Nobody likes a noisy neighbour. San Francisco International Airport (SFO) has long consulted with the surrounding community, and works hard to ensure its operations and aircraft noise cause the minimum disruption. It has a range of noise abatement strategies that it constantly monitors to make sure they are working as effectively as possible.

“We feel that noise abatement is the correct thing to do,” says Doug Yakel, SFO’s public information officer. “In 1978, SFO promulgated the airport’s first noise abatement regulation and, in 1983, we published a new, more stringent noise mitigation plan.”

SFO employs two approaches: working with airlines to reduce the noise its aircraft generate and paying for sound insulation in nearby properties. A variety of voluntary noise abatement procedures apply to all airlines, with SFO going to great lengths to cut night-time disturbance.

Restricting operating times would stop nocturnal disruption completely, but SFO cannot mandate this due to potential safety issues and restrictions under the 1990 Airport Noise and Capacity Act. Instead, its Preferential Runway Use and Night-time Noise Reduction programmes have the general aim of keeping aircraft as far away as possible from residential areas at all times.

Take heed

Aircraft are at their noisiest during take-off so, as the quietest departure option, runways 10 and 28, and 01’s water-facing, over-the-bay route are the best choices. In contrast, SFO always discourages straight-out departures on runways 28 L and R, which fly over densely populated communities.

SFO is fortunate to have half of its runway ends over water. That means the majority of our close-in operations occur over water, alleviating the greatest noise burden for many.

“SFO is fortunate to have half of its runway ends over water,” says Yakel. “That means the majority of our close-in operations occur over water, alleviating the greatest noise burden for many.”

To keep aircraft away from residents, SFO’s ‘Gap’ procedures also ask aircraft leaving via runways 28 L and R to climb while still directly over the airport itself. This allows a reduced-power climb-out over the communities to the west.

Aircraft on runways 28 L and R departing to the north and east make the required right turn close to the airport, over an industrial area, rather than further out over residential communities. Aircraft arriving on these runways are asked to use approaches that are offset rather than straight in, thus remaining over the water for as long as possible.

Then there are ‘oceanic tailored arrivals’. In these, rather than flying a ‘staircase’ series of level segments, a gradual automated descent starts several hundred miles off the coast of California to reduce noise and fuel consumption.

Where the optimum option isn’t available, SFO works with FAA air traffic controllers to offer alternative or modified procedures that still minimise disturbance. The airport also asks pilots to follow Noise Abatement Departure Procedure NADP-1, which keeps engine thrust – and so the ensuing noise – as low as possible.

Yakel emphasises that all the routings are voluntary. “These procedures are not always possible due to the weight of the aircraft and requirements for take-off distance,” he says. “The pilot in command of a flight always has the final decision on runway use.”

On the ground, SFO restricts engine run-ups and auxiliary power unit use, backed by cameras, noise monitors and airfield safety officers. But with no way to properly punish poorly performing airlines, SFO relies on its Fly Quiet programme and awards to raise awareness, as well as providing feedback to airlines and pilots.

Fly Quiet produces a rating for each airline in six performance areas and also notifies airlines if they exceed noise limits. Scoring highly means scheduling newer, quieter aircraft models, as well as sticking to preferred arrival and departure procedures. Scheduling flights outside the more stringent night-time noise limits also helps, as does flying higher along departure routes.

“Sanctions have been blocked by legal decision at the federal level,” says Yankel. “By working directly with the airlines and FAA, we have been successful in modifying behaviour on certain procedures. Fly Quiet is a definite success.”

Challenge 21

A vital boundary in minimising and monitoring noise impact is something called the State Community Noise Equivalent Level (CNEL) 65dB noise contour line. First generated in 1983, it defines the area within which the State of California requires the airport to establish a noise monitoring plan and report quarterly on it. CNEL is very similar to the Day Night Level (DNL) noise metric used elsewhere in the US and in many other countries too.

SFO uses its Aviation Environmental Design Tool application to generate CNEL values for the airport and surrounding area. That involves annually processing all flight data: runways, specific aircraft types, date and time of flights, distance flown and routes. Just like a conventional map joins points of equal height to form contours, so connecting 65dB noise values produces the noise contour that surrounds the airport.

Between 10pm and 7am, an extra 10.00dB penalty is added to the calculated noise level. Unlike the DNL, California’s CNEL also adds a 4.77dB penalty between these hours.

However, the best way to avoid disturbance is to encourage people not to live near a busy airport. California’s Title 21 regulation requires SFO to “mitigate” all incompatible land uses within the 65dB contour. These uses include homes, schools and hospitals. SFO works hard to influence local planners not to locate there, but the booming local economy makes it hard to discourage residential development.

“The SFO Planning Department works very closely with the planning departments in the surrounding jurisdictions,” says Yakel. “There are times where the state’s zoning density requests of the local cities come into conflict with the airport’s preferences.”

Title 21 also requires SFO to produce a Noise Variance Action Plan to reduce incompatible land uses within a certain time frame or otherwise reduce noise levels within the closest properties. Here, SFO deploys its long-running Residential Sound Insulation Programme (RSIP). An extensive and ambitious programme, RSIP has an annual budget of $1.1 million over the next five years. FAA grants cover up to 80% of the costs within the 65dB contour, though SFO itself funds insulation for many properties that fall just outside the boundary.

“The owners have received acoustic treatment at no cost to them,” says Yakel. “The resulting reduction in interior noise level has improved their quality of life, and the properties have appreciated in value.”

RSIP has been extremely successful, reducing the impact of aircraft noise in more than 15,000 properties. SFO was the first Californian airport to become variance-free under Title 21, meeting all federal and state noise insulation requirements by the mid-2000s.

However, the RSIP programme continues to support residents in the small remaining number of properties that, for whatever reason, had previously missed out on the insulation offered. “About 50–60 of these properties located inside the updated noise exposure map may be considered for insulation in the next five years,” says Yakel.

The owners have received acoustic treatment at no cost to them. The resulting reduction in interior noise level has improved their quality of life, and the properties have appreciated in value.

Good walls make good neighbours

SFO’s Aircraft Noise Abatement Office (ANAO) is the management hub for RSIP, Fly Quiet and all other noise abatement initiatives. Launched in the early ’70s, it designated the first 12 noise monitoring sites in 1975.

With growing airport traffic, pressure from the local community for action had been growing for some years prior, with litigation arising from some individuals. Community liaison and consultation by ANOA remains critical in building trust with residents.

“There was a belief that their voices were going unheard,” says Yakel. “ANAO aims to efficiently and accurately provide an avenue for people to be heard, and gain knowledge and information in a friendly and transparent manner.”

The SFO/Community Roundtable, with its various subcommittees and technical working groups, is a key forum for this information exchange. ANAO officials also attend community events to spread the word about aircraft noise abatement. Online channels have also proved immensely popular, with the airport having made live flight radar tracks available in 3D via the web since 2001; this system, VOLANS, has drastically cut the volume of phone and email complaints. “People are smart and would rather get a quick answer for themselves than call someone,” says Yakel.

Today, ANAO has a sophisticated monitoring operation employing the Brüel & Kjær Airport Noise and Operations Monitoring System. Installed in two phases and completed in 2008, it cost just under $3 million.

The highly automated system takes in complaint data from online forms, emails and the telephone hotline, and then correlates it with flight tracks and noise monitoring data to produce a range of automated reports, analyses and alerts. Linked to it are 29 fixed and four portable noise monitoring sites, along with three fixed and one mobile ground run-up monitors.

“It’s taken SFO back to the forefront of aircraft noise monitoring,” says Yakel. “The greatest single assist was the complete system integration. Before that, we had many stand-alone systems that had to be manually correlated and tied together for reporting and data visualisation.”

SFO’s noise abatement story is one of steady improvement, with much quieter modern aircraft helping progress greatly – but until aircraft are completely silent or take off vertically over the airport, ANAO will still have much to do.

“Over the years, we have learned that an open-door policy is the best. Working together is often cathartic, and many [residents] have gone from very distrusting to agreeing with the SFO ANAO. I have learned that noise abatement is not revolutionary but evolutionary,” concludes Yakel.