🔊 Can You Hear Fairness? How Noise Metrics Like N65 Reveal What Communities Really Experience
When it comes to aircraft noise, averages don’t tell the full story. People don’t perceive noise events as an average noise level!
That’s one of the most important insights from our recent study with Manchester Metropolitan University for London Gatwick Airport. Traditional metrics like Leq (which calculates average noise levels) often fail to capture how people actually experience noise – especially in communities near airports. Change is key.
To address this, we explored a more intuitive alternative: the N65 metric and its changes. (Note that other N metrics also may also have merit).
🎯 What is N65?
N65 counts the number of noise events above 65 decibels at a given location. Why does this matter?
Because it reflects the frequency of interruptions – those distinct moments when an aircraft disrupts a conversation, a child’s sleep, or a moment of calm.
This shift from averages to event-based metrics and changes in these metrics has profound implications for the perception of relative fairness in airspace design.
👂 Noise People Feel, Not Just Measure
In our community focus groups, participants immediately grasped the N65 concept. It aligned with their lived experience far better than Leq ever could.
With N65, we could:
- Map where people would hear more or fewer noise events,
- Show how noise burdens shift with each airspace design option,
- Quantify those shifts using the Person Events Index (PEI)—a powerful tool combining population data with noise events to assess overall noise load.
🧠 Fairness Is Transparent – and Understandable
This approach isn’t just technical. It’s about human perception.
When people can clearly see and understand what’s changing – and why – they’re more likely to engage in meaningful dialogue. This is informational fairness in practice, and it’s essential for understanding the relative risk of social unacceptability of different airspace design options.
✈️ Why This Matters for the Future
As CAP1616 guides the next wave of airspace change, we believe N65 and PEI should play a complimentary role. Not to replace policy – but to enhance it with transparency, empathy, and real-world relevance.
👉 Access the full report (CAP2971) and our slides on the Resource page to learn more about how noise data can support better, fairer decisions.
Let’s move beyond averages – and toward metrics that reflect what communities actually experience.
What might make noise data easier for your (or a) community to engage with?
Answer Options:
A. Plain-language explanations
B. Interactive tools like virtual maps
C. Fewer technical terms and more real-life examples
D. Regular updates on how things are changing
Email your answer to: [email protected]
