Environmental acoustic quality in Jeddah urban sites

Applied Acoustics 17 (1984) 261-274

Environmental Acoustic Quality in Jeddah Urban Sites Kamel A. Elshorbagy* Faculty of Engineering, Alexandria University, Alexandria (Egypt)

(Received: 21 June, 1983)

SUMMARY Surveys of physical exposure to noise at urban sites in Jeddah city indicate that noise from road traIh'c is very intensive. Relatively high instant sound levels (90 dB(A) and higher) were recorded on a number of congested, as well as freely-[towing traJfic, roads. Values of the statistical indicators Lio, Lso, L9o and Lan were determined for indoor domestic noise and comparisons with current western standards show that the levels determined exceeded the limits of dissatisfaction given by those standards. Overall sound pressure levels measured inside typical university offices indicate that the presence of individual room-units of air-conditioning impairs the acoustic quality in those environments. The results of a social survey on noise perception in residential areas are in good agreement with the above findings, indicating that 89 per cent of people interviewed were substantially disturbed by traffic noise. The results of this research, however, demonstrate the necessity .for the application of a traffic noise control programme on Jeddah main roads and also the need for attention to be paid to the indoor acoustic quality of homes and offi'ces.

INTRODUCTION E n v i r o n m e n t a l noise p o l l u t i o n has been recognized in recent years as a serious threat to the quality o f life in m o s t developing and industrialized * Present address: FMES, King Abdulaziz University, P.O. Box 9034, Jeddah (21413), Saudi Arabia. 261 Applied Acoustics 0003-682X/84/$03-00 © Elsevier Applied Science Publishers Ltd, England, 1984. Printed in Great Britain

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Kamel A. Elshorbagy

nations. As a result, the protection of people against problems caused by noise--for example, task and sleep interference, temporary and permanent induced threshold shifts of hearing and damage to the hearing system--is now considered a national goal for central governments, as well as local health protection agencies. In a developing society like that of Jeddah city, a rapid rate of urbanization, accompanied by effective contributions to community noise, is well recognized. This includes the installation of industrial and constructional plants, the introduction of inter-city roads and highways, public transport and huge numbers of private cars and commercial vehicles and the employment of modern domestic appliances. Considerable effort has been made to formulate suitable ratings that quantify the annoyance caused by noise in populated areas. 1- ~ The type of any given acoustic environment defines the corresponding rating methods. The Noise Exposure Rating (NER), for example, is used to determine the severity of the problem caused to site workers by industrial noise. The x percentile exceeded sound level (Lx)--the sound pressure level exceeded x percent of the time--is a statistical indicator of noise used to describe community noise. In this context, the 1 and 10 percentile exceeded sound levels (L1, L~0) are considerably influenced by the noisier discrete events that may occur, whereas the 90 and 99 levels are only slightly influenced by nearby discrete events. The Equivalent Continuous Sound Level (L,,~) is the single most useful number for describing the noise environment over a given short period of time; it conveys the same sound energy as the actual time varying A-weighted sound. Another useful indicator is the Traffic Noise Index (TNI), usually used for describing community noise. It takes into account the degree of variability in observed sound levels to improve the correlation between traffic noise measurement and subjective response to noise. The Traffic Noise Index is defined as:

TNI = 4 ( L I o - L~o) + Lgo- 30 dB On the other hand, procedures for investigating public reaction to noise were devised and implemented. The most feasible procedure for obtaining a meaningful rating of a noise problem is the direct interview, by means of a social survey, with people subjected to the noise. The noise sensitivity scale devised by Weinstein, ~ for example, is a tool gaining greater recognition by researchers in noise pollution studies. Other

Environmental acoustic quality in Jeddah urban sites

263

procedures depending on ideas such as interviewing people in laboratory simulated sonic environments were also implemented, but with less degree of reliability. 8 The objective of the present work was to make a general evaluation of the acoustic status of different urban environments in Jeddah city without specifically surveying the noise field in very much detail. The study, however, is considered as a preliminary one that would open the door to more detailed surveys to be carried out in more specific environments. The work covered the rating of traffic noise in urban residential and commercial sites of the city, office noise as experienced at the King Abdulaziz University and indoor noise in typical Saudi homes. The results were supplemented by a social survey to investigate public opinion and peoples' reaction to their sonic environment.

MEASUREMENTS AND I N S T R U M E N T A T I O N Traffic noise Measurements were carried out at two sites representing inter-city moderate traffic density streets. The measurement locations are characterized as follows: Site I: Site II:

30m commercial street with partially congested traffic (Elrawis Street). 40 m urban inter-city one-way main road with freely flowing traffic (Khalid Ibn El-Walid Street).

Noise was recorded on a magnetic tape recorder for a period of 1 h at mid-day (11 am to 12 noon) for both sites I and II in addition to another period of 1 h ( 1 pm to 2 pm) for site II. During recording, the microphone was located 5 m away from the traffic centreline at a level of 1.20 m above ground. Sound pressure levels were also recorded at 5-min intervals, using a calibrated General Radio Sound Level Meter Type B-66S. The tape recordings were replayed and analyzed in laboratory where one-third octave frequency analysis of the noise and graphic records of the instant variation of SPL with time were obtained. A Bruel & Kjaer (B & K) frequency analyzer Type 2120 and a B & K graphic level recorder Type 2307 were used for the analysis.

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Kamel A. EIshorbagy

Office noise

Using the General Radio SLM, overall sound pressure levels in dB(A) were recorded inside twenty K A U offices for a period of 5 min in the middle of the working day, with the normal activities continuing. The recorded levels were used to determine an equivalent average SPL for every office. The offices were characterized by the nature of the work carried out in them and the number of occupants. It was noticed that all offices under consideration (like all other offices in the University) were air conditioned. Some of these offices had individual air-conditioning units (group A), while others were centrally air conditioned (group B). However, for the group A offices, the SPL measurements were repeated to cover the following conditions: (a) The air conditioner is switched off. (b) The air conditioner is switched on high speed. (c) The air conditioner is switched o n - - l o w speed. The measurements of SPL in group B offices were all carried out under one approximate constant temperature and normal working conditions. Indoor home noise

Two moderately comfortable flats were considered for the evaluation of indoor acoustic quality. Flat A is situated at AI-Hiindawiah (south-west of Jeddah) on the third floor and constitutes four rooms whilst flat B is located oil University Road (Kilo 6 of Makkah Road, south-east of Jeddah) on the second floor and constitutes five main rooms and a large hall. All rooms of both flats A and B have normal painted concrete walls with the same type of fittings, individual air-conditioning units and ceiling fans. Radios and television sets are located in the living rooms and the rooms of both flats have removable carpets. In both flats, sound pressure levels were determined during a 24-h period at 15-min intervals, at the centre of all rooms. A statistical analysis was made to evaluate the approximate values of the x percentile exceeded levels, L 10, Lso and Lgo, and also the day/night level (Ld,) with the standard penalty of 10dB applied to the sound levels during the period 7 pm to 7 am.

265

Environmental acoustic quali O' in Jeddah urban sites

SOCIAL SURVEY A social survey to assess the impact of noise on the public, both indoors and outdoors, was designed, developed and implemented in the form of direct interviews with adult males at different study sites. The questionnaire used was a simple one containing six groups of'multiple choice' type questions, written and conducted in Arabic, for a sample of 200 interviewees.

RESULTS A N D DISCUSSION Outdoor acoustic quality in residential areas adjacent to normal traffic roads Samples of the recorded variation in sound pressure level with time at the two sites under consideration are shown in Fig. l(a) to (c) and plots of the 90

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Kamel A. Elshorbagy

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5 min sampling of noise for a 1-h period at the two sites are shown in Fig. 2(a) to (c). From Fig. 2 it can be seen that the instant sound levels for site I vary between a minimum of 69 dB(A) and a maximum of 95 dB(A). The corresponding figures for site lI are 65 dB(A) and 86 dB(A) for the minimum and maximum levels, respectively. The qualitative variations in sound pressure level in Fig. l(a) to (c) are truly indicative. They reflect the fact that the flow of traffic at the second site (Khalid Ibn EI-Walid Street) is nearly free whilst that at the first site (A1-Rawis Street) is congested with superimposed frequent horn noises. During the time of observation, the traffic density at site I was measured

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as 1828 vehicles an hour while that at the site II was 2068 vehicles an hour. It was, however, noticed that tyre noise is the most effective noise on audible records although apparent frequent horn noise at site I was rated as much more intruding. Samples of the results of third-octave frequency analysis of the noise for a fixed period of time of observation are shown in Fig. 3(a) and (b). It can be noticed that the noise field at both sites is dominated by broad band sounds although higher levels exist in the medium frequency range (250-2000 Hz) at site I whereas high level bands persist at relatively lower and higher frequencies for the noise at site II. The sound levels indicated earlier are believed to be relatively high compared with those necessary to protect public health and welfare in residential areas, 9 although more elaborate specific research, including statistical analysis of the noise for longer periods of time, is needed to allow quantitative comparisons with available standards to be made. The effect of persisting high sound levels in Jeddah city streets is apparent from people's reaction to noise, as indicated in the results of the social survey given later.

Kamel A. Elshorbagy

268

Indoor acoustic quality inside Saudi homes Typical variations in sound levels inside flats in residential areas of Jeddah city during a 24-h period are shown in Fig. 4(a) and (b). Typical values of the statistical indicators L t o, L5o, L9o and Ld, were determined and are given in Table 1. The results in Fig. 4(a) and (b) indicate that the minimum background noise level inside the homes under investigation is 44 dB(A) whilst, due to domestic activities, the overall sound pressure level varies between this minimum level and a maximum of 75 dB(A). Substantial increases in sound pressure level occur during the day between 8 am and 12 noon and during the evening between 6 and 10 pm. This reflects the fact that, in eastern countries, people usually stay awake and active to fairly late hours. The results in Table 1 indicate that the acoustic levels inside Saudi homes are, again, very much higher than those specified by EPA to protect public health and welfare. A recommended figure of a) 80

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Environmental acoustic quality in Jeddah urban sites

269

TABLE 1 Values of Llo, Lso, Lgo and Ld. for the Sonic Environment Inside Typical Saudi Homes

Flat

Room function

A Reception A Living (1) A Living (2) B Reading B Living (1) B Living (2)

Llo dB(A)

Lso dB(A )

dB(A )

La. dB(A )

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45 66 69 65 67 69

41 41 59 61 61 62

51 76.5 76.2 71 72 74

Lgo

La, < 45dB(A) indoors for residential areas is, of course, very low compared with corresponding values that appear in Table 1, ranging between 51 and 76.5 dB(A). The main reason for the present higher values was the noise emitted from individual air-conditioning units that may be switched on for 24 h a day for most days of the year. Domestic appliances and outdoor noises, however, contribute to the indoor noise and could, in some instances, be more intruding, but not as long lasting as air conditioner noise. The lower sound levels and statistical indicators in Fig. 4(a) and Table 1, respectively, refer to rooms with no air conditioner in operation. However, it was noticeable during measurements that the operation of the usual TV sets, radios and stereo units was at relatively high levels. It was also noticed that room interior design is not adequate for sound conditioning and noise pollution control. For instance, acoustic plaster coating of the walls and floor carpeting could help to reduce reverberation indoors and thus reduce standing wave patterns of noise. Also, properly designed double glazed windows would certainly help in reducing extraneous noise intrusion.

Indoor acoustic quality inside university offices The instant values of sound pressure levels taken at the centre points of twenty university offices, used for various activities, are shown in Tables 2 and 3. It can be noticed for group A offices, that levels of the order of 62 to 72 dB(A) usually prevail when air-conditioning units are operated at high speed. However, these levels are very much reduced when the individual air-conditioning units are switched off. Unfortunately, due to the humid

Kamel A. Elshorbagy

270

TABLE 2 Instant Values of Sound Levels Inside University Offices, Group A Offices,* with Individual Air-Conditioning Units

Room No.

SPL (dB(A))

Number of occupants

Conditioner on~high

Conditioner on/low

Conditioner off"

1 2 3 4 5

65 63 68 67 62

58 59 64 60 59

52 53 53 50 48

2 3 1 1 1

6 7 8 9 10

65 68 63 66 72

60 63 60 63 69

55 54 55 55 68

1 1 4 3 1

Type o[ o]fice

Professor's office Professor's office Secretary's office Professor's office Office in small laboratory Professor's office Professor's office Student affairs office Secretary's office Computer room office

* All rooms are within the F M E S Old Building.

TABLE 3 Instant Values of Sound Levels Inside University Offices, G r o u p B Offices, with Central Air-Conditioning Systems

Room No.

1 2 3 4 5 6 7 8 9 10

Building

Geology Geology Geology Science Science Literature (20) Literature (20) Economics (38) Engineering (10) Engineering (10)

SPL (dB(A))

Number o[ oeeupants

40 41 65 70 49 5(L55 40 50-56 58 70 54 55 62

3 2 5 1 3 2 4 5 3 20

Type o/ q[fice

Museum office Librarian's office Sitting room Professor's office Laboratory office Staff office Student affairs office Professor's office Laboratory office Classroom

Environmental acoustic quality in Jeddah urban sites

271

and hot weather that dominates almost all days of the year, these airconditioning units work on a high speed setting almost continuously and thus emit high noise levels. However, when air conditioners are set on 'low speed' the sound levels are substantially reduced to the order of 58 to 64 dB(A) with an exception in office 10 where a higher level of 69 dB(A) was recorded due to noise from computers. It is also noticeable that low levels of the order 48 to 55 dB(A) were recorded inside this group of offices when air conditioners were switched off. Beranek et al. lO have reported a design objective for indoor A-weighted sound levels in large offices of 42 to 52 dB(A) to avoid speech interference. It can, however, be noticed that unless the air conditioners are switched off in the group A offices, the range of noise levels will never comply with such an acceptable objective. In the group B offices, the sound levels are normally in the range of 40 to 56 dB(A) except when working people are holding discussions when the level rises beyond this range (in room 3, the level was recorded as 65 to 70 dB(A) due to a normal discussion and in room 8 a range of 58 to 70 dB(A) was recorded for a professor teaching in his office). The fact that the group B offices are all centrally air conditioned and well carpeted would, however, explain the compatibility of the levels recorded in these rooms with the acceptable levels of the design objective given in reference 10.

Assessment of noise impact A comparison of peoples reaction to noise at home, at work and outdoors is given in Table 4. It is seen that the number of people who were disturbed TABLE 4 People's Reaction to Noise at Home, at W o r k a n d Outdoors, Jeddah, 1981

Individuals' reaction to noise

At home (per cent o[people)

At work (per cent t~[people)

Outdoors (per cent of people)

Those who are disturbed by noise Those who notice but are not disturbed Total of people w h o notice noise Those w h o do not notice noise

62 0 62 38

51 9 60 40

91 7 98 2

100

100

100

Kamel A. Elshorbagy

272

TABLE 5 Noises which Disturb People at Home, at Work and Outdoors

Description of noise

Percentage of people disturbed (200 questioned) When at home

When outdoors

When at work

Road traffic

28

87.5

16

Aircraft Industry/Construction works Domestic appliances Neighbours' impact noise (knocking, walking, etc.)

33 22-5 40

39.5 5 I-5 3-5

12 10 5.5

Children Adult voices Radio/TV

41 18-5 42.5

35

9

0

18.5 17-5 8

4.5 26 3

by noise at home is exactly the same as those who noticed the noise there. It is also seen that the two figures are similar for the outdoor and at-work environments. However, it is noticeable that people are more disturbed by noise when outdoors than when they are at home or at work. The kinds of noise which disturb people when at home, out of doors and at work are shown in Table 5. It is seen that while road traffic predominated outdoors, adult voices predominated at work. The indoor environment, however, is mostly impaired by domestic appliances, radios and television sets, in addition to children's activities. However, while the results in Table 4 indicate that the outdoor acoustic environment is disturbing for 91 per cent of people, the figures of Table 5 show that the noise due to road traffic is the major contributor to such reaction, whereas noise from industrial and constructional works came second. The results, as demonstrated above, are in good agreement with those obtained from physical measurements of noise, as reported earlier; the noise levels due to traffic on main roads conflict most with standard measures of satisfaction for community noise.

CONCLUSIONS The following conclusions were drawn from the combined results of the physical measurements and the social survey for the impact of noise on people in different environments.

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(1) Horn and tyre noises are the most intruding sounds contributing to the overall sound levels in Jeddah streets. The levels of noise in the congested traffic streets are, in many cases, higher than those set by international agencies to protect public health and welfare in residential areas. The dual traffic street has higher noise levels than the single-way traffic roads; level peaks of 90dB(A) and higher occur quite often due to horn, tyre and exhaust system noises in the dual traffic street. Large trucks (lorries) produce excessively higher noise levels than those emitted by smaller cars. (2) Typical noise levels inside fiats under construction are, in general, exceeding the limits of acceptability. The main sources of noise are air conditioners. Domestic appliances such as TV, radio sets, electro-mechanical kitchen facilities, etc., would also contribute to to the noise levels. (3) The acoustic environment of typical government offices in Jeddah is dominated by excessively high noise levels due to the operation of individual air-conditioning system units. However, central airconditioning systems provide an acceptable, quite pleasing, environment. ACKNOWLEDGEMENTS The Author wishes to thank FMES, King Abdulaziz University, Jeddah, Saudi Arabia, for providing necessary equipment and facilities needed to carry out this work. I am also grateful particularly to Mr I. Shabbaj and Mr F. Elmehmadi (the graduates of ENS Department) for providing assistance in measurements and computations. REFERENCES 1. P. N. Borsky, The use of social surveys for measuring community responses to noise environments. In: Transportation Noise. A Symposium on Acceptability Criteria, Seattle (J. D. Chalupnik (Ed.)), University of Washington Press, 1970, pp. 219-27. 2. R. Rylander, S. Sorensen and A. Kajland, Traffic noise exposure and annoyance reactions, Sound and Vibration, 47 (1976), pp. 237-42. 3. F. J. Langdon, Noise nuisance caused by road traffic in residential areas, Parts I and II, J. Sound and Vibration, 47 (1976), pp. 243-82. 4. H. S. A1-Samarrai and M. A1-Jawadi, Traffic noise and annoyance in Baghdad, Inter-noise (1981), pp. 537~,0.

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Kamel A. Elshorbagy

5. A. C. McKennel, Noise complaints and community action. In: Transportation Noises. A Symposium on Acceptability Criteria, Seattle (J. D. Chalupnik (Ed.)), University of Washington Press, 1970. 6. K. A. Elshorbagy and E. H. Zube, Environmental noise: A cross-cultural rating of the problem in urban eastern and western communities. Proc. Int. Symposium, Environmental Impact Assessment Current Status and Future Prospects, Crete, 1983. 7. N. D. Weinstein, Individual differences in reactions to noise, A longitudinal study in a college dormitory, J. Psychology, 63 (1978), pp. 4-466. pp. 4 466. 8. G. H. Cermak, Laboratory experiments on traffic noise annoyance. In: Community noise (R.J. Reppin and C.W. Rodman (Eds)), ASTM (Publication No. 692), Philadelphia, pp. 124 43. 9. Anon. Information on levels of environmental noise requisite to protect public health, EPA, March (1974). 10. L. L. Beranek, W. E. Blazier and J. J. Figwer, Preferred noise criteria (PNC) curves and their application to rooms, J. Acout. Soc. Am., ,50 (1971), pp. 1223-8.