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|Year : 2002 | Volume
| Issue : 15 | Page : 61--64
The need for a specific noise measurement for population exposed to aircraft noise during night-time
CEPA-CNRS, Strasbourg, France
Director, CNRS-CEPA, 21, rue Becquerel, 67087, Strasbourg cedex
Most of subjective complaints about aircraft noise during night-time refers to sleep disruption. In order to protect populations who live around airports, it is of major importance to define levels of noise considered to be unacceptable during that particular time of the 24-hour period. In addition to an integrated indicator which describes the global noise exposure (Lden), the French authority on airport noise control (Autorite de Controle des Nuisances Sonores Aeroportuaires: ACNUSA) is considering the possibility of defining a maximum noise level [LAmax (1s)] that should not be exceeded at night (from 22.00 to 06.00) by any flying aircraft over residential areas. The main benefit of this single event indicator would be the identification of contravening vessels and application of possible penalty. It is believed that this type of sanction would help protecting sleep in highly noise-exposed areas.
|How to cite this article:|
Muzet A. The need for a specific noise measurement for population exposed to aircraft noise during night-time.Noise Health 2002;4:61-64
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Muzet A. The need for a specific noise measurement for population exposed to aircraft noise during night-time. Noise Health [serial online] 2002 [cited 2020 Apr 6 ];4:61-64
Available from: http://www.noiseandhealth.org/text.asp?2002/4/15/61/31787
Aircraft noise and its impact on exposed population
Aircraft noise constitutes one of the major noise sources to which large areas and numerically important populations are exposed to. Several surveys have been made during the last decades about this specific type of noise exposure (Berglund et al. 1990, DORA 1980, Jenkins et al. 1981, Knipschild 1977, Ollerhead et al. 1992, Tarnopolsky 1978, Taylor et al. 1981, Thomson and Fidell 1990).
The reduction of noise at the source is a necessity for the development of air traffic. The integration of new technologies in conception of modern engines has induce, en thirty years, a reduction of about 20 dB in the average for jet aircrafts. New progresses should still be obtained in two domains: reduction of engine noise and of aerodynamic noise.
In order to reduce the impact of noise from flying vessels, operational rules have also been set by the authority of several airports. Thus, in the approach or taking off phases there could be restricted use for certain trajectories controlled by radar traces. It seems obvious that the use of radar detection combined with noise level measurement will be the main tool to control respect of flying procedures and to decide about possible penalties.
Environmental noise has several effects on humans. The most important effect, in terms of the number of affected people, is so-called annoyance, as determined by means of field surveys. Annoyance is also connected with specific effects such as sleep disturbance, interference with people communication and listening to the audio media. In addition but not always clearly linked, there is a number of serious medical effects as high blood pressure, stress, and cardiovascular diseases. Hearing damage concerns only a small part of the population and is more specifically found in noisy work place and in unconditional listening to loud music. Furthermore, there are negative effects of ambient noise on the learning capabilities of children.
According to an recent European document (1), it seems evident that people reporting noise induced annoyance experience a reduced quality of life and this appears to be a reality for at least 25% of the European Union population. The European Union population that is disturbed by environmental noise is estimated to be about 100 million, and between 5 and 15% of this population suffers serious noise-induced sleep disturbance.
Noise during the night-time
Noise can be a factor of sleep disturbance, playing an important role alone or being associated to other environmental and/or individual factors. The main complaints about noise during night-time is not only related to the sleep period but also to its neighborhood. Thus, difficulty of falling asleep and of maintaining sleep after being awakened in early morning hours are often considered as major sleep disturbances, although they do not concern the sleep process per se.
Noise during sleep can provoke specific disturbances from sudden awakenings to sleep stage changes, short arousals and cardiovascular responses. These latter instantaneous autonomic responses to the occurring noises do not adapt on the long term basis, although a clear subjective habituation occurs after a few nights (Muzet and Ehrhart 1980, Muzet et al. 1981, Vallet et al. 1983).
The main effect of noise on sleep, however, is the sudden awakening. This event interrupts the sleeping process for a period of time going from a few seconds to several minutes and, as such, the awakening due to a single noise may constitute a major sleep disturbance. The repetition of these modifications throughout the night may lead to chronic sleep loss with its usual consequences such as chronic fatigue and sleepiness during daytime, and a global poor life quality.
The choice of a noise indicator
Noise level unit
Although the decibel A [dB(A)] is strongly attenuating the low frequency and partly the high frequency values to the benefit of the medium ones, it is easy to measure it and it has been chosen as the noise level unit in most of environmental public policies.
An integrated indicator gives a global noise exposure level over a given time period. This type of indicator is calculated by mathematical formula which represent a complex noise exposure in time and space. They represent tools which allow comparisons in noise exposure between different areas, times of day, and periods of the year. The global noise exposure is expected to be related to subjective complaints and health effects.
The elaboration of an integrated noise indicator over a year period is made in four steps:
choice of an instantaneous noise level unit;choice of a descriptor for a single noise event (aircraft noise);choice of a cumulative model for a day exposure;choice of a reference day for a year exposure.
France is using the "indice psophique", built according to the following rules:
noise unit: PNdB (for "perceived noise decibel");noise descriptor: maximum noise level maintained constant for one minute;noise exposure duration: 24 hours in two periods: day exposure (6 a.m. to 10 p.m.) and night exposure (10 p.m. to 6 a.m.), the later being calculated with a multiplying factor of 10.reference day: average daily traffic over the 12 months of the year.
However, the major inconvenience of this "indice psophique" is due to the fact that it is not possible to directly measure a noise level in PNdB. It has to be calculated. Its use has been decided in a context which tended to separate aircraft noises from other noise sources. Nowadays, this separation is psychologically unacceptable by the concerned populations and a global coherence has to be found.
The major advantage of this type of indicator is its ability to be used for defining specific noise zoning around airports and acoustical planning according to the defined areas. However, an integrated indicator has a limited operational value. Used for global noise description and long term planning, it does not help taking sanctions about an identified aircraft which does not respect noise limits. Penalty in this case, seems to be the only way to get a strict observance of established rules and noise limitations. Therefore, in addition to the integrated indicator it seems necessary to define a single noise event indicator to get a limit value above which a penalty will be systematically applied.
Single noise event indicator
The noise impact of a single noise event may be calculated by maximum noise level (LAmax) or by acoustic energy received during the time of this event. This acoustic energy is expressed by LAeq (T), where LAeq represents the average value of acoustic energy (power) during a given time period (T); here the duration of flying over, for example.
Towards aircraft identification and financial sanction in France
Taking into account all the above considerations, the French Authority on Airport Noise Control (Autorite de Controle des Nuisances Sonores Aeroportuaires : ACNUSA) is proposing to use two different indicators:
an integrated indicator : Lden, for equivalent continuous noise level for day, evening (with a multiplying factor of 5) and night (with a multiplying factor of 10) periods. This indicator is one of those recommended in the recent noise directive from the European parliament and the Council (1). This measure should help defining new protected areas around airports.a single noise event indicator. The analysis of surveys shows that an integrated indicator does not represent well the annoyance expressed by the exposed population and gives no indication about the observance of established landing and taking off procedures. The measure proposed is LAmax (1s) which can easily be monitored. It will be realized by ground measuring stations placed in different sites around the airports. This measure will allow to verify the respect of limit values imposed for different time periods. A maximal value will first be fixed for the nighttime period. The non-respect of this noise limit will imply financial sanctions for the contravening vessels. This will help excluding the noisiest aircrafts indistinctively of their classification into acoustic chapters.
In addition, it seems obvious that pilot and air controller training must be reinforced in order to take into account the environmental aspects (lesser noise procedure, knowledge of urban areas). An environmental priority must be recognized among objectives which, at the moment, deal mainly with aircraft capacity and scheduling.
|1||(1) Proposal for a Directive of the European Parliament and of the Council relating to the Assessment and Management of Environmental Noise (Draft), 2000.|
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