Environmental Noise Control - Essay Example

Environment Noise Control INDEX Serial Number Topic Page No 2 2 Introduction 3 3 Literature review 4 4 Experiment and Method 8 5 Data Analysis 10 6 Conclusions and Recommendations 11 7 Appendix 12 8 References 13 Abstract Environmental noise, usually called Noise pollution in technical venues, is displeasing human or machine created sound that disrupts the environment. The dominant form of noise pollution is from transportation sources, principally motor vehicles. Principal noise health effects are both health and behavioral in nature. Unwanted sounds can seriously damage and effect physiological and psychological health. For instance, noise pollution can cause annoyance and aggression, hypertension, high stress levels, tinnitus, hearing loss, and other harmful effects depending on the level of sound, or how loud it is. Furthermore, stress and hypertension are the leading causes to health problems, whereas tinnitus can lead to forgetfulness, severe depression and at times panic attacks. Passive noise control involves constructions done to reduce the noise level in roadways and busy roadways. The treatments include insulation, silencers, vibration mounts, damping treatments, absorptive treatments and conventional mufflers like the ones used on today's automobiles. The Bradford City Centre is one such place where the noise levels are very high. This report aims at making a comprehensive study about the present noise levels and the expected noise levels after the transformation that it is to undergo. Introduction In recent years, traffic noise - the unpleasant, unwanted sounds generated on our nation's streets and roadways - has been of increasing concern both to the public and to State officials. At the same time, modern acoustical technology has been providing better ways to lessen the adverse impacts of roadway traffic noise. Many of these acoustical techniques are now being employed by government agencies, roadway planners and designers, construction engineers, and private developers to reduce the impact of this noise. The loudness of sounds (that is, how loud they seem to humans) varies from person to person, so there is no precise definition of loudness. However, based on many tests of large numbers of people, a sound level of 70 is twice as loud to the listener as a level of 60 (Wikipedia) Literature Review The level of roadway traffic noise depends on three things: (1) The volume of the traffic (2) the speed of the traffic, and (3) the number of vehicles in the flow of the traffic. Generally, the loudness of traffic noise is increased by heavier traffic volumes, higher speeds, and greater numbers of vehicles. Vehicle noise is a combination of the noises produced by the engine, exhaust, and tires. The loudness of traffic noise can also be increased by defective mufflers or other faulty equipment on vehicles. Any condition (such as a steep incline) that causes heavy laboring of motor vehicle engines will also increase traffic noise levels. There are other more complicated factors that affect the loudness of traffic noise. Roadway traffic noise is never constant (FHWA). The noise level is always changing with the number, type, and speed of the vehicles which produce the noise. However, it is usually inconvenient and cumbersome to represent traffic noise in this manner. A more practical method is to convert the noise data to a single representative number. Roadway noise is being attacked with a three-part strategy: motor vehicle control, land use control, and roadway planning and design. The responsibilities for implementing these strategies are shared by all levels of government. Efforts are being made to either reduce or prevent traffic noise impacts by either obtaining quieter vehicles or by controlling future development near roadways (FHWA). The first part of the strategy goes right to the source of traffic noise: the vehicles. For example, vehicles can be designed with enclosures for the engine; fans that turn off when not needed, and better mufflers. Quieter vehicles would bring about a substantial reduction in traffic noise along those roads and streets where no other corrective measures are possible. Regulations can place a limit on the noise which new vehicles can make. In addition, many local and State governments have passed ordinances or laws requiring existing vehicles to be properly maintained and operated. Unfortunately, due to limitations in technology, these regulations can only partially reduce the noise created by traffic. The best that can be expected is a 5 to 10 dBA decrease in the noise level (Kelleher, 1995). Where this is insufficient, other measures must be used. The second part of the strategy, Land Use Control, calls for the control of future development. Sometimes, complaints about roadway traffic come from occupants of new homes built adjacent to an existing roadway. Prudent land use control can help to prevent many future traffic noise problems in these areas. Such controls need not prohibit development, but rather can require reasonable distances between buildings and roads as well as "soundproofing" or other abatement measures to lessen noise disturbances (Bruel & Kjaer, 2007). Like for example, less noise-sensitive commercial buildings can be placed next to a roadway, with residences farther away. The third part of the roadway noise reduction strategy is roadway planning and design. Early in the planning stages of most roadway improvements, roadway agencies do a noise study. The purpose of this study is to determine if the project will create any noise problems. First, the existing noise levels of a roadway are measured or computed by models. Then, the agency predicts what the noise levels will be if the project is constructed. If the predicted noise levels are above the suggested noise criteria, the noise study must consider measures that can be taken to lessen these adverse noise impacts. Some noise reduction measures that are possible on existing roads or on roads that are being rebuilt include creating buffer zones, constructing barriers, planting vegetation, installing noise insulation in buildings, and managing traffic. Buffer zones are undeveloped open spaces which border a roadway. Buffer zones are created when a roadway agency purchases land or development rights, in addition to the normal right of way, so that future dwellings cannot be constructed close to the roadway. This precludes the possibility of constructing dwellings that would otherwise experience an excessive noise level from nearby roadway traffic. An additional benefit of buffer zones is that they often improve the roadside appearance. However, because of the tremendous amount of land that must be purchased and because in many cases dwellings already border existing roads, creating buffer zones is often not possible. Noise barriers are solid obstructions built between the roadway and the homes along the roadway. Effective noise barriers can reduce noise levels by 10 to 15 decibels, cutting the loudness of traffic noise in half. Barriers can be formed from earth mounds along the road or from high, vertical walls (. Earth mounds have a natural appearance and are usually attractive. However, an earth mound can require quite a lot of land if it is very high. Walls take less space. They are usually limited to 25 feet in height for structural and aesthetic reasons. Noise walls can be built of wood, stucco, concrete, masonry, metal, and other materials. Many attempts are being made to construct noise barriers that are visually pleasing and that blend in with their surroundings. However, barriers do have limitations (FHWA). For a noise barrier to work, it must be high enough and long enough to block the view of a road. Noise barriers do very little good for homes on a hillside overlooking a road or for buildings which rise above the barrier. Openings in noise walls for driveway connections or intersecting streets destroy the effectiveness of barriers. In some areas, homes are scattered too far apart to permit noise barriers to be built at a reasonable cost. Vegetation, if high enough, wide enough, and dense enough (cannot be seen through), can decrease roadway traffic noise (Bruel & Kjaer, 2007). A 200-foot width of dense vegetation can reduce noise by 10 decibels, which cuts the loudness of traffic noise in half. It is often impractical to plant enough vegetation along a road to achieve such reductions; however, if dense vegetation already exists, it could be saved. If it does not exist, roadside vegetation can be planted to create psychological relief, if not an actual lessening of traffic noise levels. Insulating buildings can greatly reduce roadway traffic noise, especially when windows are sealed and cracks and other openings are filled. Sometimes, noise-absorbing material can be placed in the walls of new buildings during construction. However, insulation can be costly because air conditioning is usually necessary once the windows are sealed. Managing traffic can sometimes reduce noise problems. For example, trucks can be prohibited from certain streets and roads, or they can be permitted to use certain streets and roads only during daylight hours. Traffic lights can be changed to smooth out the flow of traffic and to eliminate the need for frequent stops and starts. Speed limits can be reduced; however, about a 20 mile-per-hour reduction in speed is necessary for a noticeable decrease in noise levels (Ruckman, 2007). The present report is an effort at gauging the amount of noise reduction that will happen in reality if the transformation being done in Bradford City Center is completed. Experiment and Method Bradford city centre is undergoing its most significant transformation in nearly 50 years, taking Bradford forward as a city for the new millennium. Many 1960s buildings are being swept away to make room for the 1 billion regeneration program which includes the areas of Little Germany, Westgate, Centenary Square and Thornton Road. As a part of this program it is proposed to demolish the existing Police Headquarters and Court buildings located in the proximity of the Town Hall to make space for the Mirror Lake and surrounding park. The Bradford Council (Customer) has commissioned a provisional analysis of the current traffic noise levels and noise levels which are likely to exist after the demolition of these buildings and realignment of surrounding roads. The project involves in-situ noise measurements and CRTN calculations. These noise levels are mainly associated with the local traffic and commercial activities. A Street map of Bradford city centre and the area of the construction activities. The site work was carried out during the normal working hours (9am - 5pm). The selected locations were representative of the area with respect to the traffic flow volume, direction and composition. The sound level meters and high visibility jackets were fully checked before usage by a valid risk assessment. The noise level meter reading was adjusted to L10. The project involved in-situ noise measurements and CRTN calculations. It is anticipated that these noise levels are mainly associated with the local traffic and commercial activities. The team convened and went out to the sites where noise measurements were to be taken. Then, we got dressed in the yellow suits and the team was divided into two groups. Each group took 5 streets and started off. The readings were taken; the disturbing sound and noise measured by the sound device, from Mr. Barker, in the ten regions were taken according to the procedure followed in the Appendix. The readings were taken; light and heavy vehicles for each street were calculated. The streets were divided as segment 1 and segment 2. Corrective calculations were done for sound and noise processing in the appropriate methods as indicated in the tables that follow for each street. Data Analysis The data collected has been tabulated as below: Location Time (Hrs) Noise Level Traffic Composition Light Vehicles Heavy Vehicles Remarks 1 1520 74.65 394 21 2 1600 71.85 345 14 3 1630 76.18 742 32 4 1700 79.35 997 22 5 1700 70 928 136 6 1730 78.63 1334 34 7 1800 72.56 546 68 8 1600 69 728 69 9 1540 74 686 123 10 1520 74 880 186 Location Total Vehicles/Hour Heavy Vehicles/Hour Total Vehicles/18 Hour Percentage of Heavy Vehicles Remarks 1 Chester Street- Mor'ly Street (394+21)*3 = 1245 21*3 22410 5 p=100f/q 2 Chester Street- Little Horton St 1077 42 19386 4 3 Manchester St- Croft St 2322 96 41796 4 4 Croft St 3057 66 55026 2 5 Croft St- Wakfield Road 3192 408 57456 13 6 Leads Road 4104 102 73872 2 7 Bridge Street 1812 204 33156 7 8 Sunbridge Road 2391 207 43038 9 9 Market Street 2427 369 43686 15 10 Prince's Way 3198 558 57564 21 Conclusions and Recommendations By result of the survey or experiments conducted it was observed that some places still existed were the effects of the transformation were not complete. For such locations it is suggested that some other alternate arrangements like barriers, usage of insulators for windows etc. be used to reduce noise. Some other possibilities are the restriction of heavy vehicles during rush hours, pavements, usage of cycles and the public transport. Usage of public transport will prevent lots of noise and even traffic congestions and prevent accidents too. Strict observation of traffic rules will also help avoid much congestion. Encouraging the use of public transport by the government is a very valuable solution. Usage of cycles and even walking is both advantageous to the commuter's health and also the environment when moving short distances. Some more passive methods of noise reduction were discussed in the review. Active noise control is another method that can be used internally in the engines of the vehicles to reduce the noise levels. Appendix 1. The team met at 9:00 to discuss the role of the site survey. 2. The team agreed to schedule the meeting every Wednesday and Monday until all site requirements were completed. 3. Developing activity program. 4. Team carried out risk assessment and got it proven by Mr.Barker. 5. A site survey was cared out to identify the traffic noise measurement location and traffic volume composition location. 6. The team marked the above locations on the city map. 7. The team also agreed to split into two teams to conduct the actual survey. 8. Four equations was developed and agreed, to ask the Bradford counsel during their visit to the University on the 2nd of March. 9. The identified locations were agreed to by the professor. 10. We proceeded as previously decided and split into two groups as below. GROUP: A NAME SURVEY LOCATION TIME FOR EACH POINT ABDUL AZIZ 1, 2, 3, 4, 5 20 MINUTES ABDULLAH YASSER GROUP: B NAME SURVEY LOCATION TIME FOR EACH POINT MUSALUM 6, 7, 8, 9, 10 20 MINUTES NASER SAEED Reference Bruel & Kjaer (2007).Intensity Measurements in Building Acoustics. Retrieved April 18th from http://www.bksv.com/pdf/Measurements_in_Building_Acoustics.pdf Chris Ruckman (2007). Active Noise Control FAQ. Retrieved April 18th from: http://www.chrisruckman.com/ancfaq.htm FHWA. Highway Traffic Noise. Retrieved April 17th from: http://www.fhwa.dot.gov/environment/htnoise.htm Stephen Kelleher (1995). An appraisal of prediction techniques and assessment methods for noise and air pollution resulting from highway proposals. Retrieved April 17th from: http://users.aber.ac.uk/zwk/distlearn/virtlib/projects/kelleher/kelleher.html Wikipedia. Noise Pollution. Retrieved April 17th from: http://en.wikipedia.org/wiki/Noise_pollution Read More