1.5 million people in Norway (1/3 of the population) are exposed to transport noise levels exceeding recommended values. The aim of this thesis was to investigate how people react to such noise, what personality and environmental characteristics influence this experience, and if there any negative health consequences?
The current thesis belongs to the field of Psychology; more specifically to Environmental Psychology. Environmental Psychology emphasizes that persons and environments, even if they are separate entities, are continually involved in a series of interactions, both being mutually shaped by the encounter with the other. Interactionalism implies an increased awareness about the causal relationship between contextual background variables and outcome variables. Structural Equation Models (SEM) are chosen to investigate the interrelationships between variables.
Two major data sets are used. Data set 1 stems from 17 local environmental surveys carried out between 1987 and 2001, comprising a total of 19 000 respondents from the cities of Oslo and Drammen. The studies were conducted in 50 different subareas. Data set 2 derives from a socio-acoustic survey of 3262 persons in Oslo. Response rates were in the range 40-50% in data set 1, and 60% in data set 2. In both data sets noise levels inside and outside each participant’s dwelling were assessed using the Nordic Prediction Method for road traffic noise is used. The precision of the estimated noise exposure values hold a higher quality than what is normally used.
General relationships between noise exposure levels and annoyance from road traffic in Norway were established. Half of the population find road traffic noise highly annoying at 70 dB and somewhat annoying at 58 dB. Even if the respondents react stronger to a given noise level than respondents in other European studies, the results fits well with previous results on noise-annoyance relationships.
Noise level explains only about 20% of the variance in noise annoyance. Hence, there are a range of other variables that might potentially contribute to explaining why some people find noise bothersome, and others not. We were interested in the impacts of having an adverse neighbourhood soundscape. We therefore used the highest equivalent noise level attained within a radius of 75 meters of the apartment, and calculated a neighbourhood maximum difference indicator, Ldiff.max. This indicator explains a considerable amount of noise annoyance in addition to exposure at the most exposed façade. The “worst” cases can add 7 dB to the calculated residential exposure level.
We investigated whether income may influence annoyance levels directly, by high SES residents having better resources for dealing with a given noise level, or indirectly, by giving high SES residents a choice to live in less noisy areas. The SEM model that was developed helped to illustrate the dynamics of how noise annoyance is produced and socially distributed in a community. Income was (indirectly) related to noise exposure in a medium-sized city, but not in a larger metropolitan area. In line with previous results no (direct) relationship was found between noise annoyance and income.
The models were further elaborated. These models were instrumental in establishing relationships between noise, sleep disturbances, subjective health complaints and cardiovascular disease. No relationship was found between noise exposure or annoyance and cardiovascular disease. The close ties between noise sensitivity and subjective health complaints were used as an argument for paying close attention to the role of general vulnerability in future studies of noise health relationships. Sleeping problems due to road traffic noise have been suggested as a major contributor to stress-related negative health outcomes. We show that road traffic noise is only a moderate contributor to overall sleeping problems, and that subjective health complaints are linked to both sleeping problems and noise experience.
In line with core theoretical principles of environmental psychology the results of these papers point to the importance of looking at the noise health relationship in a broader environmental and psychological context. Future research should combine large-scale community studies with good quality individual exposure assessments. Alongside the pursuit of further knowledge of potential health effects of noise, we should therefore strive to gain further understanding of the causal mechanisms, with particular focus on the psychological and behavioural effects of noise.