Airports are often surrounded by the communities they serve. An airport that used to be far away from homes thirty years ago now has neighbors. Great examples (Heathrow and Gatwick) exist in London. LAX is also surrounded by homes.
Airports take noise very seriously. LAX has a real-time online system that enables you to monitor flights. Once the site loaded, on the left click on noise and watch the monitors measure the noise of aircraft movements. Its fascinating to watch. Heathrow also has one of these.
Noise is measured decibels. The decibel range goes from 0 – 140 in intensity, with one decibel being the normal threshold of hearing for most people and 140 being the point where noise causes acute pain. A noise source typically doubles in volume with every 6 – 8 decibel increase and is halved when reduced by the same decibel amount. It is a logarithmic scale.
Take a look at this table that provides a good set of examples of noise.
Noise is a problem. Take a look at this link to get an idea of how much noise is bearable and safe.
Not all aircraft noise is the same. According to the US FAA A-weighted 14 CFR Part 36 at take-off, a Cessna 207 generates 74.3 dBA compared to a Boeing 737-700 which generates 71.8 dBA. This makes the Cessna 20% noisier than the Boeing. The Bombardier Q400 with 75 passengers at take-off makes the same level of noise (61
dBA) as a Cessna 172 seating four.
Airports pay special attention to aircraft noise footprints. Take a look at this 2006 comparison chart for Chicago’s O’Hare. In this 2010 report on Heathrow, the following table illustrates just how crucial noise contours are. Airport noise impact spreads quickly..
The US FAA determined that 65 dBA is the Federal significance threshold for aircraft noise exposure. When looking at noise contours then, this is the line to watch for. Here is the LAX 2Q11 contour map for the airport’s traffic. As you can see there is a long tail footprint going inland over residential areas. The 65 dBA line is clearly marked.
The next generation of aircraft (Airbus’ neo, Boeing’s MAX and Bombardier’s CSeries) are expected to be much quieter than what we experience today. The CFM LEAP and P&W GTF engines are both expected to be significantly quieter. CFM states noise will be cut by half. Pratt & Whitney state their engine will have a 75% smaller noise footprint.
These new technology engines are a crucial step in the right direction for airlines, airports and the communities they serve.
The Pratt & Whitney GTF engine is the most desirable technology there is because it is inherently quiet by virtue of its slow operational fan speed. The GTF concept was created mainly to improve engine efficiency. The noise reduction came as a bonus.
It is the opposite situation for the “next generation” UnDucted Fan or Prop-fan engines: more efficient, but also inherently more noisy.
The engine of the future will have to be leaner, cleaner and quieter. All three parameters will be required and no compromise will be accepted in any of these three areas. Of course safety, reliability and durability will also have to be of the highest standards that current technology will allow.