Hourly noise at each airport's loudest neighbourhood

Today we’re changing what the peak-hour figures on airport pages mean. The “Peak hour” entry in the key facts row, and the busiest-hour and loudest-hour cards in the statistics section, now show a real hourly noise level at one fixed point near each airport: its loudest residential area.

What the new number is

Each airport page already names its loudest area, the residential spot near the airport where our model puts the highest noise exposure. On the Sydney page that’s Sydenham. At Chicago O’Hare it’s Schiller Park, and at Washington Reagan it’s Rosslyn.

For that point we now work out the noise level for each hour of the day, as a time-weighted average. It takes the sound of every flight that passes in the hour, adds it up, and spreads it across the full 60 minutes, quiet gaps included. That’s the standard way to describe how noisy an hour is. It means one loud flight in an otherwise quiet hour can score lower than a steady stream of slightly quieter ones. Doubling the number of flights raises the level by about 3 dB.

The new figure replaces the earlier peak-hour figure, and it varies from airport to airport and from hour to hour, so it says much more about what you’d hear at home.

Where to find it on an airport page

The key facts row at the top of each airport page shows the peak hour and its level. Further down, the busiest-hour card gives the level at the busiest hour and names the area it applies to. Where we have a full set of hourly levels, a loudest-hour card shows the hour with the highest level.

The hourly chart shows flights by hour of the day. Hover over or tap a bar and the tooltip now gives that hour’s level at the loudest area as a second line.

The chart used to have a switch between flights and noise. We’ve removed it. When we compared the two views across several airports, the noise view mostly followed the flight counts on a compressed scale, so it added a second chart without adding much information. The level you need is now in the tooltip.

Busiest hour versus loudest hour

At most busy airports the loudest hour is the busiest hour, or very close to it, because the hourly level depends so much on how many flights there are. When two hours are nearly tied, we show the busiest one, since a gap that small is within the uncertainty of the estimate.

The exceptions are interesting. In our testing Sydney stood out: at Sydenham, late-morning hours with more heavy jets came out louder than the busiest hour of the day. Small general-aviation airports can also swing a lot from hour to hour on just a few flights.

A few things to keep in mind

The hourly level is a modelled estimate, worked out from recorded flight tracks, aircraft types and distances. It isn’t a microphone reading. It describes one point, the loudest residential area, so most homes near the airport will hear less. For your own street, drop a pin on the airport’s map and look at the hourly breakdown in the pin report.

The new figures appear airport by airport over the next few hours as each one’s statistics are refreshed. Until an airport is updated, its cards show a dash in place of the level.