The study comprises two surveys of the population carried out between 2001 and 2003 and a field study examining the physiological effects of air traffic noise (1). The surveys were conducted by Katja Wirth, Mark Brink ran the field studies and the team was headed by Christoph Schierz. All three are from the former ETH Institute of Work and Organisational Psychology.

The study’s aim was to determine the influence of air traffic noise on the everyday rhythms of the local population. One focus of the researchers was routines during the day, which are disturbed far less by air traffic noise than are activities in the peripheral hours of early morning or late evening. People were also questioned on their feelings towards night-time noise. The questionnaire was sent to around 3,000 people living within 20 kilometres of Zurich Airport, and in 2003 an additional telephone survey followed. 50 percent of those contacted participated in the survey: a satisfactory number, according to the project leader. The study concluded that the suffering generated by noise has a daily rhythm: it is very strong in the morning and the evening, with a few blips over midday. The rhythm of suffering perceived, however, is only conditionally linked to actual levels of air traffic noise.

Stronger reactions from the inexperienced

So-called “moderator variables” played a far greater role, the study found. Examples include a major change in flight schedules, a negative attitude to planes or general dissatisfaction with living location. It is especially interesting that the more the strategies developed to combat noise pollution (for example the use of ear-plugs or membership in an anti-air traffic noise group), the higher the level of resentment. It is also seen that countermeasures are not taken until the level of suffering becomes intolerable. The correlation here is unclear.

Reaction to noise pollution varies from person to person and depends on an individual's "noise history". Here we must differentiate between two situations. People who live in an environment of quasi-stationary noise, i.e. who have lived for over a year with an unchanged level of air traffic noise, are more disturbed by noise the louder it becomes. This means that there is a direct correlation between burden and annoyance. The situation is different, according to Katja Wirth, if considerable change occurs in the noise situation, as it has since 2001 with flights from the east, and since 2003 with flights from the south. This results in a “surplus reaction” of people unaccustomed to airport noise, where according to survey results there was no longer the same link between burden and annoyance. This means that other factors are involved: the level of trust in public authorities, for instance, greatly influenced the perceived level of annoyance.

The daily rhythm of perceived annoyance with air traffic noise is only conditionally linked to its actual level.

Morning noise disturbs more

The main focus of the study was how strongly the population suffers from air traffic noise in the peripheral hours, and how this disturbs sleeping patterns. As over 80 per cent of the population generally went to bed before the last evening flights (midnight at the time of the study) and got up after the flightless night-time hours ended (6.00 am), it is in the peripheral hours that their sleep quality is disrupted. The roughly 60 volunteers who participated in the field study were subjected to simulated air traffic noise of varying intensity and frequency during peripheral hours for a period of 30 days. Using sensors fixed underneath the volunteers’ beds, researchers recorded their movements and pulse rates. Sleep disruption occurred more often in morning hours than evening hours.

It also transpired that a reduction in the number of morning flights would not necessarily lead to an improvement in sleep quality, because it was the first flight that caused the strongest reaction. The level of disruption falls with every subsequent flight. An effective measure to combat sleep disturbances would therefore be an extension of the night-time ban, according to Mark Brink.

To obtain data for comparison, the volunteers were also subjected to street traffic noise on certain nights during the field study. The results give no indication that airplane noise is more disrupting than street noise. The latter was in fact a greater annoyance, but caused hardly any physiological reactions.

No research mandate

96 percent of the study, which cost CHF 420,000, was financed by BUWAL, BAG and Unique Flughafen Zürich AG. It was important to the scientists to take a neutral, scientific position, which is why the study did not ensue from a research mandate but was an initiative of their own.