MAPPING ON INTERNAL AND EXTERNAL NOISE LEVELS

Transcription

1 A WRITE UP ON MAPPING ON INTERNAL AND EXTERNAL NOISE LEVELS BY ADEBIYI-WILLIAMS YETUNDE (ARC/09/7342) & ADEKUNLE ELIZABETH TOLUSE (ARC/09/7345) SUBMITTED TO THE DEPARTMENT OF ARCHITECTURE, SCHOOL OF ENVIRONMENTAL TECHNOLOGY, FEDERAL UNIVERSITY OF TECHNOLOGY AKURE, ONDO STATE. COURSE TITLE: ACOUSTICS AND NOISE CONTROL COURSE CODE: ARC 507 COURSE LECTURERS: PROF O.O. OGUNSOTE ARC S.A.GANIYU JULY 2014

2 TABLE OF CONTENTS 1.0. Abstract 2.0. Introduction 3.0. Noise mapping 3.1. The strategic noise mapping process 3.2. Types of noise maps 3.3. Global Positioning System (GPS) 3.4. Possible Errors in Noise mapping 3.5. Spectral noise maps 3.6. External noise level 3.7. Pictures Showing Example of Noise Maps 4.0. Conclusion References

3 1.0. ABSTRACT Everybody including the noise regulation bodies are increasingly relying on spectral information in order to assess the acoustical behaviour of materials and structures and the effects of noise on people. Nevertheless, the new European Union Directive on the assessment and management of environmental noise reinforces the A-weighted equivalent level (with appropriate night and evening corrections) as the preferred indicator for noise mapping. Considering that noise maps are a powerful zoning and planning resource, the idea of reporting the mean spectrum of noise at each selected location at different times is proposed and thoroughly justified. The preference for A-weighting-based indicators has led naturally to their adoption for noise mapping. Noise maps, being an important tool for diagnosis, zoning and planning purposes, should render as much information as possible as regards the prevailing noise over a given area. The aim of this paper is to introduce spectral noise maps as an alternative to traditional maps capable of providing such information.

4 2.0. INTRODUCTION Noise assessment as regards its effects on the human being has been carried out for many years using the A-weighted sound pressure level along with some related indicators, such as the equivalent level, LAeq, or the day-night level, LAdn. Widespread availability of relatively inexpensive sound level meters capable of directly performing such measurements in addition to the success in the use of those indicators for the prediction of effects of noise such as hearing impairment (ISO, 1990), and to a lesser degree, annoyance (Schultz, 1978; Fidell et al., 1991; Miedema et al., 1998; Miedema et al., 2001), have certainly influenced the universal acceptance of the A weighting. This has led, in turn, to the widespread adoption of A-weighting-based ordinances and regulations for community noise control and abatement, creating an increased demand for A-weighted sound level meters. Consequently, manufacturers virtually flooded the market with this sort of instruments, making it ever more difficult to depart from the general trend. It could even be argued that the universal adoption of the A-weighting might have been decided on too early, without sufficient evidence. In fact, its adoption has relied on several misconceptions. Firstly, it was assumed that noise effects on human beings are closely related to the sensation of loudness, which is clearly not the case (as shown by the example of the noise of a leaking tap in the night). Secondly, it was accepted that the response of the ear to pure tones could be extrapolated to combinations of them, or even to wide-band noises, in a linear fashion. Finally, the A weighting had been originally intended for the assessment of sound between 24 db and 55 db, but it is used to measure much louder sounds and it has led to the adoption for noise mapping.

5 3.0. NOISE MAPPING Noise map is the graphical representation of the sound level distribution existing in a given region, for a defined period. It is also a map of an area which is coloured according to the noise levels in the area. At times, the noise levels may be shown by contour lines which show the boundaries between different noise levels in an area. For instance, the noise levels may rise as a vehicle approaches, and reduce again after it has passed which could cause a short-term variation in noise level. A typical noise map gives a geographical general view noise levels that appear in each area of a plant.. There are several models for making noise maps. Softwares used for noise mapping are LimA, CadnA, Code Tympan, IMMI, Predictor, Sound Plan, noise3d online The Strategic Noise Mapping Process A seven step approach to noise mapping is recommended. Each stage is defined by preceding stages so that requirements and specifications are captured ahead of the datasets. The stages are: Stage 1 Define Areas to be Mapped Stage 2 Define Noise Calculation Methods Stage 3 Develop Dataset Specification Stage 4 Dataset Production Stage 5 Develop Noise Model Datasets Stage 6 Noise Level Calculations Stage 7 Post Processing and Analysis

6 3.2. Types of noise maps There are two types of noise maps using input of measured noise levels: Short or long-term measurement-based, where no account is taken of the XYZ position of the sources Calculated maps based on an acoustic model where reverse engineering is used to determine source levels based on measurements. The reverse engineering process can be simple, with no restrictions placed on the possible source noise levels, or can be more advanced including more complex estimations of the possible source noise levels Global Positioning System (GPS) can also help in determining measurement position It is an all-weather, continuous satellite navigation system that automatically identifies position and time. Connecting GPS to any transportable measurement unit can automatically identify position, date and time for speedier reporting, modelling, calculation and mapping, and accurate position data makes it easier to repeat noise measurements at the same position. An example of noise monitoring terminal achieved by GPS logging.

7 Using a GPS unit with a sound level meter 3.4. Possible Errors in Noise mapping Errors can be: Bias: This global error results in too big or too small noise contours. The following action planning will be fair and efficient as the hot spots are correctly identified. However, there may be too much or too little investment. This can be reduced through noise map calibration (see below). Error: This results in wrong placement of the noise contours at certain positions. The following action plan will be inefficient as hot spots may be incorrectly identified. This can be reduced through local calibration 3.5. Spectral Noise Maps One of the aims of traditional noise maps is to provide a graphic representation of a series of pertinent noise data, either measured or computed, over a given geographic area. Those data may be the hourly, daily or annual equivalent level, the associated statistical levels, Ln, or any other convenient indicator. In order to convey visual information in an attractive fashion, level contours such as those used in topographic maps are customarily drawn. Areas between adjacent contours may be coloured or shaded according to an agreed scale. This representation has the advantage that with a simple visual inspection one may get a fair idea of the location and magnitude of the main noise pollution issues. However, costs incurred to elaborate a noise map (including the planning and

8 performance of the required measurements) are high enough to make it advisable to allow other uses for the information. For instance, it can be used as a basis for a noisezoning ordinance, which would attempt to preserve quiet areas (the so-called acoustic sanctuaries) from future noisy activities. Another very interesting use for noise maps is to provide quantitative and qualitative data useful for urban infrastructure planning as well as building projects. It is well known that whenever the effects of noise or the acoustic response of a space, material, or structure are to be assessed, it is necessary to have spectral information of the noise. The same is true for any situation in which engineering criteria are to be applied. This is the result of the frequency-dependent nature of acoustic phenomena. With the introduction of computational techniques for handling large amounts of data, traditional maps have turned gradually into geographic information systems (GIS), i.e., data bases containing information pertaining to each relevant location in a given geographic area. An important feature of these systems is the possibility of linking and correlating different variables, often resorting to simple mathematical or statistical relationships. For instance, the percentage of highly annoyed people may be computed from the noise exposure, or from traffic flow along the nearest street (Miedema, 2001). Noise maps are no longer just a static picture, but instead an interactive resource in which the same basic information may be combined in new ways to produce meaningful results. Spectral information of noise is particularly suitable for its inclusion in a GIS. Indeed, being a multidimensional property, its direct representation on a conventional map would require the use of several layers (one for each band). This would not be very practical.

9 3.6. Mapping On External Noise Level Contours of noise levels at the facade of a building, It represent levels from 69 db(a) in the purple zone to 79 db(a) in the blue zone. Contours of noise levels at the facade of a building Its representing change in levels from 54 db(a) in the yellow zone to 75 db(a) in the blue zone.

10 3.7. Pictures Showing Example of Noise Maps

11 4.0. CONCLUSION This write up has given a comprehensive outline of how sound level measurements can be used in noise mapping and how GPS can help in determining measurement position. It described the different ways that measurements can be used in noise maps. The write up has also given a clear understanding on how noise map serve as a strategic planning, noise reduction tool and aid for decision making on internal and external noise matters. Noise mapping also serves as a strategic planning tool to keep noise levels from proposed new infrastructures; it helps in the reduction of the adverse effects caused by excessive noise levels. Noise mapping also identifies the number of people exposed to different levels of external noise which also predicts indoor noise levels, determining the effect of noise proposed noise barriers and also providing advice on noise management techniques.

12 REFERENCES Clarke, J.A. (2001) Energy Simulation in Building Design. Crawley, D.B. & Hand, J.W. (2006) Contrasting the Capabilities of building energy performance simulation programs. Building and Environment, 43 (4), pp DataKustik GmbH (2004) Cadna/A for Windows. ISO 532:1975 Acoustics - Method for calculating loudness level ISO :1982 Acoustics - Description and measurement of environmental noise Part 1: Basic quantities and procedures Miedema, Henk M. E.; Vos, H.: Exposure-response relations for transportation noise. Journal of the Acoustical Society of America 104 (6), December