Outlook: What comes after the quality of life study?
The NORAH Quality of Life found answers to many questions in noise impact research. The answers, however, have only thrown up new questions – as is often the case in science. Answering these new questions will be the job of future studies.
Different measures for the assessment of noise in the future?
The physical measure which the scientists used in the Quality of Life Study is the continuous sound level. Most of the previous noise impact studies also used this measure. The results of the NORAH Study, however, suggest that the continuous sound level alone may not be sufficient to describe all facets of the noise exposure that are relevant for the noise-related annoyance. The reason: air traffic noise has changed dramatically in recent years. Aircraft have become quieter, but there are much more of them in the air than, for example, in the 1990s.
The continuous sound level is a kind of average of all long and short, loud and quiet noise events within a certain period. It does not, however, take into consideration other properties of noise. This is why at one place the road traffic noise can reach a 24-hour continuous sound level of 50 decibels and at another place there can be an air traffic noise continuous sound level of the same strength, and still the noise background is completely different to the human ear. As the annoyance of people over the course of years has increasingly less to do with the continuous sound level, future studies should examine whether it makes sense to take other physical factors into consideration, for example the maximum noise level of the number of flight movements, in order to investigate the effect of noise on humans.
How much annoyance will noise cause in the future?
The Quality of Life Study established that the annoyance due to air traffic noise in the Rhine-Main region rose substantially between 2005 and 2013. It is not possible, however, to predict any future trend from this, in particular as it is not clear what caused this sharp increase. This is why the authors of the NORAH Study recommend that regular investigations are carried out – e.g. every three years – on how the annoyance trend is developing.