Managing noise

posted on 21st June 2018

The apparent paradox about airport noise management is that engines are much quieter than they have ever been, yet people are still becoming more sensitive to aircraft noise. 

OLYMPUS DIGITAL CAMERA

Phil Stollery, the product marketing manager for Brüel & Kjær, a company specialising in noise-management technology, believes that there are two reasons for this increasing sensitivity.

“The first is that people are treasuring their e

nvironment more and more, and want respite from all noise,” he says. “They have a heightened perception of noise and we even get complaints about noise from planes at 6,000ft (1,829m). It’s slightly crazy as you can barely hear the engines at that altitude and a car on the road is louder.”

The second reason, according to Stollery, is that there are far more aircraft in the sky than there used to be.

“Aircraft have been getting much quieter, but the noise is far more frequent,” he observes. “It’s not just about the level of decibels. In assessing the impact of noise these days, we talk more about the number of times you might be disturbed in a given location.”

Brüel & Kjær’s Airport Noise and Operations Management System (ANOMS) is in use at around 250 airports worldwide, ranging from large internationals, like London Heathrow, Chicago and Los Angeles, to small regional gateways, such as Eindhoven and Birmingham in the UK.

ANOMS is linked to both radar and as many as 35 noise-tracking monitors deployed around the airport and its environs. The monitors are complex acoustic instruments with microphones, which do all the measurements of noise, then transfer the data over phone lines, or the Internet, to the central computer system.

“We stitch together different sets of data to measure the impact of noise levels on the community,” Stollery informs. “From the noise monitors we understand how noisy something is, and from the radar we understand where it is. Then, from the flight-time data systems, we understand what aircraft is. If a particular aircraft was flying there at such a time, we know that was the source of the noise.”

The ANOMS data is housed in centres away from the airports and can be accessed on the internet. The system monitors every aircraft and builds up a detailed history of when, where and why the airport was noisy. The detailed information helps airports to manage aircraft noise efficiently, he says.

The airports scrutinise the data and work with airlines that have exceeded the permitted decibel levels to improve their performance. It’s common practice for airlines to be fined, especially in the UK, but the money from the fine is usually funnelled back into local community projects.

ANOMS also records information about complaints from the public. It works out which flight made the noise and automatically generates a letter to the complainer laying out the relevant details.

“The letter says ‘we received your complaint. This was the flight which caused the noise and this was the flight path, so can see if it was on, or off track, and determine the reason why it caused a complaint’.

“Such a letter might not make the airport, or aircraft, any quieter but it shows to the complainer that the airport knows what’s going on and that it has it under control. If the noise was excessive, it is dealing with it.”

Stollery believes that airports that communicate openly and address issues with the public are more able to develop ‘Environmental Capacity’, which is simply the capacity to grow within the constraints of local communities.

“Many airports are focused purely on noise reduction, but there’s a second element to building Environmental Capacity which is making communities more tolerant of what’s going on,” he adds.

“You can set the community’s expectations if you tell people when it’s going to be noisy and when it’s not; then they are likely to tolerate it. It’s also about putting the noise in places where people expect it to be and not deviating from that. If you live under a flight path and you know it’s noisy, you can take measures to manage it.”

One of Brüel & Kjær’s most recent developments is its WebTrak tool, which allows communities to go on the internet and track exactly what happened at a specific time.

“You can stick in the time of day on a given date and it will replay the flight track going on around the airport. Let’s say you were woken up last night by aircraft noise, you can type in 10.10pm and see what was happening at that time.

“You can even see the aircraft flying around the outskirts of the airport. You can also type in your address and it will measure in metres how close it came to your house.”

Stollery explains that the transparency of information provided by WebTrak is a great way of developing constructive dialogues with local communities.

“There’s a lower risk of people ringing up and screaming and shouting at the airport because it’s possible to explain to them why the aircraft was flying so much lower than normal. There may have been exceptional circumstances, such as weather conditions or airport maintenance. Then you can say, ‘It will be finished on Tuesday’. You’ve built awareness and understanding with the person complaining,” he says.

Innovation at Vancouver International

Vancouver is one of the major airports that has adopted the WebTrak technology as a means of enhancing its relationship with the local community.

“We’ve had all the data at Vancouver for some time, but we wanted to share it with the community, so we introduced WebTrak,” says Mark Cheng, the gateway’s supervisor noise abatement and air quality. “We’ve had great feedback from local councillors telling us that their constituents love it. It works well because people find it much easier to visualise flight routes.”

Cheng notes that Vancouver was the first Canadian airport to introduce the WebTrak technology as part of its comprehensive environmental management strategy. “We have to manage our noise very carefully because Vancouver is very close to densely populated urban environments and sensitive habitats,” he comments.

Cheng adds that WebTrak was part of the gateway’s broader strategy to involve the local community as much as possible. For example, local community leaders are well represented on the airport’s Noise Management Committee.

“They debate in an open forum alongside our regulator Transport Canada, air traffic control and the airlines. It helps us to balance the views of the community with the views of industry,” he says.

Vancouver was also the first Canadian airport to install a dedicated ground run-up enclosure (GRE) designed to reduce the noise of aircraft carrying out engine maintenance at night.

“They test the engines at full power in the middle of the night for 20-30 minutes at a time. In the past we had open areas to minimise it, but the noise propagated into the community,” Cheng admits.

It took Vancouver three years to complete the project, including finding a suitable location and building the enormous facility, which was opened at the start of this year. Acoustic monitoring of three aircraft in the enclosure revealed major reductions in noise.

“It has far exceeded our expectations. Compared to previous run-up locations, we’ve seen greater than 20 decibels of noise reduction, so it’s four times as quiet. It has reduced noise significantly in the surrounding community and the local citizens are very appreciative of having it in place.”

Blast Deflectors, the Nevada-based company that designed and erected GRE at Vancouver, is at the forefront of noise-reduction technology. The GREs are just one of the company’s noise-combating solutions.

Its jet-blast deflectors protect blast-sensitive areas, such as public roadways, buildings and parked aircraft from high-velocity jet blast. A variety of types are available depending on aircraft type, power settings and the nature of the area. Not all airports require them, but those with jet-blast hazards most certainly do.

Jet-blast deflectors do little to protect communities from noise, however, and if an airport also wants to reduce noise, Blast Deflectors provides more specialised solutions.

“To reduce noise, a jet-blast deflector is incorporated with acoustic panels designed specifically to block the low-frequency sounds generated by aircraft engines,” explains Don Bergin, Blast Deflectors’ director of technical sales.

For such hybrid projects, several factors need to be taken into account. First, the aircraft mix changes the specifications. A widebody aircraft with four engines requires a very different solution from a single-engine piston aircraft. Second, the engine power settings must be studied.

Blast Deflectors has to provide a range of customised solutions for different airports. “If engine tests need to be performed, a ground run-up enclosure may be the solution, such as at Vancouver airport,” Bergin remarks.

“But if high-power aircraft will only be idling, or taxiing, the solution could be a taxi-power blast deflector equipped with acoustic panels. Finally, the proximity of the noise sensitive areas to the aircraft position must be analysed, as this impacts the required configuration and type of deflector/enclosure required.”

Blast Deflectors recently installed a taxi-power jet-blast deflector equipped with acoustic panels at San Diego International airport.  This hybrid jet-blast deflector and acoustic barrier was required to protect a series of apartment buildings adjacent to the airport from the noise generated by parked aircraft running auxiliary power units (APUs).

Another example of a solution adapted to the needs of an individual gateway is the newly constructed GRE at Detroit Metro airport. This facility can accommodate up aircraft as big as a B747-8 and allows Code C aircraft to self-manoeuvre into position without the use of a tug.

Other GRE facilities have been installed in the last 12 months at airports including Zurich International, Detroit Metro and the Spirit of St Louis.

“Each facility had unique features and design requirements, but the driving factors were the same:  The facilities needed to be highly usable regardless of wind conditions and they needed to minimise the acoustic impact of ground run-ups on communities surrounding the airports,” Bergin notes.

GRE development

GRE technology has developed enormously over the past 50 years. The earliest enclosures built in the 1960s consisted of bales of hay stacked high around the engine test area. These were quite effective acoustically, but they were unsightly, highly flammable and lacked durability.

Then, in the 1970s, concrete and simple acoustic panels were shaped into run-up enclosures. But they were only usable when the wind was blowing directly into the facility.

Finally, in the 1990s, the first aerodynamically stable GRE was built at Chicago O’Hare. Because of its unique design features, such as vented side walls and smooth, aerodynamic shapes, this GRE allowed successful ground run-ups in a wide variety of wind conditions. This type of facility has since become the standard for GREs.

Two major changes in the last 20 years have made GREs an increasingly important option for airport planners, Bergin believes.

“First, communities around airports have grown and, in many cases, encroached on airports. As a result, noise has become a major challenge for airports,” he said.

“Secondly, environmental regulations worldwide have become more stringent in the last 20 years. This trend has led to operational limitations on ground run-ups that can only be reduced, or eliminated, by building a GRE. Also, a GRE can be an effective concession to local communities for airport operators to increase overall operations.”

For many years, a GRE was a viable option only for very large, international airports with extensive maintenance operations. But in the last five years, BDI has built GREs for smaller airports, such as the Spirit of St Louis and Bogotá International. It will start construction of a new GRE at Budapest International airport later this year.

“While a GRE continues to be an option for very large airports, smaller airports also require a solution that will reduce the impact of ground run-up noise on nearby neighbourhoods,” Bergin believes. “As a result, BDI has developed a new range of GREs designed specifically for the unique aircraft mix and requirements of smaller airports.”