Environmental Engineering Reference
In-Depth Information
instantaneous noise level experienced during a given brief period of time. Cumula-
tive measurements usually consider noise on an energy averaged basis over a specific
time period and can be differentiated into daytime, evening and night. The FAA in
the US uses the community noise equivalent level (CNEL), while the UK commonly
uses L
eq
as the long-term average noise exposure measure. Many authors are critical
of cumulative noise measures and there is evidence that annoyance is more highly
correlated with a measure of single extreme noise events rather than cumulative
energy measures (Bjorkman and Rylander, 1995).
To explore the nature and extent of the potential damage to health and well-being,
research in this area has included:
•
attitudinal surveys of residents by questionnaires and focus groups;
•
direct physiological monitoring of individuals in laboratories or field settings
with actual or reproduced noise events;
•
archival interrogation of medical records in affected localities compared with unaf-
fected areas. Individuals may seek medication to relieve the general stress syn-
drome, which may express itself in a number of minor ailments or specifically as
'insomnia' due to night flights. This course of action has given researchers another
investigative tool in the form of the prevalence of patients visiting local medical
practitioners for hypnotics and sedatives.
Due to difficulties applying clear 'dose-response' relationships in the health domain,
some authors and governments have looked at other disciplines to determine the extent
of the perceived problem. For example, in order to derive an economic value of com-
munity disturbance, house price devaluation in noise-affected areas has been studied
(Tomkins et al, 1998). This tendency to avoid moving into, or relocating out of, noisy
areas presents a further confounding factor for research studies in that the study pop-
ulation is potentially self-selected, with coping survivors in the worst affected areas.
A recent approach has been to investigate the records of complaints made directly
to the airports in relation to aspects of the airport's operations in an attempt to under-
stand their objections, and any underlying patterns of complaining behaviour. This
is an approach that has been suggested by a WHO task group (Berry and Jiggins,
1999), who included longitudinal studies in a list of research needs in order to inves-
tigate the causal connections between mental health effects, annoyance and sponta-
neous complaints.
In addition to noise exposure, there are numerous modifying factors - for exam-
ple, personal benefits from the airport (employment or frequent use) - that can mask
or modify the apparent adverse affects (Flindell and Stallen, 1999). This is a major
confounding issue that can obscure relationships in many studies in this area.
Annoyance
Annoyance is a subjective reaction frequently reported in response to environmental
noise. The reported level of annoyance is obviously influenced by many non-acoustical
modifying factors - for example, attitudinal, personal and contextual factors (such
as general health, attitude to the noise source or noise sensitivity) - that act to obscure
attempts to investigate cause-and-effect relationships. Nevertheless, determining the
