Noise

Aviation operations inevitably involve a degree of noise for neighbouring communities, especially at the Zurich site. The Zurich Airport Group is aware of this and employs numerous measures to minimise adverse impacts.

Relevance

Noise is less of an issue for the companyʼs majority-owned subsidiaries in Brazil and Chile where the volume of air traffic is much lower. In the case of Brazil, the number of flight movements at all sites is below the threshold as of which the government demands that noise be monitored. Moreover, most take-offs and landings in Brazil are over the sea, while the airports in Chile are sited well away from large conurbations.

Approach and progress

Zurich Airport Ltd. employs technical, structural, operational and financial measures to tackle aircraft noise, all of which are aimed at reducing noise at source and along propagation pathways. At Zurich Airport it seeks to ensure that noise does not exceed the emission limits in any residential areas outside the zone defined in the Sectoral Aviation Infrastructure Plan (SAIP). In contrast to 2021 this target was not met in 2022 (figures for the reporting year are not yet available, see Noise statistics). The reasons are explained in the following section “Night flights and special authorisations”.  In addition, the Zurich Airport sound insulation programme includes various passive noise mitigation measures which Zurich Airport Ltd., as the originator of the noise, is obliged to put in place. These include in particular the installation of sound-insulating windows in living rooms and bedrooms. The company is aiming to install sound-insulating windows in at least 200 further properties a year between 2022 and 2026, or alternatively to reimburse homeowners. As in recent years, this target was also met in 2023.

Communication with local residents

Zurich Airport Ltd. is aware that aviation noise can be perceived as a nuisance and that the public has a need for information. Transparent information and dialogue with residents are vital. The company has therefore reported on the measures it has taken and provided updates on noise statistics and flight operations for many years already. For instance, the number of take-offs and landings at the Zurich site, broken down by runways and flight paths, is reported on the companyʼs website each day. Residents affected by aircraft noise can call or use an online form to contact Zurich Airport Ltd. directly with any queries or concerns, and staff from the Noise Management department will respond to specific questions.

Besides individuals, a number of bodies including municipalities in the airport vicinity, the Canton of Zurich and other neighbouring cantons, districts across the border in Germany and a variety of agencies and citizens organisations concerned with air traffic noise make representations to Zurich Airport. The company maintains a regular dialogue with these groups too. Exchanges are more frequent ahead of changes to take-off and landing operations.

In the reporting year, the number of enquiries and complaints declined by just under 20% compared to the previous year. The most frequent reason for enquiries and complaints concerned the inbound flights from the south in the evening hours and regular aircraft delays after 11 p.m. (see Noise statistics).

Noise exposure is less of an issue in Brazil and Chile. Nevertheless, complaint channels are provided at each of the airports in Florianópolis, Vitória and Macaé, available for noise information and complaints. The environmental licences of these airports are subject to the obligation to set up an easily accessible digital hotline for noise complaints and to submit quarterly reports to the authorities. See the Business ethics section for more information.

Noise monitoring

In order to objectively assess the noise situation and levy noise-related charges, it is necessary to have accurate measurements of noise levels. Data on air traffic noise in the vicinity of Zurich Airport have been collected since 1966. A network of noise monitoring stations currently at 14 fixed locations near arrival and departure routes is operated. The system automatically links the noise data recorded by these monitoring stations to the corresponding flight movements. These data are published monthly in a noise report that can be freely accessed on the companyʼs website. As prescribed by the Sectoral Aviation Infrastructure Plan (SAIP), aircraft noise exposure and the progress of mitigation measures are analysed in a comprehensive report each year which is submitted to the Federal Office of Civil Aviation (FOCA). This report is then used as the basis for taking corrective action (see Night flights and special authorisations).

Following the recovery of air travel, which had almost come to a complete standstill in 2020 due to the Covid-19 pandemic, the number of take-offs and landings increased during the reporting year compared with the previous year. The volume of air traffic had almost reached pre-pandemic levels again by the end of 2023. Accordingly, an equivalent or higher level of aircraft noise than in the previous year was recorded during daytime hours at the four main monitoring stations. However, the figures did not reach the 2019 level at all monitoring stations.

The diagram above shows changes in exposure to aircraft noise at Zurich Airport over time. It shows the noise contour emission limits for residential zones for various years. Comparing the noise contours from different years shows the reduction in noise exposure despite a steady rate or increasing amounts of air traffic. This can be attributed to technical advances in aircraft design resulting in lower noise emissions. The sole exception is 2022, in which the reduction in noise was due to fewer flight movements. The current noise contours for the reporting year will only be available at mid-year. 

Flight path monitoring

Take-off routes from Zurich Airport were configured to avoid low overflights of densely populated areas wherever possible. The Noise Management unit monitors all aircraft departing Zurich Airport for adherence to the prescribed flight paths. These are mandatory during daytime at least up to an altitude of 5,000 feet (approximately 1,500 m above sea level) and at night up to flight level 80 (approximately 8,000 feet or 2,500 m above sea level. Compliance with these noise-optimised flight paths is monitored with the aid of the Airport Track And Noise Monitoring System (ATANOMS).

An aircraft may only deviate from the prescribed flight path if there is good reason to do so, for instance to avoid storm clouds or following instructions from an air traffic controller. If there is no legitimate reason, an investigation is triggered, and the pilot in question will be asked to submit a statement in writing. These investigations often also involve interviews with representatives of the airlines. If the investigators are not satisfied, the matter may be referred to FOCA. This constant monitoring encourages the airlines to optimise the take-off phase at all times.

As in the previous year, the most frequent reason for deviations from the prescribed flight paths were specific instructions from air traffic control. 132 (2022: 138) investigations into unjustified deviations were launched and 38 (2022: 39) interviews with chief pilots were conducted.

Night flights and special authorisations

Residents living near Zurich Airport perceive night-time flights to be particularly intrusive. Complaints are often received about flights after 11 p.m. Together with its partner companies, Zurich Airport Ltd. has taken steps to reduce the number of flights after 11 p.m. It is not yet possible to implement the key measures that would bring about a lasting improvement, such as better separation of take-off and approach routes, or extending the two shorter runways. Given the lengthy decision and approval processes involved, this could take several more years. Short to medium-term measures include planning for and providing sufficient personnel and optimising operational processes.

In 2023, 13,564 flights (2022: 10,109) were at night (10 p.m. to 6 a.m.). Special authorisations were issued for a total of 310 flights (2022: 241 flights) during the night-time curfew period (11.30 p.m. to 6 a.m.). Such night flights are only authorised when there are justifiable grounds (see Noise statistics). The many night-time flights were due in particular to the unsatisfactory delays at many European locations, a result of staff shortages. After the pandemic, it was not possible to build up ground handling, security and air traffic control staff numbers in time.

Use of the noise protection hangar

The soundproofed hangar built at Zurich Airport in 2014 greatly helps to reduce the noise from engine ground testing. Engines from aircraft up to the size of a Boeing 747-8 can be tested in the hangar. In contrast to the previous year, when the hangar was out of action for months, in the reporting year all engine tests – with just a few exceptions – were carried out inside the hangar. Although it significantly reduces noise exposure for nearby residents, the hangar does not completely eliminate the noise so there are set limits for the number of tests that may be run.

The majority of engine tests carried out at night were for short-haul and medium-haul aircraft (80%  of all night-time engine tests). Most engine tests for long-haul aircraft such as the A340, A330 and B777 and all other aircraft types were performed during the day. The permitted noise level was exceeded in two individual time slots in 2023. This is significantly fewer than the maximum of 25 instances per year permitted by the operating regulations. According to figures provided by the aircraft maintenance companies, 757 idle tests were performed on the apron and on the stands. 313 of these were run at night (between 10 p.m. and 6 a.m.).

Noise charges and Airport Zurich Noise Fund

Levying noise-related charges gives airlines a financial incentive to operate the quietest possible aircraft on their Zurich routes. All jet aircraft are assigned to one of five noise categories, each of which has a different charge rate based on the time of take-off and landing. In addition, shoulder and night surcharges are applied to flights between 9 p.m. and 7 a.m. These may vary according to noise category and the specific take-off or landing time.

Until the end of 2020, all income from noise charges was credited to the Airport Zurich Noise Fund (AZNF). AZNF funds are used primarily to cover the costs of noise mitigation measures, in particular the sound insulation programme, the south-side sound insulation concept, and the costs of meeting compensation claims for noise and overflying. As the law currently stands, the AZNF has sufficient assets to cover the known future costs for these purposes. Since then, therefore, revenue from aircraft noise charges has been reallocated to the “Aviation” segment. Further details about AZNF can be found in note 20, Airport Zurich Noise Fund.

A total of CHF 15.4 million in revenue was generated from aircraft noise charges in 2023. Of this, CHF 6.2 million were from standard charges applicable to all 24 hours, and CHF 9.2 million were from surcharges levied during shoulder periods and at night. The surcharges were last adjusted in 2019.

Sound insulation

As the airportʼs operator, Zurich Airport Ltd. is obliged to pay the costs of sound insulation measures in properties in the communities around Zurich Airport that are exposed to excessive aircraft noise. As its main measure, the company plans to install sound-insulating windows in at least 200 properties a year between 2022 and 2026, or alternatively to reimburse homeowners. In the year under review, this target was met with 205 properties (properties with their own house number).

In addition, in areas where night-time noise exposure limits are exceeded, the company is offering owners the option of installing automatic window-closing systems or sound-absorbing ventilators. Owners of properties with bedrooms which are located within a clearly defined perimeter, and which were not subject to any obligation to install sound insulation during construction or conversion, are eligible to benefit from these passive noise mitigation measures. Property owners who have already taken the initiative of fitting sound-insulating windows themselves are reimbursed by Zurich Airport Ltd.

As part of phase 1 of the south-side sound insulation concept which was completed earlier, around 1,100 window-closing systems and 900 sound-absorbing ventilators were installed in bedrooms between 2016 and 2018. The total costs amounted to around CHF 3 million.

Noise compensation (formal expropriations)

As air traffic noise can affect the value of a property, the company is faced with around 20,100 claims for compensation from property owners around Zurich Airport. The compensation claims were submitted at the time the airport was privatised and following the imposition by Germany of restrictions on flight approaches over its territory. Any new claims may now only be submitted if there are substantial changes to flight operations; as a result no further claims have been submitted to Zurich Airport Ltd. since then. Of the compensation claims received, as at the end of 2023 over 15,002 (75%) had been concluded, with CHF 87.8 million being paid in noise compensation. All noise compensation claims are paid from the Airport Zurich Noise Fund (AZNF).

As there are very few provisions regarding noise compensation or direct overflights in federal legislation, every open question of law must first be tested in the relevant courts. Legal test cases are being conducted in the interests of processing outstanding claims efficiently. They are helpful both for clarifying questions of law and for obtaining legal rulings regarding the specific situation in the various airport regions.

Noise statistics for Zurich Airport