Two different questions
A peak level describes the loudest point of a particular sound event. An exposure indicator combines sound over time. A daily average therefore cannot tell you the loudest individual flyover or how many separate disturbances a resident noticed. Before comparing numbers, establish the metric, location, time period and whether the value was measured or modelled.
What DNL means in the FAA framework
The FAA uses day-night average sound level (DNL) to express cumulative exposure across 24 hours. Its calculation gives nighttime events an additional 10 dB weighting during 22:00–07:00. That weighting belongs to the metric: it does not mean the aircraft physically becomes 10 dB louder at night. Other jurisdictions may use other periods or indicators.
Avoid averaging decibels like percentages
The decibel scale is logarithmic. A simple arithmetic mean of sound levels is not an energy-average exposure calculation. Traffic count, aircraft mix, routes and the day/night distribution affect the result. A percentage reduction in a manufacturer’s noise footprint also cannot be treated as the same percentage reduction in a sound level at one house.
Questions for an airport noise report
Look for the map’s year, operating assumptions, monitor locations, measurement metric and treatment of night operations. Compare like-for-like contours or monitoring periods. Noise and climate emissions are different impacts; lower fuel burn alone does not establish lower sound exposure for every neighbour.
This publication combines AI-assisted news synthesis and background guides. Sources, announcement dates and material corrections are disclosed. It does not claim a reporting team on the ground.
