Ordering the government to “take all mitigating measures for reducing noise pollution…expeditiously”, India’s environment tribunal, the National Green Tribunal (NGT), has recently directed the Airports Authority of India (AAI) and the Delhi International Airport Limited (DIAL) to implement measures authorized by it in a 2017 decision. The order aims to curb noise pollution in India’s capital New Delhi.

According to the order, the measures include “construction of sound barriers” around the airport. The government has also been directed to provide “a green belt around the boundary wall of the airport while keeping the safety and security both in mind. The plantations shall be of the species that would only grow to the permissible height or would be maintained at the permissible height only.”

Relevant authorities such as the AAI are to issue instructions to airlines “whose aircraft land at the runway of the IGI airport to ensure judgment-based use of reverse thrust keeping in view weather, length of the runway, wind, and other attendant circumstances to reduce the noise level particularly at the time of landing of aircraft.”

The measures are not limited to structures around the airport or the aircraft. Public transport used at the airport is also expected to adhere to environmental norms. The order also instructs that “all the coaches/buses and other vehicles plying at the airport should be Compressed Natural Gas (CNG) and must comply with the prescribed emission standards. Non-CNG buses/coaches or other vehicles plying at the airport should be converted to CNG”.

Aircraft noise pollution is a harmful noise effect produced by any aircraft or its components during the various phases of a flight. Health consequences include sleep disturbance, hearing impairment and heart disease, as well as workplace accidents caused by stress. Memory and recall can also be affected. Governments have enacted extensive controls that apply to aircraft designers, manufacturers, and operators, resulting in improved procedures and cuts in pollution.

The Air Transport Action Group (ATAG) points out that the industry has been working to reduce noise for decades. On average, aircraft are already 50% quieter today than they were 10 years ago, and 75% quieter than the first generation of jet aircraft. It is estimated that the noise footprint of each new generation of aircraft is at least 15% lower than that of the aircraft it replaces. In 2013, the International Civil Aviation Organization (ICAO), the United Nations’ intergovernmental body on aviation, introduced a new noise certification standard. The requirement is that new aircraft types are least seven decibels quieter than those built to earlier standards. The purpose of these aircraft noise standards is to ensure that the best noise technology continues to be used on future aircraft types.

The certification was one in a series of measures to reduce jet engine noise. In fact, the ICAO estimates that between 1998 and 2004, the number of people exposed to aircraft noise around the world was reduced by 35%.

According to ATAG, from looking at such factors as the proportion of air travelling through the engines, the size of the fan blades in the engine, the position of the engine on the aircraft body and even the size and number of flaps that help control the wing shape, research and development on noise has been extensive. The latest large aircraft, the Boeing 787 and Airbus A380 have noise ‘footprints’ that are remarkably small.

The industry is working hard to make aircraft a further 50% quieter by 2020. There is a powerful incentive to continue tackling this issue, as concerns over noise pollution can – and do – affect the viability and acceptability of airport expansion plans.

Controlling where the planes fly when departing and approaching airports has an important impact on noise exposure. The placement and use of runways is fundamental and preferred runway use can, for example, try to maximize night-time approach and departure tracks over a sea or lake where the noise impact is minimal.

In parallel with aircraft noise minimization through technology and air traffic management, ATAG data reveal that land-use planning is a crucial process for minimizing the number of people exposed to high levels of aircraft noise.  Airports need to work with local authorities to put in place zoning rules in areas impacted by high levels of aircraft noise.  Effective land-use planning can discourage or prevent inappropriate new residential, health or educational developments, and encourage light industry or storage areas not sensitive to aircraft noise.  In some areas, sound insulation and ventilation can be required for new or existing dwelling to at least improve the indoor noise levels.