations required to connect backbones to various access networks. In densely populated urban areas, the shelters housing these PoP and RAN stations are usually located in the immediate vicinity of residential or mixed use areas. At the same time, the development of new residential areas is leading to stations being built close to buildings in rural locations.
PoP and RAN stations contain sensitive IT and networking components, so a constant internal temperature must be ensured to protect the technology from the elements and maximise uptime. In many cases, this is only possible using mechanical refrigeration. As a result, the noise generated by compressors, pumps and other components should be considered at the planning stage to ensure that the systems comply with all relevant noise protection regulations.
What is sound?
In acoustics, a distinction is made between sound power and sound pressure. Sound power is the total acoustic energy produced by a sound source. Conversely, sound pressure is a location dependent variable and is measured in dB(A) according to the A weighting curve, which is based on the human perception of sound and mimics the ear's response.
If sound pressure increases by 10dB(A), it is perceived by humans as being approximately twice as loud. In terms of measurement technology, however, sound pressure doubles with an increase of just 3dB(A).
Additionally, the sound power of several sound sources can add up to a higher overall sound pressure level. Two identical sound sources lead to an increase of 3dB(A), while four identical sound sources to an increase of 6dB(A). To achieve an increase of 10dB(A), 10 identical sound sources would be required. However, if one sound source is more than 10dB(A) quieter than another, it usually does not lead to a significant increase – the total sound pressure of both sound sources corresponds to the sound pressure of the louder sound source.
The structural relationship between the sound source and the point of sound impact is also relevant. Factors like reflections and absorption by buildings or vegetation can either increase or decrease sound pressure at the impact site, depending on specific local conditions.
How does sound affect people?
Human perception of sound varies widely from person to person, with familiarity playing a crucial role. Sounds that are well-known or expected tend to be perceived as less disruptive than unfamiliar or surprising noises, even when both have the same sound pressure level.
This phenomenon relates to how the brain processes and interprets auditory information. When a sound is familiar, the brain can predict its pattern and duration, reducing the sense of intrusion. In contrast, unexpected sounds trigger heightened alertness, as the brain interprets them as potential threats, leading to increased discomfort or annoyance.
For people who are sensitive to noise, a volume of 25-30dB(A), (the noise level of quiet speech), can be enough to reduce the restfulness of sleep. Continuous noise creates stress and impairs general wellbeing, with 60-65dB(A), (the noise level of shouting), having the potential to cause serious health problems. However, hearing damage usually only occurs at sustained noise levels of at least 85dB(A).
Noise protection regulations
In Europe, noise protection for residential areas is governed by a combination of EU directives and national laws. The Environmental Noise Directive (END) 2002/49/EC serves as a foundational framework, requiring EU member states to assess and manage environmental noise. It mandates the creation of noise maps and action plans for urban areas with populations exceeding 100,000, focusing on long-term noise reduction strategies.
Individual countries have implemented these guidelines through national regulations, often specifying permissible noise levels and setting distinct limits for daytime, evening and nighttime hours to protect residential zones. In the UK, this directive has been transposed into the Environmental Noise (England) Regulations 2006 and its subsequent amendments.
Residential areas are typically classified based on land use and sensitivity to noise. These classifications influence permissible noise limits, with stricter thresholds for quiet zones such as hospitals, schools and purely residential districts, compared to mixed use or commercial areas. Typical daytime limits range between 50-65dB(A), while nighttime limits are more stringent, often between 40-55dB(A).
To calculate noise exposure, standardised approaches like the day-evening-night level (Lden) methodology are used. Lden is a 2002 European standard that addresses factors such as the type of noise source, duration and frequency over the course of an entire day. Legal enforcement involves regular monitoring, public reporting and the ability for residents to seek remediation if noise levels exceed regulatory limits. Local authorities play a significant role in enforcing noise limits and providing guidance on acceptable noise levels to protect public health and wellbeing.
Several standards must also be observed when preparing noise forecasts and carrying out noise measurements. These include ISO 9613-2, which provides a method for predicting the attenuation of sound as it travels outdoors from a noise source to a receiver, while ISO 12354-4 specifies a calculation model to estimate the sound power level radiated by a building's envelope due to airborne sound inside the building. ISO 3746 outlines methods for determining sound power levels of noise sources using sound pressure measurements.
