This study was designed to define the individual variables influencing subjective noise sensitivity in an urban population and to investigate the distribution of subjective noise sensitivity with regard to noise exposure. A general questionnaire, a ten-graded noise annoyance scale, the Weinstein's Noise Sensitivity Scale, and the Eysenck Personality Questionnaire were applied to a sample of 413 inhabitants of Belgrade. Distribution of noise sensitivity scores was normal and independent of noise exposure. No significant differences in average noise sensitivity scores were observed concerning gender and exposure to low (Leq < 55 dBA), and high level of traffic noise (Leq > 65 dBA). Multiple regression analysis revealed that neuroticism was the best individual predictor for SNS, for both sexes in the noisy area and for women only, in the quiet area (P < 0.001). Age, education level and introversion were not significantly related to noise sensitivity. Positive relation between reported noise annoyance and noise sensitivity was highly significant (P < 0.0001).
Keywords: noise, sensitivity, personality, urban, population
|How to cite this article:|
Belojevic G, Jakovljevic B. Factors influencing subjective noise sensitivity in an urban population. Noise Health 2001;4:17-24
| Introduction|| |
Noise level may not be of primary importance for the reactions of people living in noisy areas, and individuals may react quite differently in the same acoustical conditions (Lercher et al., 1998; Job 1996; Berglund and Lindvall 1995). This variance has partly been explained by the personality characteristic of a subjective noise sensitivity (SNS) (Stansfeld 1992). SNS is defined as "a factor involving underlying attitudes towards noise in general" pointing out a difference from noise annoyance as "an attitude towards a specified noise" (Anderson 1971). SNS may refer to sensitivity to annoyance by noise, or to a general susceptibility to a wide range of noises. Standardized questionnaires such as "Noise Sensitivity Scale" (Weinstein 1978), or "Noise Annoyance Sensitivity Scale" (Bregman and Pearson 1972), have been showed to be more reliable in predicting reactions to noise than short questions asking about noise sensitivity (Raw and Griffiths 1988). However, the complex and multidimensional nature of noise sensitivity as a personality attribute, creates difficulties to measure it in unambiguous terms. Meaning of noise, mood, motivation and other variables might influence subjective noise sensitivity in some specific situations (Levy-Leboyer et al. 1976). Nevertheless, a relative consistency and stability in a general level of noise sensitivity seems to exist. In favor of this assumption is the reported high correlation (men=0.63, women=0.74) of test-re-test scores on Noise Sensitivity Scale, among the residents of London, after a three year period (Stansfeld 1988). The investigation among residents along a highway prior and 4-16 months after its opening showed no evidence of adaptation of self-reported noise effects, annoyance or tendency to focus attention on the noise (Weinstein 1982). This could mean that a part of population tends to remain poorly adaptive to noise for longer periods of time. Approximately 19% of urban population is estimated to be sensitive to noise, with a pronounced criticism not only towards noise pollution but towards environmental noxious factors in general (Lercher et al., 1995).
It has been showed that SNS does not differ by sex (Langdon, 1976), but it might increase with age, and particularly in women (Thomas and Jones, 1982). Concerning social background, middle-class people have been found to be more sensitive to noise (Meijer et al. 1985). A consistent and significant correlation between SNS and noise annoyance was found in field studies (Stansfeld et al,. 1993; Moehle,r 1988). Concerning personality traits, neuroticism was more frequently found to be associated with SNS than with noise annoyance (Ohrstrom et al. 1988). A significant positive correlation was also found between introversion and SNS (Fuller and Robinson, 1973), but absence of this association was reported as well (Anderson, 1971).
Further clarification of the factors influencing SNS is needed for better prediction of the reactions of people living or working in noisy environments. The aim of this study was to define the individual variables influencing SNS in an urban population and to investigate the distribution of SNS with regard to noise exposure.
| Methods|| |
The study was performed in the center of Belgrade, where a homogenous social structure of population might be expected. Experimental zone was consisted of three streets with a high traffic density and the control area referred to three streets in a very quiet part of the town.
Ten houses numbers were chosen in the middle parts of each street, and all the adult dwellers were asked to fill in the questionnaire themselves. The response rate was 92% in the experimental zone, and 77% in the control area. The total of 413 filled questionnaires were collected (253 in experimental zone and 160 in the control area). The criterion for the shortest period of residence was one year.
Noise measurements were performed with the "Bruel & Kjaer" 4426 Noise Level Analyzer. Equivalent noise levels (Leq) were measured in three daily periods (9.00h-10.00h.14.00h15.30h.,18.00h-19.30h.), and in two night periods ( 0.00h-1.30h,3.30h-5.00h.), according to the procedures recommended by ISO (ISO 1982). The time interval of each measurement was 15 minutes, with the speed of sampling of 10 per second.
- A short general questionnaire referred to age, gender, education and period of residence. Education level was defined as low (elementary school), middle (secondary school) and high (university level).
- Noise annoyance was measured with a self-rating ten-graded scale. Grade 1 represented "not annoyed", while grade 10 represented extreme annoyance.
- SNS was assessed with the Weinstein's Noise Sensitivity Scale (Weinstein 1978), consisting of 21 statements with proposed degrees of agreement, graded from 0-5. A higher score on this scale refers to a higher sensitivity to noise. The questionnaire emphasizes the subject's affective reactions. The psychometric properties and the predictive validity of this questionnaire were shown to be satisfactory (Ekehammar and Dornic 1990).
- Personality traits of extra-introversion and neuroticism were measured with the Eysenck Personality Questionnaire (Eysenck and Eysenck 1975), comprising 65 questions with offered binary answers. Twenty-four questions referred to extrovert-introvert tendencies in behaviour (liveliness, sociability, talkativeness etc.). Other 24 questions were connected with neurotic tendencies in behaviour (worrying, irritativeness, anxiousness, nervousness etc.). Seventeen questions were used for the estimation of a subject's sincerity in answering. Each answer was given 0 or 1 point on the scales of extroversion, neuroticism and lying. The answers were considered reliable if the sum of points on the lying scale was under 8.
Statistical analysis of the interview data comprised the distribution of SNS and noise annoyance in the noisy and the quiet area. To test the normality of these distributions Shapiro - Wilks' W test was used. Spearman's rank order correlation test was used to assess the relation between SNS and noise annoyance. Multiple regression analysis was performed to investigate the influence of education level, neuroticism, introversion and age on SNS. Student's t-test was used for comparing average SNS scores in relation to age, gender and noise exposure.
| Results|| |
The results of the noise measurements have showed significant differences in the average 24h equivalent noise levels (Leq 24h) between the noisy area and the control zone of Belgrade (Leq 24h were 72 dBA and 45 dBA, respectively).
Distribution of education level was similar in the noisy and the quiet area (low - 2% and 10%, middle - 45% and 42%, high - 53% and 48%, respectively; x2 = 13.3, p > 0.05). The average period of residence was significantly longer in the noisy area, compared to the quiet zone (20 ± 15 years and 12 ± 10 years respectively, p < 0.001, Student's t - test).
No significant differences in average noise sensitivity scores were observed between the residents in the noisy and the quiet urban area (average noise sensitivity scores were 84.7 ± 16.7 and 81.9 ± 15.6 respectively, P > 0.05, Student's t-test). Positive relation between reported noise annoyance and SNS was highly significant in both areas (Spearman r = 0.485 and 0.324, P < 0.0001).
Distribution of the scores on the Noise Sensitivity Scale was normal both in the noisy area and in the control zone. However, the distribution of scores on the Noise Annoyance Scale was asymetrical, with the grouping towards higher scores in the noisy area, and towards lower scores in the quiet area. [Figure - 1],[Figure - 2].
Multiple regression analysis [Table - 1],[Table - 2] revealed that neuroticism was the best individual predictor for SNS, for both sexes in the noisy area and for women only, in the quiet area. No significant correlations were observed between age, education level, introversion and noise sensitivity, in both areas.
Ranking of the factors in [Table - 1],[Table - 2] are also the sequence of entry in the model. No significant effects were seen when the entering of factors was changed.
No significant differences in average noise sensitivity scores with respect to age and gender were found between the noisy area and the quiet zone [Table - 3].
| Discussion|| |
The results of our study indicate that SNS might be a personality variable independent of noise exposure and that significant correlation between SNS and noise annoyance may not be caused by noise. This is congruent with the findings that correlation coefficients between SNS and noise level are consistently lower than those between SNS and annoyance, and that sensitivity and noise exposure combined account for more variance in annoyance than noise exposure alone (Job, 1988). Thus, SNS might be an important predictor of the reactions of people living, or working in noisy environments.
Among the investigated individual variables the highest correlation with subjective noise sensitivity was found for neuroticism. This is in accordance with the findings of Ohrstrom et al. (1988) and Stansfeld (1985). In these studies it was showed that people with neurotic tendencies in behavior were more prone to negative effects of noise compared to more stable personalities. This is also congruent with the finding of Iwata (1984) that people sensitive to noise might have pronounced symptoms of tension, anger, nervousness, inferiority and anxiety.
It has also been shown that noise intolerance, as a major symptom of post-traumatic syndrome, might be more closely related to pre-traumatic neuroticism than to objective degree of trauma (Kashavan et al. 1981). Additional unfavorable factors for neurotic persons are worrying and anxiety, which might prevent them to cope successfully with noise as a stressor. These findings may partly be explained in the light of Broadbent's arousal theoretical concept, as a neurotic person tends to show a higher basic arousal level compared to more stable personalities (Broadbent, 1979).
We did not find a significant correlation between the level of introversion and SNS, an that is not congruent with the previous findings about a higher auditory acuity in introverted persons, who also prefer lower level of noise input than extroverts (Smith and Stansfeld 1968; Hockey 1972). Although Weinstein (1978) found that noise sensitive individuals showed a desire for privacy and were less comfortable in social situations, he questioned whether "the link between introversion and noise sensitivity is due to direct arousing effect of noise on the central nervous system, or to the fact that noise frequently has interpersonal significance and is seen as an intrusion by those who are ill at ease in social settings and prize privacy (psychosocial effect)".
Our findings of no significant correlation between age, gender and SNS are similar to those from the Langdon's field study (1976). We found no confirmation of the results of other studies about higher SNS scores among the elderly and women (Lukas and Dobbs, 1972; Nivison and Endresen, 1993).
| Conclusions|| |
This field study on an urban population showed that SNS was a personality variable independent of noise exposure. Neuroticism was showed to be the most important individual variable significantly influencing SNS. No significant relations of gender, age and introversion to SNS were found in the investigated population. Taking into account a highly significant correlation of SNS with noise annoyance, these findings might be helpful in predicting annoyance reactions to environmental noise in an urban population.
| Acknowledgment|| |
This study was supported by grant from the Serbian Ministry of Science and Technology, Contract No. 13T11, 1996-2000.
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Institute of Hygiene and Medical Ecology, University of Belgrade, School of Medicine, Pasterova 2, 11000 Belgrade, Serbia, and FR YUGOSLAVIA
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2]
[Table - 1], [Table - 2], [Table - 3]