Traffic Noise - Research Paper Example

TRAFFIC NOISE CHAPTER 1.0 Literature review 1 Causes of traffic noise Traffic noise is well referred to unwanted sound coming from vehicles operating on the roadways. Most of the traffic noise in the major cities and urban centers is caused by tires moving on pavements and also the sound produced by the vehicle engines. It has been the major cause of noise pollution in the 21st century. Noise pollution is evident in many areas in the society we are living in be it at home, in the street, in the cars, in public places and in the arenas. It’s however noted that even in the ancient times traffic pollution was experienced though not as much as it in the current century (Bergamo 2013, pg. 42). For example in the ancient Rome, chariots were banned from the streets at night because their wheels clattered on paving stones producing noise that disrupted sleep at night causing annoyance to the citizens. Horse drawn carriages have also been associated with noise in cities. They were banned in some countries centuries after the chariots were banned in Rome. Noise from vehicles have been reported to cause 80% of noise pollution in major cities and urban centers. The organization for Economic Development and Corporation estimated that 37% of the total population in U.S.A In 1980 was at risk of been annoyed by the increasing noise from the road traffic. The total miles of vehicular travel in the United States of America had annually increased at the rate of 3.1% growth from the year 1980 to the year 1996. In this regard, there was a suggestion of increase of the number of people been annoyed by the increase in the level of traffic noise in the environment they were living in. This report was in accordance to the survey done by the department of transportation (DOT). As the population increases and as the sources of information become more powerful and numerous, exposure to noise pollution increases. There is increasingly valuable sources of traffic pollution in the highway, rail and the air traffic (Salvi et al, 2009). This has adverse effects in our homes, social places, in the workplaces and learning environments. 1.2 Adverse effects of Traffic pollution Traffic causes noise pollution with a wide range of health economic and social effects to human beings. This have concluded after an intensive research by many professionals all over the world (Gärling, and L. Steg, 2010, pg. 47) It is an important environmental stressor in urban areas. This a great disturbance of sleep which results to major health effect. There is substantial inter-individual variance to the effects in reference to different individuals regarding to the difference in the sensitivity of the noise. It is most certain that the cumulative noise pollution in many is sufficient to cause impairment of hearing to many individuals living within the noisy areas. Stress can also be caused by elevated levels of noise which is also unhealthy. According to a research conducted in 2006, adverse health effects were found to be associated with traffic noise with over 5000 citations. Besides the health effects, traffic noise have many other effects to the society disadvantageous to those affected. It can lead to elevated accidents in the workplaces, may result to stimulation of aggression and also other antisocial behaviors. Noise may also be associate with the upset of domestic and wild animals. Noise interferes with sleep, communication, recreation and concentration. Even below the levels that are considered not harmful to hearing, it’s perceived as a danger signal during sleep. High visibility media campaigns were concluded by NIH panel so as to develop public awareness to the effects of noise especially on hearing and taught on the means of self-protection. 1.3 Measures to Traffic Noise Roadway noise contribution to a very high percentage of noise pollution in any urban center. May it be the noise from the tires and the surface and also the noise produced by the engines, they all contribute to the traffic noise contributing to noise pollution (Oosthuizen et al, 2012). It was until 1960s that the traffic noise started to be measured in a widespread manner and coming with appropriate solutions towards cabbing the situation started been put into place. Some motor vehicles have been banned from the urban centers though this have shown insignificant reduction of noise pollution. Traffic noise intensity have been shown to be governed by a number of factors including traffic operations such as the speed of vehicles, mix of trucks and also the age of the vehicle fleet, tire types, the geometrics of the roadway and the roadway surface types. The geometry of area structures can also been shown to contribute to traffic noise. The noise from and powertrains can be denominated by driving at lower speeds. The level and impact of traffic noise can be reduced by reducing the level of traffic volumes because when the volume doubles, the noise level automatically increases by 3dBA (Kehtarnavaz et al, 2007, pg. 33). The types of vehicles in the urban centers could also be regulated because motorcycles, buses and emergency vehicles produce much higher level of noises as compared to other vehicles. The behavior of the drivers including over accelerating and applying emergency breaks may result to increase to high levels of noise. ABSTRACT CHAPTER TWO 2.0 Traffic Noise Sound have reported to affect all the activities of human and should therefore be considered in both the local and the regional authorities and taken into account during land planning. Unwanted sound is termed as noise. The degree of tolerance to different levels of noise by individuals varies and at varying times of the day. Sounds have different frequencies. Different identical noise levels at different frequencies are result to different response in the human ear. Weighting is a term used to correlate human response to noise. A weighting is the weighting system used for this purpose. The resultant level of the noise is termed as the A-weighted noise level (dBA). This is used to describe the environmental noise at a particular point and time. In situation with continues noises including the one produced by traffic, rustling trees and from industries create noise level that cannot likely be identified with any other type of noise. The daily cycle of human activities slowly changes the level of the noise. Nearby events of short duration produces sound in between the background noise causing an overall rapid increase in the unwanted sound levels. Such nearby events may include local trucks, loud sounds and the aircraft flyovers. According to a research done to evaluate the sensitivity of human to changes in the level of noise, kit was reported that a 3 dB increase in the level of sound was barely noticeable to human, while a 5 dB increase in the level of sound resulted to noticeable change. It was also found that a 10 dB increase in the level of sound would noticed be a s twice loud as the 5dB increase in the level of sound. The A-Weighted method represents the human ears ability to interpret the loudness of equal sound level throughout the audible frequency range. The mentioned scale is referenced to the sound wave frequency at 1000 Hz. When we look at an example, at 300 Hz, the interpretation of the sound by the ears would be 30 dB. At this frequency of sound it would be considered to be quieter than at the higher extreme of the scale which is 100Hz. There would be higher tolerance of the human ear to high sounds with lower frequencies than the higher noise levels at high frequencies. The factors that can lead to community complaining and getting annoyed include the following: a) The overall peak of the noise level which is represented by Laq (the constant equivalent to the level of the noise that contain the same amount of acoustical energy as the varying level of the noise) b) the duration of the exposure to the sound for it to considered to be noise and the time of the of the day when the noise is considered unbearable c) the level of disturbance of the noise which is well determined by finding the difference between the level at which the noise is at its peak and the level at which the noise is at the minimum level. 2.1.0 Main causes of Traffic noise Different variables are associated with traffic noises causing environmental noise pollution. Each variable has its level of contribution of the traffic noise and a different method of regulation. Some of them are easy to control while others cannot be altered. However efforts are been made at the various levels of controlling pollution with the sole aim of controlling the effect of the noise to human beings and other animals associated with him. We are going to look at this factors at these in much details. 2.1.1 Roadway Surface The surface nature of a road contributes to varying degree of noise. The chip seal road type of road is the loudest together with the grooved roads. The surfaces without much noise include the surfaces are concrete and without spacers this being the most quite type of road. Other types of surfaces such as the asphaltic surfaces produce average type of traffic noise (Chang 2012. Pg. 16). Rubberized asphaltic surfaces which are surfaces that are made using recycled old tires always quiet and is currently widely used in making roads in the effort to try and reduce the traffic noise. Rough roads also result to increase in the level of traffic noise when compared to the sounds produced by the same vehicles on a smooth road surface. 2.1.2 Traffic operations. This is another great cause of traffic noise in many urban areas and major cities in the United States of America. The speed of vehicles will significantly affect the level of the traffic noise. At high speeds, the traffic noise increases significantly. This is because the sound energy level have been found to increase and precisely doubles with an increment of ten miles per hour in the velocity of a vehicle. However this rule do not apply at low speeds because the noise produced due to acceleration and breaking dominate over the aerodynamic noise. Hybrid vehicles are found to produce low noise at low speeds therefore providing pedestrian safety during parking if they are reversing or even when maneuvering. This however do not apply to the hybrid vehicles when they are been driven at high speeds. 2.1.3 Types of Tires The type of tires fitted to the wheels of a vehicle have also been found to affect the level of traffic noise. The type of tire can cause up to 10 dB variations in the noise on the road ways. Quitter tires have relatively lower resistance to rolling and they therefore reduce noise pollution when such vehicles are been driven on the roadways. 2.1.4 Geometry of area Structures This is a very important input that highly contributes significantly to the level of traffic noise on the road surface and in towns and major cities. Buildings and other structures build along the road block sounds produced by speeding vehicles from reaching to people’s residential homes and work places (Fratta et al, 2010, pg. 26). In this case the sound is found to travel short distances unlike in areas that have no structures or walls along the roads. 2.1.5 Roadway geometrics. Propagation of sound is dependent on a number of factors in relation to geometrics. This is dependent on the overall geometry and will be highly affected by reflection, diffraction and ground wave attenuation also the refraction of the waves. Sound is diminished when its path is blocked by a terrain. Otherwise the sound will be enhanced if the named roadway is elevated so that the sound is broadcasted. 2.2.0 Determining the Impacts of Traffic Noise. In the modern world, transportation have been considered the major cause of environmental noise pollution. This is regardless of the economic development status of any country. Noise related research was vigorously conducted in U.S.A. The research was carried out in accordance to the Noise control Act of 1972. All the noise abatement and noise control programs were coordinated by the office of the Noise abatement and Control (ONAC) at the environmental protection agency (EPA). Since that period control of the traffic noise have been concern in the United States. According to an American housing survey conducted by the census bureau that involved 38 metropolitan areas, which basically included the metropolitan Atlanta, There was a conclusion of many noise related questions been raised to be solved. This survey was done during the late 1990s and the early 2000s. There was an indication of felt impact due to the traffic noise in about 29% of the target household units. 2.2.1 Methods used. There was a significant increase in the vehicular travel miles in the Metropolitan Atlanta which was experienced from the year 1980 to thee year 1996. The increase that was recorded was 119%. This increase was compared to the population growth of the metropolitan Atlanta which was recoded to be 53% during the same period of time. The high increase in the vehicular travel would definitely lead to negative impacts of the people residing in the area. The impacts would most probably be proportional to the rate of increase of the vehicular travel. A highly urbanized county in the metropolitan region (Fulton County) was comfortably selected for this. This place was suitable because it experienced high growth of the vehicular travel and at the same time it is a well urbanized are the providing conducive environment for the research. The total area of the Fulton County is approximately 1369km2 and has 14 municipal cities. The County also has been considered to be the largest in the metropolitan Atlanta in various terms including the housing units and the degree of urbanization. According to the Department of Transportation of Georgia, the County of Fulton has a well-developed road network which has an approximately total length of 2678.37 km which is appropriate and considered by many people to be used in transportation. The road was also suitable for the study since its preference by the road users was increasing therefore increasing the vehicular travel miles while at the same time the population of the Urban center was increasing at a high rate. There is also an interstate highway 285 that runs round the heart of the county. A high density road have also been available within the interstate road network. The detailed data set for this research was collected within the period from 2009 to 2011. Later the data analysis was conducted within the period between 2010 to the year 2011. 2.1.2 Data Collection The prediction of traffic noise level was determined using the model based procedure. The noise exposure level would require to be analyzed in areas with different factors of topography; building footprints and heights, the types of vehicles or their speed; the composition of vehicle types road and also vehicles, road networks including highways, arterials and local roads. Relevant data sets was therefore collected in various sites of Fulton County, the department of transportation of Georgia and the Atlanta Regional Commission (ARC) which is a metropolitan regional organization. The table one below is a summary of the data input used Data type Parameter Data producer Production year Data access constraints Building Footprints Fulton county 2009 Proprietary Heights Fulton county 2009 Proprietary Topography Elevation U.S Geological survey 2009 Public Road Network Georgia Department of Transportation 2009 Proprietary Vehicle Volume Georgia Department of Transportation 2009 Proprietary Type Atlanta regional commission 2009 Proprietary Speed Georgia department of transportation 2009 Proprietary Population Daytime and night time population Oak ridge National Laboratory 2009 Proprietary 2.1.3 Road Traffic Noise prediction. The data collected and recorded was taken both from the daytime and night time populations. Daytime population was used to represent a snapshot of daytime working plan where the children are considered to in their respective schools. The nighttime population in this research was used to represent those are considered to be at home at night. The described study used the traffic model of the U.S.A federal highway implementation in Soundplan which was used to produce two road traffic noise maps for daytime (7A.M to 10P.M) and nighttime which was recorded from 10PM to 7AM. Within the Fulton county. The daytime road traffic was represented by the symbol LD while the,traffic noise produced at night was represented by LN. Both LD and LN were computed with a constant sound pressure level (Leq) with a grid size of 90M to be consistent with the to the LandScan population data. Leq indicates a constant noise level over a given period of time. The equation below was used to evaluate the relationship between LD and LN. Leq, I h = Eli + A traffic (i) +Ad + As El is used to indicate to the empirical noise level of the ith vehicle type A traffic (i) indicates the the adjustment for traffic flow such as the speed and volume of the vehicle. Ad indicating the distance adjustment between the road and the receiver. As is an indication of all shielding and ground effects between the road and the receiver. 2.1.4 Annoyance and sleep Disturbance To estimate the percentage population of those annoyed and disturbed by traffic noise based on exposure to the levels of the noise, different results were recorded. This was recorded as the percentage of highly annoyed people (%HD) while the percentage of the people with high levels of sleep disturbance was recorded as (% HSD). This was used to determine the number of population of people affected by the high levels of traffic noise during the day and also at night. This was done at different spots and at different times of the day and the data used to predict the disease burden from environmental noise which was as a result of sound from the traffic. Chapter 3 3.0 Results The traffic noise estimates from the Fulton County collected and recorded in the table two below. Increments of two different decibels were used to represent the noise produced as a result of the traffic movements as it was suggested by the Environmental protection agency of the USA. The highest level of traffic noise was found to have occurred along the highways and the major roads of the states including the roadways in the small and big cities. The data collected and recorded was taken both during the day and at night. According to the data, the downtown of Atlanta was found to have a complex networks of non-arterial roads during the daytime and this was associated with production of high levels of noise to the residents and people working within the roads. It was noted that the noise recorded as been produced at tight was less as compared to the noise that was been produced during the day. The prediction results were analyzed and conclude that 109,967 people involved in the study, who were just 9.5% of the people involved in the daytime study, were found to be at high risk of been annoyed by the traffic noise in Fulton County. It was also predicted that 2.3 of the nighttime studied population was at high risk of having high levels of sleep disturbance. The aim of the study was to find out the impacts of traffic noise especially in causing annoyance and sleep disturbance. The results of the study are summarized in the table 2 below Daytime Annoyance Nighttime sleep disturbance City Total population Population affected Prevalence (%) Total Population Population affected Prevalence (%) Alpharetta 807 78 9.7 486 7 1.5 Atlanta 6,553 670 10.2 4,057 113 2.8 Chattahooche e Hills 7 0.04 0.6 21 0.04 0.2 College Park 259 29 11.3 200 7 3.7 East point 345 29 8.4 402 9 2.2 Fairburn 70 5 6.9 68 1 1.0 Hapeville 82 9 11.0 61 2 2.5 Johns Creek 569 34 5.9 602 5 0.9 Milton 209 12 5.7 173 0 0.3 Palmetto 24 1 5.2 34 0 0.4 Roswell 747 55 7.4 846 14 1.6 Sandy Springs 1,093 123 11.3 908 27 2.9 Union City 106 9 8.5 147 4 2.8 Fulton County 11,526 1,100 9.5 8, 572 196 2.3 The largest predicted number was found to be in Atlanta with 667, 016 people been involved in the study and this figure contributed to 61% of the county level estimate of the people highly annoyed. The cities that followed Atlanta were the cities of Sandy springs and the Alpharetta which recorded the number of highly annoyed people as 12329 and 7824 respectively. The three cities largely affected the number Fulton County with approximately 79% of the number of the people that were highly annoyed. In accordance to the impact of those whose sleep were affected, the highest number of people were found to be from Atlanta (11, 313) where the cities of Sandy Springs and Roswell followed with the number of people involved in the study recorded as 2662 and 1390 respectively. According to the research done on these towns, the conclusion showed that 78% of the people were affected by the traffic noise resulting to the disturbance of their sleep at night. Noise regulation Types of noise regulation A number of regulations have been set up In the US to help cope with the issue of traffic noise in the major cities and urban centers. People should be advised to put in effective this issues which will to a high percentage reduce the effect of the noise to people and other negative effects that come up with the noise. Among others, the main measures would include the following. Subjective Emission These are regulations that are set forward which allows the a government official to decide if a source of the sound output is acceptable without necessarily involving the use of measurements to determine whether the sound is disadvantageous to the listeners. It is not also necessary to put a specific listener to be used to determine whether the sound would be considered noise interacting with the working of the people within the location. Example of such regulations include the setting of the plainly audible terms on the properties belonging to the public. Subjective Immission The subjective immission regulations set allow an officer to decide on whether the sound that a listener receives is within an acceptable level or not. This is done without the need to take the measurements of the sound produced to determine whether the level of the sound can be considered to be noise (Fratta et al, 2010). In this regulation there is also no need to regard the specific power of the sound that is generated during the emission. The best example in this type of sound regulation is the terms set to regulate sound in plainly audible or noise disturbance on private property. Objective Emission. Unlike the above discussed regulations, in the objective emission measurements are required to to regulate the sound level to avoid it from reaching the level of been considered noise. In this case an official is required to make measurements of the output of a source of sound emitted. The measurements taken assist in determining the level of the sound is to been considered as noise. However in this case there is no need to involve a specific listener. In this case there are a number of examples and regulating the maximum level of sound produced by the output in vehicles is one of them. This is a suitable method that lowers the level of traffic noise in streets. Objective Immission. It is a fourth form of regulation of the sounds to reduce the effect of noise in roadways. In these regulations, an official is required to measure the sound that is received by a listener to determine whether it is within the acceptable range. In this case there is no need of the regard to the specific sound power generated by the source of the sound. The examples to this form of regulation are the maximum sound levels allowed on the property lines. Other measures that can be used to regulate sound levels to minimize the effect of noise are; The use of noise barriers along some major roadways and the highways. This is a common practice done with the aim of lowering the levels of the noises for adjacent properties. The examples are the correct use of the noise walls and the berms that reflect sound waves with medium and high frequencies. A sound barrier selection should be chosen to fulfill the purpose and have good qualities that will increase the performance therefore giving the best results. In such a case the sound barriers chosen should be designed in a way that that will favor the overall performance. The most common types of building materials used including the use of wood, masonry and metal have surfaces that are hard to reflect sound. The walls or barriers made using such materials are referred to as reflective barriers and they do reflect sound that strikes them. In this process some energy is transmitted through the walls but the bulk of it is reflected back. The direction of the reflected sound will probably be in the direction of the source of the noise produced. The sound that hits the surfaces can be refracted to different directions depending on the nature of the wall surface and the roughness of the material used to build the wall. The shape of the wall also contributes to the degree of reflection and refraction of the sound. The use of sound absorptive materials in building the interior of buildings is effective to eliminate unwanted sound in the buildings. The mitigation of a sound can be affected by the geometry and the location of the barriers. When two reflective sounds are built on each side of a roadway, the resulting effect is having the formation of sound canyon which resonate with the reflective sound from each side of the road (Michael Minor & Associates 2006, Pg.56). This uses the same method and results in the absorption of the produced sound therefore it elimination and the end result been the avoidance of produce traffic noise and the immediate effects that come with the same. Figure 1. Sound is made to reverberate between two walls made to reflect sound. The process of reverberation can be avoided by the use of absorptive barriers. There is also a number of other situations that favor the use of absorptive materials in making the sound wall barriers. These will include the following; Sound Barriers on the Roadways Service Drive When a vehicle is as tall as a building or else taller than the building, the likeliness of reflections is obvious and the reflection such cases is critical. This increases the sound levels of the receiver by 3 t 5 dB, and even as high as up to 7dB in situation where there is reflective noise. Acoustical absorption used on the sound source side helps in reducing the effect of the sound. This provides the desired level of performance. Such conditions are recommended to be used on roadway barriers with semi-truck traffic on highways or the street which are put on the side of the receiver on the wall. This reduces the sound that is reflected and consequently the amount of noise that reaches to the receiver is minimal. Mechanical equipment noise. Placing both a mechanical equipment and a hvac equipment such an air cooled outdoor chillers, cooling towers and generators behind a source of sound, there is the mandating of sound levels due to zoning regulations (American Society of Civil Engineers.ICTE 2011) The havc equipment are placed between screen walls comprising of reflective materials. The unwanted sounds are mostly redirected to other directions which can also increase noise in through the unintentional redirected sound. Figure 2; Reflective sound enclosures and architectural screens. The use of acoustical absorption on the side of a sound source is a crucial thing in such sound enclosures. Use of supplemental acoustical absorption on the building side may also be required. Use of absorptive sound barriers. Materials that can be used to make absorptive barriers in buildings are in different varieties. The highest percentage of this materials are made up hard materials that include wood, metal sheets and HDPE and also masonry (Castro-Lacouture et al, 2014). They are all used with the aim of provide loss of produced sound. There is a variation of acoustical materials used. Fiberglass and mineral wool are the major materials that are used in the making of the acoustical absorptive material. The above two mentioned materials are good to be used because they can become wet hence no moisture retention. Their function can therefore not be distracted by been rained on. The material used should provide maximum effect by absorbing a wide range of p sound frequencies. There should be maximum elimination of unwanted sound. Read More