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Traffic noise exposure and annoyance reactions
Journal
qf’Soundand
TRAFFIC
Vibration
(1976)
47(2). 237-242
NOISE EXPOSURE
,4ND ANNOYANCE
REACTIONS
R. RYLANDER Department
of Environmental Hygiene, University of Gotheburg, Gothenburg, Sweden
S. SORENSENAND Department
of Environmental
(Received
A. KAJLAND
Hygiene, National Environmental Stockholm, Sweden
19 June 1915, and in revisedfbrm
Protection
Board,
15 January 1976)
The relation between annoyance and exposure to traffic noise was studied in areas exposed to different levels of city traffic noise. A traditional social survey technique was used and the annoyance was evaluated as the percent very annoyed in population samples of about eighty persons. A relatively good relation was found between the annoyance and the traffic noise level expressed as L Aq or Loi. When noise levels in dB(A) or number of vehicles were related to annoyance a higher correlation was found for data from the heavy vehicles. If the noise level was expressed as the dB(A) value from heavy vehicles (buses, trucks) a dose-response relationship resembling that earlier found for aircraft noise was found.
1. INTRODUCTION Several studies have been published where the effects of environmental noise on the exposed population have been studied. Various expressions for annoyance have generally been used as the effect criterion, and dose-response relationships have been presented between the noise exposure level and the extent of annoyance. An important purpose of such studies is to establish a basis for planning and to develop forecasts on expected reactions when the exposure is altered. In these studies the noise exposure has usually been expressed as an index which takes into account the noise level as well as the number of events. The index will represent the mean noise exposure-the equal energy principle. Different weighting factors can then be used for the noise levels, the number of events and other factors which are considered to be of importance [ 11. The concept that the exposure effect is determined by the total physical noise exposure expressed as an average value has been questioned. In a study on aircraft noise annoyance, the correlation between exposure and the extent of annoyance was improved if the noise was expressed as the peak dB(A) value [2]. It was also found that the extent of annoyance increased with an increasing number of overflights but only up to a limiting value. A further increase in the number of exposures did not augment the extent of annoyance at equal dB(A) levels. This relation between noise exposure and the extent of annoyance has later been demonstrated also by results from a re-analysis of a French investigation [3] and from Dutch, German and Japanese studies [4]. In these studies strong dose-response relationship was found between the noise exposure expressed as the peak dB(A) level (the average noise level from the noisiest aircraft type using the airfield, calculated by using nominal noise contours) and the 237
238
R. RYLANDER,
S. SiiRENSEN
AND A. KAJLAND
reaction in terms of general annoyance or conversation interference given as the mean for groups of about 100 respondents. Against this background it was considered to be of interest to investigate whether the principle demonstrated for aircraft noise was also applicable to other kinds of environmental noises. This paper reports data from a study undertaken to investigate the relation between exposure to various levels of traffic noise and the extent of annoyance in the exposed populations. The study was designed to evaluate the importance of the dB(A) peak levels and the number of exposure events.
2. MATERIAL 2.1.
SELECTION
OF INVESTIGATION
AND METHODS
AREAS
The study was performed in the Swedish towns of Stockholm and Visby in residential zones in the city center as well as in suburban areas. Areas were selected where the number of vehicles per 24 hours ranged from 700 to 28,000. Within this variation of the number of total vehicles, areas were chosen where the proportion of heavy traffic varied. Information on the number of vehicles and the proportion of heavy vehicles was obtained from official statistics valid for the previous year. No significant changes in the traffic pattern had taken place since these statistics were compiled. 2.2.
INTERVIEW
INVESTIGATIONS
The population was defined as persons between 18 and 75 years of age, who had moved into the area at least one year earlier and had an apartment with windows facing the street. From this population a random sample was drawn for the interview investigation. The size of the population, the sample and the drop out in the different areas are shown in Table 1. 1 Population, sample and drop out in different investigation areas (S = Stockholm, V = Visby) TABLE
Area Sl s2 s3 s4 S5 S6 s7 S8 Vl v2 v3
Population 302 332 283 373 180 533 358 325 76 58 63
Sample
Drop out (n)
Drop out (%)
85 85 85 85 72 85 85 85 76 58 63
5 0 3 7 9 5 1 4 11 3 5
6 0 3 8 13 6 1 5 14 5 8
The social survey investigation was performed by using the traditional technique generally applied in studies of this kind. Prior to the personal interview, the respondents received an introductory letter which presented the investigation as a general survey of the quality of the environment. The interviews were performed by trained interviewers with earlier experience from investigations of this kind. The interview was masked and questions concerning traffic noise were part of a battery of questions on other sources of annoyance in the environment. The extent of annoyance in the different areas was expressed as the percent of the interviewed population indicating that they were “very annoyed” by traffic noise.
TRAFFIC
2.3.
NOISE EXPOSURE
-.-I;c)
AND ANNOYANCE
NOISE MEASUREMENTS
Noise measurements were performed shortly after the interview investigation had taken place. They were performed one meter above the ground in the open at a distance from the road which was equal to that of the houses where the respondents lived. The noise was recorded on a tape recorder (Nagra 521). The tapes were analysed in the laboratory and the equivalent continuous A weighted levels (LAq) as well as the level exceeded 1 y0 of the time (L,,) were calculated by using the noise levels measured and the number of vehicles obtained from official statistics for the different roads. The peak dB(A) level was estimated for passenger cars (light vehicles) and .buses and trucks (heavy vehicles). It was defined as the arithmetic mean of the noise levels from all vehicles in each category (light and heavy vehicles). A variation with a maximum of 4 dB(A) was sometimes present between noise values obtained at different houses in the same invest igation area. The noise level in the area was then expressed as the arithmetic mean of these values.
3. RESULTS The noise levels and the extent of annoyance in the different areas investigated are reported in Table 2. It is seen in the table that the noise levels, number of vehicles and number of heavy vehicles were present in different combinations in the different investigation areas. The desired variation of the acoustical parameters was thus obtained. TABLE
2
Trafic noise exposure and annoyance in difJerent inuestigatioll areas (S = Stockholm, V = Visby) Peak dB(A) Vehicles/24 hours Area Sl
s2 s3 s4 S5 S6 s7 S8 Vl v2 v3
800 3 600 7 600 900 3 800 7 300 28 000 18 200 1 003 3 324 700
84 108 228 144 570 1 200 2800 722 68 240 0
i Light vehicles
Heavy vehicles
70 70 64 74 62 72 68 74 79 79 76
80 79 72 82 72 80 79 81 89 90 -
L AQ
L 01
“,/, very annoyed
61 65 61 67 60 69 68 72 67 74 61
77 80 73 81 75 82 81 83 -
1 4 6 9 3 25 25 19 11 16 0
Figure 1 demonstrates the relation between the percentages of “very annoyed” in the different investigation areas and the noise exposure expressed as L,, and Lol. It is seen in the figure that the values are relatively highly related (the correlation coefficient rXv = 0.78 and 0.69). For a specific noise level, however, the variation in annoyance between different areas can be rather large. The relation between the log of the number of vehicles, irrespective of the noise level, and the extent of annoyance was 0.70 for the total number of vehicles and 0.75 for the number of heavy vehicles. The relations between the noise levels in peak dB(A) and the extent of annoyance irrespective of the number of vehicles was 0.19 for light vehicles and 0.31 for heavy vehicles.
240
R. RYLANDER, S. SiiRENSEN AND
A. KAJLAND
LAq
LOI
Figure 1. Relation between annoyance and traffic noise level expressed as (a) LAq and (b) LoI.
In the further analysis the relation between the number of vehicles and annoyance studied in areas where exposure to noise from the two vehicle categories was about the (light vehicles 70, heavy vehicles SO dB(A)). In these areas the relation between the number of vehicles and annoyance was 0.82 and between the number of heavy vehicles annoyance 0.98.
was same total and
30 2800
xx 1200
P 0” zoz : > z
X 720 X 240
IO-
x 144 X 228
t I
X68
x 108 x 84
x 570
1
I
I 70
80
90
Peak de(A)
Figure 2. Relation between annoyance and traffic noise level expressed as peak dB(A) and number of heavy vehicles. I
I
Heavy
,
vehicles
Figure 3. Relation between annoyance and number of heavy vehicles for areas exposed to around 80 dB(A) peak level.
TRAFFIC
NOISE EXPOSURE
AND ANNOYANCE
241
Figure 2 illustrates the extent of annoyance in relation to the peak dB(A) value from heavy vehicles. The number of heavy vehicles passing through the area has been inserted for each area. The figure shows that the majority of the areas were exposed to around 80 dE(A). Those areas are thus the only ones suitable for a further evaluation of dose-response relationships with reference to the number of exposures and the peak dB(A) value. The dose-response relation for these areas has been illustrated in Figure 3. The figure demonstrates that the extent of annoyance increased for areas exposed to a larger number of heavy vehicles. No difference in annoyance was found between the two areas exposed to 1200 and 2800 heavy vehicles per 24 hours.
4. DISCUSSIONS The annoyance has been reported here as the percentage of a group of exposed individuals who expressed that they were “very annoyed”. It would be desirable to define annoyance on an individual basis and relate it to the exposure level. In studies where this has been tried the correlation between individual annoyance and the exposure generally does not exceed 0.5 [5]. Apart from the noise exposure, the extent of annoyance is determined by a number of factors related to the individual. This explains why all reactions from “not annoyed” to “very annoyed” can be present in an area where the noise exposure is uniform. The individual annoyance thus cannot be related to a specific exposure level. For public health purposes the mean reaction in a population has to be used as the exposure criterion. The evaluation of general annoyance can be performed by using all degrees of annoyance obtained in the responses from the interview-“not annoyed” to “very annoyed”. It has been demonstrated, however, that the proportion of the population expressing that they are “very annoyed” is most closely related to the physical noise exposure and that this expression for annoyance is also closely related to other manifestations of discomfort [6]. A large number of questions relating to annoyance and the individual’s adaptation to his environment were asked in the interviews. The response to these questions can also be used to determine the presence of annoyance. Certain activity disturbances such as interference with conversation are very closely related to general annoyance and can equally well be used to express the extent of annoyance [6, 71. The different activity disturbances can also be weighted into indices of annoyance. As the relative importance of different activity disturbances varies at different exposure levels [6] this procedure might decrease the accuracy of the measure for annoyance. Psychological scales have also been proposed [8] but no experimental data have been presented which demonstrate that such scales increase the degree of accuracy for this kind of investigation. The correlation between the traffic noise level expressed as L,, or L,, and the extent of annoyance found in this study is fairly high, and comparable to relationships found in other studies. The correlation between the number of vehicles passing through the area and the extent of annoyance was almost as high as for the L,, or L,, values. This seems reasonable as the majority of areas investigated were exposed to about the same noise level. The only parameter which varied sufficiently for an independent evaluation was thus the number of vehicles. The correlation between the noise levels and annoyance was rather low, indicating that the number of vehicles is an important factor for the development of annoyance. When the different acoustical parameters for light and heavy vehicles werecompared, the correlation to annoyance was always larger for the heavy vehicles. The dose-response relationship for areas exposed to around 80 dB(A) from heavy vehicles demonstrated that an increasing number of heavy vehicles increased the extent of annoyance. No difference was present between one area exposed to 1200 and another exposed to 2800
242
R. RYLANDER,
S. SijRENSEN AND A. KAJLAND
parallel with the findings from studies on heavy vehicles per 24 hours. This is an interesting aircraft noise exposure evaluated with the peak dB(A) level principle. In this case annoyance increases at increasing overflight levels up to a level of about 50 per 24 hours. Above this value a further increase in the number of overflights does not increase the extent of annoyance at corresponding peak dB(A) levels. If the results from areas exposed to other noise levels than 80 dB(A) peak level were to follow the principles found for aircraft noise a larger number of heavy vehicles at lower dB(A) levels should be present before the annoyance would start to increase. At the higher noise levels the annoyance should be more extended for a lower number of heavy vehicles. Although the results from such areas reported in this study conform with this hypothesis (Figure 2) further data must be obtained before any firm conclusions can be drawn. To obtain this complete picture of the dose-response pattern it will be necessary to study additional areas exposed to lower and higher noise levels. Such studies should aim to include areas which were not sufficiently represented in this study, particularly 70 dB(A) areas exposed to a high number of heavy vehicles and additional 90 dB(A) areas. Such studies are in progress. If the present results were to be applied for practical use, an increased attention should be paid to heavy vehicles in terms of reducing their number or their peak noise levels. It is unlikely that actions taken towards the noise from light vehicles would affect the extent of annoyance unless the noise from heavier vehicles was considerably reduced towards the levels from the light traffic. During the revision of this work it has been brought to our attention [9] that a good correlation between the extent of annoyance and noise exposure is also obtained if the noise exposure is expressed as A = L,, + IO log N, where N is the number of heavy vehicles. The doseresponse relationship obtained with this index does not give the saturation phenomenon for the number of heavy vehicles as illustrated in Figure 3. The application of this expression for noise exposure does however support the main findings from this study: namely, that noise levels caused by heavy vehicles are the determinants for the extent of annoyance caused by traffic noise.
REFERENCES K. S. PEARSONS 1973 in Noise as a Public Health Problem. EPA Dot 550/9-73-008,7-24. D. Ward (editor). Systems for noise measurement. 2. R. RYLANDER, S. SORENSEN and A. KAJLAND 1972 Journal of Sound and Vibration 24, 419-444. Annoyance reactions from aircraft noise exposure. 3. R. RYLANDER, S. SORENSEN, A. ALEXANDRE and PH. GILBERT 1973 Journal of Sound and Vibration 28, 15-21. Determinants for aircraft noise annoyance-a comparison between French and Scandinavian data. 4. R. RYLANDER, S. SORENSEN and K. BERGLUND 1974 Journal of Sound and Vibration 36,399-406. Re-analysis of aircraft noise annoyance data against the dB(A) peak concept. 5. W. R. HAZARD 1971 Journal of Sound and Vibration 15,425U45. Predictions of noise disturbance near large airports. 6. S. SORENSEN, R. RYLANDER and K. BERGLUND 1974 in Noise as a Public Health Problem, EPA Dot 550/9-73-008 (W. Dixon Ward, editor), 669-677. Reaction patterns in annoyance response to aircraft noise. 7. L. M. WARD and T. SNEDFELD 1973 Environmental Research 6, 306-326. Human responses to high-way noise. 8. BIRGITTA BERGLUND, U. BERGLUND and T. LINDVALL 1975 Journal of Sound and Vibration 41, 33-39. A study of response criteria in populations exposed to aircraft noise. 9. Personal communication from a referee. 1.
qf’Soundand
TRAFFIC
Vibration
(1976)
47(2). 237-242
NOISE EXPOSURE
,4ND ANNOYANCE
REACTIONS
R. RYLANDER Department
of Environmental Hygiene, University of Gotheburg, Gothenburg, Sweden
S. SORENSENAND Department
of Environmental
(Received
A. KAJLAND
Hygiene, National Environmental Stockholm, Sweden
19 June 1915, and in revisedfbrm
Protection
Board,
15 January 1976)
The relation between annoyance and exposure to traffic noise was studied in areas exposed to different levels of city traffic noise. A traditional social survey technique was used and the annoyance was evaluated as the percent very annoyed in population samples of about eighty persons. A relatively good relation was found between the annoyance and the traffic noise level expressed as L Aq or Loi. When noise levels in dB(A) or number of vehicles were related to annoyance a higher correlation was found for data from the heavy vehicles. If the noise level was expressed as the dB(A) value from heavy vehicles (buses, trucks) a dose-response relationship resembling that earlier found for aircraft noise was found.
1. INTRODUCTION Several studies have been published where the effects of environmental noise on the exposed population have been studied. Various expressions for annoyance have generally been used as the effect criterion, and dose-response relationships have been presented between the noise exposure level and the extent of annoyance. An important purpose of such studies is to establish a basis for planning and to develop forecasts on expected reactions when the exposure is altered. In these studies the noise exposure has usually been expressed as an index which takes into account the noise level as well as the number of events. The index will represent the mean noise exposure-the equal energy principle. Different weighting factors can then be used for the noise levels, the number of events and other factors which are considered to be of importance [ 11. The concept that the exposure effect is determined by the total physical noise exposure expressed as an average value has been questioned. In a study on aircraft noise annoyance, the correlation between exposure and the extent of annoyance was improved if the noise was expressed as the peak dB(A) value [2]. It was also found that the extent of annoyance increased with an increasing number of overflights but only up to a limiting value. A further increase in the number of exposures did not augment the extent of annoyance at equal dB(A) levels. This relation between noise exposure and the extent of annoyance has later been demonstrated also by results from a re-analysis of a French investigation [3] and from Dutch, German and Japanese studies [4]. In these studies strong dose-response relationship was found between the noise exposure expressed as the peak dB(A) level (the average noise level from the noisiest aircraft type using the airfield, calculated by using nominal noise contours) and the 237
238
R. RYLANDER,
S. SiiRENSEN
AND A. KAJLAND
reaction in terms of general annoyance or conversation interference given as the mean for groups of about 100 respondents. Against this background it was considered to be of interest to investigate whether the principle demonstrated for aircraft noise was also applicable to other kinds of environmental noises. This paper reports data from a study undertaken to investigate the relation between exposure to various levels of traffic noise and the extent of annoyance in the exposed populations. The study was designed to evaluate the importance of the dB(A) peak levels and the number of exposure events.
2. MATERIAL 2.1.
SELECTION
OF INVESTIGATION
AND METHODS
AREAS
The study was performed in the Swedish towns of Stockholm and Visby in residential zones in the city center as well as in suburban areas. Areas were selected where the number of vehicles per 24 hours ranged from 700 to 28,000. Within this variation of the number of total vehicles, areas were chosen where the proportion of heavy traffic varied. Information on the number of vehicles and the proportion of heavy vehicles was obtained from official statistics valid for the previous year. No significant changes in the traffic pattern had taken place since these statistics were compiled. 2.2.
INTERVIEW
INVESTIGATIONS
The population was defined as persons between 18 and 75 years of age, who had moved into the area at least one year earlier and had an apartment with windows facing the street. From this population a random sample was drawn for the interview investigation. The size of the population, the sample and the drop out in the different areas are shown in Table 1. 1 Population, sample and drop out in different investigation areas (S = Stockholm, V = Visby) TABLE
Area Sl s2 s3 s4 S5 S6 s7 S8 Vl v2 v3
Population 302 332 283 373 180 533 358 325 76 58 63
Sample
Drop out (n)
Drop out (%)
85 85 85 85 72 85 85 85 76 58 63
5 0 3 7 9 5 1 4 11 3 5
6 0 3 8 13 6 1 5 14 5 8
The social survey investigation was performed by using the traditional technique generally applied in studies of this kind. Prior to the personal interview, the respondents received an introductory letter which presented the investigation as a general survey of the quality of the environment. The interviews were performed by trained interviewers with earlier experience from investigations of this kind. The interview was masked and questions concerning traffic noise were part of a battery of questions on other sources of annoyance in the environment. The extent of annoyance in the different areas was expressed as the percent of the interviewed population indicating that they were “very annoyed” by traffic noise.
TRAFFIC
2.3.
NOISE EXPOSURE
-.-I;c)
AND ANNOYANCE
NOISE MEASUREMENTS
Noise measurements were performed shortly after the interview investigation had taken place. They were performed one meter above the ground in the open at a distance from the road which was equal to that of the houses where the respondents lived. The noise was recorded on a tape recorder (Nagra 521). The tapes were analysed in the laboratory and the equivalent continuous A weighted levels (LAq) as well as the level exceeded 1 y0 of the time (L,,) were calculated by using the noise levels measured and the number of vehicles obtained from official statistics for the different roads. The peak dB(A) level was estimated for passenger cars (light vehicles) and .buses and trucks (heavy vehicles). It was defined as the arithmetic mean of the noise levels from all vehicles in each category (light and heavy vehicles). A variation with a maximum of 4 dB(A) was sometimes present between noise values obtained at different houses in the same invest igation area. The noise level in the area was then expressed as the arithmetic mean of these values.
3. RESULTS The noise levels and the extent of annoyance in the different areas investigated are reported in Table 2. It is seen in the table that the noise levels, number of vehicles and number of heavy vehicles were present in different combinations in the different investigation areas. The desired variation of the acoustical parameters was thus obtained. TABLE
2
Trafic noise exposure and annoyance in difJerent inuestigatioll areas (S = Stockholm, V = Visby) Peak dB(A) Vehicles/24 hours Area Sl
s2 s3 s4 S5 S6 s7 S8 Vl v2 v3
800 3 600 7 600 900 3 800 7 300 28 000 18 200 1 003 3 324 700
84 108 228 144 570 1 200 2800 722 68 240 0
i Light vehicles
Heavy vehicles
70 70 64 74 62 72 68 74 79 79 76
80 79 72 82 72 80 79 81 89 90 -
L AQ
L 01
“,/, very annoyed
61 65 61 67 60 69 68 72 67 74 61
77 80 73 81 75 82 81 83 -
1 4 6 9 3 25 25 19 11 16 0
Figure 1 demonstrates the relation between the percentages of “very annoyed” in the different investigation areas and the noise exposure expressed as L,, and Lol. It is seen in the figure that the values are relatively highly related (the correlation coefficient rXv = 0.78 and 0.69). For a specific noise level, however, the variation in annoyance between different areas can be rather large. The relation between the log of the number of vehicles, irrespective of the noise level, and the extent of annoyance was 0.70 for the total number of vehicles and 0.75 for the number of heavy vehicles. The relations between the noise levels in peak dB(A) and the extent of annoyance irrespective of the number of vehicles was 0.19 for light vehicles and 0.31 for heavy vehicles.
240
R. RYLANDER, S. SiiRENSEN AND
A. KAJLAND
LAq
LOI
Figure 1. Relation between annoyance and traffic noise level expressed as (a) LAq and (b) LoI.
In the further analysis the relation between the number of vehicles and annoyance studied in areas where exposure to noise from the two vehicle categories was about the (light vehicles 70, heavy vehicles SO dB(A)). In these areas the relation between the number of vehicles and annoyance was 0.82 and between the number of heavy vehicles annoyance 0.98.
was same total and
30 2800
xx 1200
P 0” zoz : > z
X 720 X 240
IO-
x 144 X 228
t I
X68
x 108 x 84
x 570
1
I
I 70
80
90
Peak de(A)
Figure 2. Relation between annoyance and traffic noise level expressed as peak dB(A) and number of heavy vehicles. I
I
Heavy
,
vehicles
Figure 3. Relation between annoyance and number of heavy vehicles for areas exposed to around 80 dB(A) peak level.
TRAFFIC
NOISE EXPOSURE
AND ANNOYANCE
241
Figure 2 illustrates the extent of annoyance in relation to the peak dB(A) value from heavy vehicles. The number of heavy vehicles passing through the area has been inserted for each area. The figure shows that the majority of the areas were exposed to around 80 dE(A). Those areas are thus the only ones suitable for a further evaluation of dose-response relationships with reference to the number of exposures and the peak dB(A) value. The dose-response relation for these areas has been illustrated in Figure 3. The figure demonstrates that the extent of annoyance increased for areas exposed to a larger number of heavy vehicles. No difference in annoyance was found between the two areas exposed to 1200 and 2800 heavy vehicles per 24 hours.
4. DISCUSSIONS The annoyance has been reported here as the percentage of a group of exposed individuals who expressed that they were “very annoyed”. It would be desirable to define annoyance on an individual basis and relate it to the exposure level. In studies where this has been tried the correlation between individual annoyance and the exposure generally does not exceed 0.5 [5]. Apart from the noise exposure, the extent of annoyance is determined by a number of factors related to the individual. This explains why all reactions from “not annoyed” to “very annoyed” can be present in an area where the noise exposure is uniform. The individual annoyance thus cannot be related to a specific exposure level. For public health purposes the mean reaction in a population has to be used as the exposure criterion. The evaluation of general annoyance can be performed by using all degrees of annoyance obtained in the responses from the interview-“not annoyed” to “very annoyed”. It has been demonstrated, however, that the proportion of the population expressing that they are “very annoyed” is most closely related to the physical noise exposure and that this expression for annoyance is also closely related to other manifestations of discomfort [6]. A large number of questions relating to annoyance and the individual’s adaptation to his environment were asked in the interviews. The response to these questions can also be used to determine the presence of annoyance. Certain activity disturbances such as interference with conversation are very closely related to general annoyance and can equally well be used to express the extent of annoyance [6, 71. The different activity disturbances can also be weighted into indices of annoyance. As the relative importance of different activity disturbances varies at different exposure levels [6] this procedure might decrease the accuracy of the measure for annoyance. Psychological scales have also been proposed [8] but no experimental data have been presented which demonstrate that such scales increase the degree of accuracy for this kind of investigation. The correlation between the traffic noise level expressed as L,, or L,, and the extent of annoyance found in this study is fairly high, and comparable to relationships found in other studies. The correlation between the number of vehicles passing through the area and the extent of annoyance was almost as high as for the L,, or L,, values. This seems reasonable as the majority of areas investigated were exposed to about the same noise level. The only parameter which varied sufficiently for an independent evaluation was thus the number of vehicles. The correlation between the noise levels and annoyance was rather low, indicating that the number of vehicles is an important factor for the development of annoyance. When the different acoustical parameters for light and heavy vehicles werecompared, the correlation to annoyance was always larger for the heavy vehicles. The dose-response relationship for areas exposed to around 80 dB(A) from heavy vehicles demonstrated that an increasing number of heavy vehicles increased the extent of annoyance. No difference was present between one area exposed to 1200 and another exposed to 2800
242
R. RYLANDER,
S. SijRENSEN AND A. KAJLAND
parallel with the findings from studies on heavy vehicles per 24 hours. This is an interesting aircraft noise exposure evaluated with the peak dB(A) level principle. In this case annoyance increases at increasing overflight levels up to a level of about 50 per 24 hours. Above this value a further increase in the number of overflights does not increase the extent of annoyance at corresponding peak dB(A) levels. If the results from areas exposed to other noise levels than 80 dB(A) peak level were to follow the principles found for aircraft noise a larger number of heavy vehicles at lower dB(A) levels should be present before the annoyance would start to increase. At the higher noise levels the annoyance should be more extended for a lower number of heavy vehicles. Although the results from such areas reported in this study conform with this hypothesis (Figure 2) further data must be obtained before any firm conclusions can be drawn. To obtain this complete picture of the dose-response pattern it will be necessary to study additional areas exposed to lower and higher noise levels. Such studies should aim to include areas which were not sufficiently represented in this study, particularly 70 dB(A) areas exposed to a high number of heavy vehicles and additional 90 dB(A) areas. Such studies are in progress. If the present results were to be applied for practical use, an increased attention should be paid to heavy vehicles in terms of reducing their number or their peak noise levels. It is unlikely that actions taken towards the noise from light vehicles would affect the extent of annoyance unless the noise from heavier vehicles was considerably reduced towards the levels from the light traffic. During the revision of this work it has been brought to our attention [9] that a good correlation between the extent of annoyance and noise exposure is also obtained if the noise exposure is expressed as A = L,, + IO log N, where N is the number of heavy vehicles. The doseresponse relationship obtained with this index does not give the saturation phenomenon for the number of heavy vehicles as illustrated in Figure 3. The application of this expression for noise exposure does however support the main findings from this study: namely, that noise levels caused by heavy vehicles are the determinants for the extent of annoyance caused by traffic noise.
REFERENCES K. S. PEARSONS 1973 in Noise as a Public Health Problem. EPA Dot 550/9-73-008,7-24. D. Ward (editor). Systems for noise measurement. 2. R. RYLANDER, S. SORENSEN and A. KAJLAND 1972 Journal of Sound and Vibration 24, 419-444. Annoyance reactions from aircraft noise exposure. 3. R. RYLANDER, S. SORENSEN, A. ALEXANDRE and PH. GILBERT 1973 Journal of Sound and Vibration 28, 15-21. Determinants for aircraft noise annoyance-a comparison between French and Scandinavian data. 4. R. RYLANDER, S. SORENSEN and K. BERGLUND 1974 Journal of Sound and Vibration 36,399-406. Re-analysis of aircraft noise annoyance data against the dB(A) peak concept. 5. W. R. HAZARD 1971 Journal of Sound and Vibration 15,425U45. Predictions of noise disturbance near large airports. 6. S. SORENSEN, R. RYLANDER and K. BERGLUND 1974 in Noise as a Public Health Problem, EPA Dot 550/9-73-008 (W. Dixon Ward, editor), 669-677. Reaction patterns in annoyance response to aircraft noise. 7. L. M. WARD and T. SNEDFELD 1973 Environmental Research 6, 306-326. Human responses to high-way noise. 8. BIRGITTA BERGLUND, U. BERGLUND and T. LINDVALL 1975 Journal of Sound and Vibration 41, 33-39. A study of response criteria in populations exposed to aircraft noise. 9. Personal communication from a referee. 1.