By Anil Sood
India’s aviation sector is expanding rapidly. New runways are being added, flight frequency is rising, and airports are operating round the clock. While this growth supports economic development, it also raises a serious public health concern — aircraft noise.
The way we measure that noise matters. At present, assessment largely relies on Leq (Equivalent Continuous Noise Level). Though technical in appearance, Leq alone does not capture the real impact of aircraft noise on people living under flight paths.
What Is Leq — and What Does It Miss?
Leq is an average noise level measured over a fixed period — often 24 hours. It converts fluctuating sound into a single number representing equivalent continuous exposure.
On paper, if Leq remains within prescribed limits, authorities claim compliance.
But aircraft noise is not continuous. It comes in sudden, intense bursts — especially during take-offs and landings. Each aircraft may produce a loud peak lasting less than a minute. If dozens of such events occur throughout the day and night, the average may still appear acceptable.
The problem is simple: averages hide peaks.
Residents do not experience averages. They experience repeated disturbance.
Why Peak and Night Noise Matter
Scientific studies across Europe and North America show that repeated high-intensity noise events:
- Disturb sleep
- Increase stress hormones
- Elevate blood pressure
- Raise long-term cardiovascular risk
- Affect children’s learning and concentration
It is not the “average noise level” that wakes someone at 2 a.m. It is a sudden aircraft overhead.
When regulation depends only on Leq, the most harmful component of aircraft noise — night-time and peak events — gets diluted.
The Global Shift: Lden and Lnight
Many major international airports now use additional indicators such as:
- Lden (Day–Evening–Night Level)
- Lnight (Night-time Noise Level)
Lden applies penalties to evening and night noise, recognizing greater sensitivity during those hours. Lnight focuses exclusively on night exposure to protect sleep.
Airports such as Heathrow (UK), Frankfurt (Germany), Schiphol (Netherlands), Paris Charles de Gaulle (France), Zurich (Switzerland), and Madrid Barajas (Spain) use Lden and Lnight in regulatory frameworks.
These are not symbolic metrics. They are linked to enforcement.
Penalties and Enforcement in Other Jurisdictions
In several European jurisdictions:
- Airports face financial penalties if noise limits under Lden or Lnight are exceeded.
- Aircraft operators may be subject to noise-related charges, where noisier aircraft pay higher landing fees.
- Persistent violations can lead to operating restrictions, slot reductions, or withdrawal of night flight permissions.
- At Frankfurt and Zurich, strict night curfews are enforced.
- In France, the independent authority ACNUSA can impose monetary fines for exceeding permitted noise thresholds.
- Schiphol has faced legally mandated flight caps and operating reductions tied to noise exposure limits.
These measures reflect a clear principle:
Growth must not override public health.
The Indian Context
India now operates multiple high-density airports with round-the-clock activity. In several residential areas, aircraft pass overhead at short intervals — including late at night and early morning.
Yet regulatory assessment continues to rely predominantly on Leq.
This creates a disconnect between reported compliance and lived reality. A 24-hour average may appear within limits even if residents are awakened multiple times each night.
Environmental governance cannot be reduced to mathematical averages.
The Way Forward
Noise monitoring around Indian airports must include:
- Leq (for overall exposure)
- Lden (to reflect evening and night penalties)
- Lnight (to protect sleep)
- Peak event measurements (Lmax) and frequency of exceedances
Only a combined framework provides a truthful picture.
This is not about opposing aviation growth. It is about responsible development. If India aspires to world-class infrastructure, it must adopt world-class environmental standards.
Noise cannot be averaged away.
And its impact on human health cannot be ignored.