M. Björkman

Noise annoyance with regard to neurophysiological sensitivity, subjective noise sensitivity and personality variables

To evaluate the relation between annoyance to environmental noise, general neurophysiological sensitivity, subjective noise sensitivity and other individual characteristics, experiments were undertaken in which 93 subjects assessed their subjective annoyance after exposure to noise under laboratory conditions. Evaluations were made of the discomfort threshold for pulsating sound, the light discomfort, and heat and cold discomfort. The heart rate and discomfort after exposure to a series of impulse noises was also determined. Subjective noise sensitivity, attitudes to noise, mood and personality characteristics of the subjects were evaluated using questionnaires. The results show that the annoyance after exposure to noise was not closely related to the general neurophysiological sensitivity, measured as discomfort threshold for noise, heat, cold and light; or to the heart rate reaction or discomfort after exposure to impulse noise. The annoyance was highly correlated with subjectively reported noise sensitivity and with the attitude to noise. There was also a relationship with neuroticism, measured with the EPI scale. It is suggested that the subjective noise sensitivity, attitude and neuroticism for the definition of noise sensitivity be defined in future studies of long term effects of noise exposure.

Annoyance due to low frequency noise and the use of the dB(A) scale

Abstract A laboratory experiment was carried out to evaluate the relative annoyance of a low frequency noise and reference noises at the same dB(A) levels. Four continuous fan noises centered at 80, 250, 500 and 1000 Hz were used as exposure noises. A total of 98 test subjects were exposed for 4 × 30 min periods to two of the exposure noises at two noise levels, while studying. Questionnaires were subsequently used to evaluate annoyance at noise levels between 40 and 70 dB(A). The results indicate that the low frequency noise is more annoying than the reference noises at levels over 40 dB(A). The set of equal-annoyance curves obtained in this study showed that the dB(A) unit underestimated annoyance for a broadband continuous low frequency noise by 3 dB for levels around 65 dB(Lin) and by 6 dB for levels around 70 dB(Lin).

Community noise annoyance: Importance of noise levels and the number of noise events

Abstract Two studies have been performed to evaluate the influence of maximum noise levels and the number of events on the annoyance reaction. The first study was performed in 18 different areas in five European countries and the second study in the city of Gothenburg in 14 different areas. The results showed that the equal energy related index did not describe the reaction between noise and the extent of annoyance in an exposed population in an optimal manner. When the number of noise events and the maximum noise levels were analyzed separately, it was found that an increase in the number of noise events led to an increase in the extent of annoyance up to a breakpoint, after which a further increase in the number of events had no effects on the reaction. The maximum noise level influenced the extent of annoyance independently from the number of noise events in the way that an increase in the maximum noise level from the most noisy event led to an increase in the extent of annoyance. It was also found that the number of heavy vehiches was a good descriptor for the number of noise events in road traffic noise.

Effects of noise-disturbed sleep: a laboratory study on habituation and subjective noise sensitivity

The effect of road traffic noise from heavy vehicles during the night was investigated in a two week laboratory experiment. Body movements, heart rate, subjective sleep quality, mood and performance was evaluated among two different groups of subjects, non-sensitive and sensitive to noise. Acute physiological effects, increased heart rate and an increased number of body movements, in connection with noise events were found and neither of these reactions decreased towards the end of the noise period. A significant effect on subjective sleep quality was found only among the sensitive subjects. No habititation was seen for the negative influence of noise on sleep quality, mood and performance.

EFFECTS OF NIGHT TIME ROAD TRAFFIC NOISE - AN OVERVIEW OF LABORATORY AND FIELD STUDIES ON NOISE DOSE AND SUBJECTIVE NOISE SENSITIVITY

Abstract This paper presents an overview of research on sleep and noise at the Department of Environmental Hygiene, University of Gothenburg. Different methods were developed to study primary and after effects of night time road traffic noise on sleep. Three one-week laboratory experiments were undertaken to study the relevance of different noise descriptors—Leq, maximum peak noise level and number of events with high peak noise levels—for sleep disturbance effects. The noise exposure was either single noise evenys or a continuous, even road traffic noise. It was concluded that Leq was not related to sleep disturbance effects. Peak noise levels were significantly related to subjective sleep quality and body movements. Results from a third continuing study showed that there is a threshold for effects of the number of single noise events on sleep quality. Habituation to noise among subjects with differing noise sensitivity was studied in a two-week experiment. A significant noise effect on subjective sleep quality was found among sensitive subjects only. No habituation was seen for the negative influence of noise on sleep quality, mood and performance. Long-term effects of road traffic noise were also investigated in a field survey among 106 individuals. This study revealed the presence of a decrease in sleep quality as well as psycho-social effects on tiredness and mood, together with increased reports of headaches and nervous stomach. As in the laboratory study, sensitive individuals were more affected by noise than less sensitive individuals.

Aircraft noise annoyance contours: Importance of overflight frequency and noise level

Abstract Social survey studies to assess the presence of general annoyance and activity disturbances were made in 38 areas around 9 airports. The noise exposure was expressed as the number of overflights/24 hours and the dB(A) level from the noisiest aircraft type. An increase in the number of overflights led to an increase in the extent of annoyance and activity disturbances up to a level of 50 overflights. The results indicate that the number of events is of limited value in describing annoyance caused by aircraft noise exposure and that the noise levels of noisy types of aircraft are more important. The data suggest that a more accurate description and prediction of the extent of annoyance in a population can be obtained by using the dose-response relationships developed in this study.

An experimental evaluation of annoyance due to low frequency noise

Annoyance due to environmental noise from various sources constitutes an important public health problem. Extensive work has been performed to obtain a basis for dose response curves, which can later be used for regulation purposes. Using such data, limits for noise exposure have been suggested or enforced for noise from aircraft, trains and road traffic. The estimation of the noise exposure for environmental noise is usually performed using the dB(A) unit. This is based upon early experiments where equal loudness curves were constructed by exposing test subjects to mainly pure tones of various frequencies for short exposure periods (e.g. Fletcher and Munson 1933, Churcher et al1937, Robinson and Dadson 1956). Experience from practical public health work demonstrates that this concept for judging annoyance can be questioned. Complaints to Local Health Authorities are frequently raised concerning low frequency sounds, and annoyance is reported, although dB(A) levels fall well below current limits. Sources oflow frequency noise, such as heavy vehicles, ventilation installations and compressors have increased in number in urban areas. In Sweden a recent source of low frequency noise is the use of heat pumps which extract heat from the air. There has been a rapid rise in the number of heat pumps owing to their ability to reduce heating costs. The pumps and compressors used, radiate low frequency noise, usually dominated by frequencies in the range 63-125 Hz. This is not a high noise level according to current noise limits, seldom exceeding 40 dB(A) outdoors. Despite this, many heat pumps have been reported as sources of annoyance to people living in the vicinity as shown by complaints received by Local Health Authorities (Persson and Rylander 1986). To further study annoyance from low frequency noise, we have performed studies in a laboratory environment. Subjects were exposed to two different noises of the same dB(A) levelbut where one of the noises contained a higher proportion oflow frequencies. The annoyance experienced by the subjects was assessed after a 30 minute exposure.

Laboratory annoyance and different traffic noise sources

Abstract The acute annoyance reaction to different noise sources (lorries, aircraft, mopeds and trains) was investigated in a laboratory experiment. Students were exposed to different noise climates at noise levels 70 and 80 dB(A) for 25 minutes, and their reactions were subsequently assessed by using a questionnaire. Their general sensitivity to noise was also evaluated. The results demonstrated that L eq gave the best correlation with annoyance. However, lorry noise was found to be less disturbing than aircraft noise at the same L eq value. This was more pronounced if the different noises were compared at equal peak dB(A) levels. The results suggest that other factors such as the irregularity of the noise or the individual experience of the noise are of importance for the annoyance reaction. A relationship was found between the general annoyance score and annoyance reactions in the laboratory. Questionnaires could thus be a suitable tool for identifying noise sensitive persons.

Aircraft noise annoyance and average versus maximum noise levels

A questionnaire study was performed in seven areas located around the airports of Landvetter and Save, Gothenburg, in an attempt to elucidate the extent of annoyance in populations exposed to aircraft noise. Noise exposure was estimated as the energy equivalent level (Aircraft Noise Level--FBN) or as the number of aircraft with levels that exceeded 70 dBA, combined with the maximum noise level. The results were compared with data obtained from the earlier Scandinavian Aircraft Noise Investigation. The results supported the conclusion that the annoyance reaction is better related to the number of aircraft and the maximum noise level than to energy equivalent levels for noise exposure.

Laudness, annoyance and dBA in evaluating low frequency sounds

The study reported here was undertaken to evaluate annoyance and loudness of low frequency sounds, to establish a reason for the discrepancy between the dB(A) unit and annoyance after exposure to low frequency sounds. Annoyance was evaluated by 98 test subjects who were exposed for 4 × 30 minute periods while studying. Four continuous fan noises centred at 80, 250, 500 and 1000 Hz were used as exposure noises. The relative annoyance of a low frequency noise and reference, noises were evaluated at the same dB(A) level using category scales. Noise levels betwen 40 and 70 dB(A) were included. Loudness estimates for pure tones at 63, 80, 250 and 1000 Hz were made by 12 subjects using magnitude estimation. Equal loudness contours were obtained at 45, 60 and 75 dB SPL. The loudness functions and contours derived were largely in agreement with ISO R/226, 1961. The estimations of loudness were higher than the degree of annoyance for these exposure noises. This effect became less pronounced towards the lower frequencies. The relation of the annoyance contours and the dB(A) demonstrates that the dB(A) weighting underestimates annoyance for frequencies below about 200 Hz.