Highway Noise Issues

1. We use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Normal conversation takes place at 60 decibelsWe use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Normal conversation takes place at 60 decibels

3. Quantifying Noise Measuring Pavement Noise Mitigation Methods Comparison of Pvmt. Surfaces Arizona’s Quiet Pavements International Community is ahead of U.S. in terms of measuring, regulating and controlling noise. International Community is ahead of U.S. in terms of measuring, regulating and controlling noise.

4. We use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Normal conversation takes place at 60 decibelsWe use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Normal conversation takes place at 60 decibels

5. We use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Human hearing begins at a decibel level of 0. A whisper is approximately 20 decibels. Normal conversation occurs in the region of 50 to 60 decibels. Discomfort begins around 70 decibels. As an example, a vacuum cleaner produces on the order of 80 decibels. A chain saw produces about 100 decibels. Standing in front of speakers at a rock concert would give about 120. Irreversible ear damage occurs at 180 decibels. For highway noise, we can get up to 90 decibels.We use the Decibel Scale Sound pressure levels are used to measure the intensity of sound and are expressed in terms of decibels. The decibel scale is a logarithmic unit that expresses the ratio of the sound pressure level being measured to a standard reference level. Human hearing begins at a decibel level of 0. A whisper is approximately 20 decibels. Normal conversation occurs in the region of 50 to 60 decibels. Discomfort begins around 70 decibels. As an example, a vacuum cleaner produces on the order of 80 decibels. A chain saw produces about 100 decibels. Standing in front of speakers at a rock concert would give about 120. Irreversible ear damage occurs at 180 decibels. For highway noise, we can get up to 90 decibels.

6. First a few generalizations about sound and its propagation: The decibel scale can be deceptive because small changes in the decibel level are very noticeable. Increasing the decibel level by 10 is perceived by most people as doubling the noise. So 70 dB(A) is twice as loud as 60 dB(A), and 80 dB(A) is twice as loud as 70. Remember that conversation takes place at around 60 dB(A), a freight train moving @ 45mph produces 93dB(A), and a chainsaw gives off about 100 dB(A). If one is exposed to 80 dB(A) or more for eight hours over an extended amount of time, damage to hearing can occur. First a few generalizations about sound and its propagation: The decibel scale can be deceptive because small changes in the decibel level are very noticeable. Increasing the decibel level by 10 is perceived by most people as doubling the noise. So 70 dB(A) is twice as loud as 60 dB(A), and 80 dB(A) is twice as loud as 70. Remember that conversation takes place at around 60 dB(A), a freight train moving @ 45mph produces 93dB(A), and a chainsaw gives off about 100 dB(A). If one is exposed to 80 dB(A) or more for eight hours over an extended amount of time, damage to hearing can occur.

7. Next Because we are dealing with a logarithmic scale, two passing noise sources can not be merely added together. They must be converted back to sound pressure, Added, and then converted back. So two 75 decibel sources combine to produce 78 decibels.Next Because we are dealing with a logarithmic scale, two passing noise sources can not be merely added together. They must be converted back to sound pressure, Added, and then converted back. So two 75 decibel sources combine to produce 78 decibels.

8. Simply reducing the decibel level by 3 provides the same effect as doubling the distance between the source of the noise and the person hearing it. So, if a car passing 50 ft. away produces a noise level of 67 (Mouse click for sound waves and sound effects), and (Mouse click for next slide.)Simply reducing the decibel level by 3 provides the same effect as doubling the distance between the source of the noise and the person hearing it. So, if a car passing 50 ft. away produces a noise level of 67 (Mouse click for sound waves and sound effects), and (Mouse click for next slide.)

9. if by changing the road surface we can lower the noise to 64 dB(A), it would amount to the same as moving the person to 100 ft. away. (Mouse click for sound waves and sound effects) if by changing the road surface we can lower the noise to 64 dB(A), it would amount to the same as moving the person to 100 ft. away. (Mouse click for sound waves and sound effects)

10. A 3dB(A) reduction corresponds to: doubling the distance reducing traffic volume by 50% reducing traffic speed by 25%

11. FHWA - Noise Abatement Criteria is 67 dB(A) “this is not an absolute value or design standard, only a level where noise mitigation must be considered” Noise mitigation can only be considered when a project is new or reconstructed to add additional capacity. In other words only during major new construction or reconstruction. Current policy does not consider pavement type in the prediction of highway noise levels. FHWA - Noise Abatement Criteria is 67 dB(A) “this is not an absolute value or design standard, only a level where noise mitigation must be considered” Noise mitigation can only be considered when a project is new or reconstructed to add additional capacity. In other words only during major new construction or reconstruction. Current policy does not consider pavement type in the prediction of highway noise levels.

12. Side-Line Measurements Statistical By-pass Method (ISO 11819-1)

13. Close-proximity (CPX) Method In Europe, they use the Close-Proximity Method (CPX) designated - ISO/CD 11819-2 to measure noise generated by the tire pavement interaction. This method uses very sensitive microphones mounted close to standardized tires near the pavement surface to record the sound pressure levels produced as the test trailer or vehicle moves along the road.In Europe, they use the Close-Proximity Method (CPX) designated - ISO/CD 11819-2 to measure noise generated by the tire pavement interaction. This method uses very sensitive microphones mounted close to standardized tires near the pavement surface to record the sound pressure levels produced as the test trailer or vehicle moves along the road.

15. Comparison of CPX versus Side-Line MeasurementsIndianapolis - September 2003

16. What Can Be Done to Mitigate Pavement Noise? Distance Obstructions Noise Walls Earth Berms Trees/ Shrubs Control at the Source with Pavement Surface

17. Controlled Through Distance For every doubling of the distance the rule of thumb is that the noise is reduced 3dBA. What we are seeing in our test results is that this is closer to 4.5 to 6 dBA for each doubling of the distance. So much for rules of thumb.For every doubling of the distance the rule of thumb is that the noise is reduced 3dBA. What we are seeing in our test results is that this is closer to 4.5 to 6 dBA for each doubling of the distance. So much for rules of thumb.

18. Controlled Through ObstructionsAverage 1 dBA for each 2 ft of Wall Above Line of Sight The important message is that the line of site has to be broken. Once it is broken there is a 5 dBA reduction. If the line of sight is not broken the mitigation is not effective. So if you can see the noise source, don’t believe the noise mitigation strategy unless it is sheer distance. The other rule of thumb is that once the line of sight has been broken, for each additional 2 ft of wall height the there is a 1 dBA reduction in noise. So the 4 dBA credit we are taking represents about 8 ft in additional wall height.The important message is that the line of site has to be broken. Once it is broken there is a 5 dBA reduction. If the line of sight is not broken the mitigation is not effective. So if you can see the noise source, don’t believe the noise mitigation strategy unless it is sheer distance. The other rule of thumb is that once the line of sight has been broken, for each additional 2 ft of wall height the there is a 1 dBA reduction in noise. So the 4 dBA credit we are taking represents about 8 ft in additional wall height.

19. Noise Walls One way to combat noise in residential areas is to construct noise barriers along busy roadways. These can range from earthen beams to wooden or block walls. For the first row of residences immediately in the shadow of the barrier, a 10 d-B(A) reduction is possible. However, The walls must be high enough and long enough to be effective, meaning that houses and tall buildings that are still in the line of sight of the roadway will not benefit from the construction of the wall. Barriers placed on opposite sides of a roadway can cause Refraction of the noise that can reduce the efficiency of both Barriers by as much as half (5dB(A) versus 10 dB(A). One way to combat noise in residential areas is to construct noise barriers along busy roadways. These can range from earthen beams to wooden or block walls. For the first row of residences immediately in the shadow of the barrier, a 10 d-B(A) reduction is possible. However, The walls must be high enough and long enough to be effective, meaning that houses and tall buildings that are still in the line of sight of the roadway will not benefit from the construction of the wall. Barriers placed on opposite sides of a roadway can cause Refraction of the noise that can reduce the efficiency of both Barriers by as much as half (5dB(A) versus 10 dB(A).

21. Walls top 10 States in 1998 spent over $1.3M per mile do nothing to eliminate the noise at the source Earth Berms require a lot of land if very high Vegetation takes a long time to develop 200’ thick would only achieve a 10 dB reduction Noise Barrier Effectiveness Must Justify Expense Effectiveness must justify expense. The top 10 wall building States in 1998(last figures that were published) spent over $1.3 million per mile of Barrier Wall which added nothing to the pavement or its longevity. Earth Berms require a lot of land if very high Noise walls often detract from the appearance of a given area, and this may lower property values. Green Walls of Vegetation would need to be over 200 Feet thick to achieve a mere 10 dB reduction. Walls do nothing to eliminate the noise at the source, or to improve the outdoor environment. Effectiveness must justify expense. The top 10 wall building States in 1998(last figures that were published) spent over $1.3 million per mile of Barrier Wall which added nothing to the pavement or its longevity. Earth Berms require a lot of land if very high Noise walls often detract from the appearance of a given area, and this may lower property values. Green Walls of Vegetation would need to be over 200 Feet thick to achieve a mere 10 dB reduction. Walls do nothing to eliminate the noise at the source, or to improve the outdoor environment.

22. Controlling At the Source Autos principally generate noise from their tires. Trucks generate their noise emissions from the three locations shown. The stack (eg exhaust) is particularly important because of its higher projection point and this makes mitigation more difficult. An important point to make here is that the noise issues we are generally confronted with on the Phoenix network are auto generated noised from the tires. That is the principal culprit. At locations with high percentages of truck traffic different measures may or may be necessary. Autos principally generate noise from their tires. Trucks generate their noise emissions from the three locations shown. The stack (eg exhaust) is particularly important because of its higher projection point and this makes mitigation more difficult. An important point to make here is that the noise issues we are generally confronted with on the Phoenix network are auto generated noised from the tires. That is the principal culprit. At locations with high percentages of truck traffic different measures may or may be necessary.

23. Back in the US, we have a long way to go to catch up. While Pavement/tire noise has been studied for well over 30 years in this country, NCHRP Synthesis 268 is the latest summary of the research findings was published in 1998 and was based on research done prior to 1997. Back in the US, we have a long way to go to catch up. While Pavement/tire noise has been studied for well over 30 years in this country, NCHRP Synthesis 268 is the latest summary of the research findings was published in 1998 and was based on research done prior to 1997.

27. OGFCs Reduce Noise, Eliminate Hydroplaning, Increase Wet Friction, and Minimize Spray

30. Is It Cost Effective? A decrease of 2 dB means a reduction of five feet in wall height or for a mile of pavement a reduction of $528,000 (Average of $20/sf)

31. OGFC is the quietest surface type. (Wayson, NCHRP Synthesis 268) SMA has also proven to be a quiet surface. (Wisconsin DOT, 1993) Dense graded HMA surfaces are quieter than PCC pavements. (Hibbs and Larson, Report FHWA-SA-96-068, May 1996) Summary: Effect of Pavement Surface While almost any type of asphalt pavement can reduce noise, the most effective is the open-graded friction course. Stone matrix asphalt pavements have also shown great potential for reducing tire noise through their coarse texture. Even the workhorse of HMA pavements, dense-graded mixtures, are generally quieter than concrete pavement surfaces. References Wayson, R.L., Relationship Between Pavement Surface Texture and Highway Traffic Noise, National Cooperative Highway Research Program, Synthesis No. 268, 1998. Wisconsin Department of Transportation, Effects of Pavement Surface Types on Sound Levels, I-43 SMA Pavement, Waukesha County, District 2 Environmental Unit, January 1993. Hibbs, B.O. and R.M. Larson, Tire Pavement Noise and Safety Performance, FHWA, Report No. FHWA-SA-96-068, May 1996. While almost any type of asphalt pavement can reduce noise, the most effective is the open-graded friction course. Stone matrix asphalt pavements have also shown great potential for reducing tire noise through their coarse texture. Even the workhorse of HMA pavements, dense-graded mixtures, are generally quieter than concrete pavement surfaces. References Wayson, R.L., Relationship Between Pavement Surface Texture and Highway Traffic Noise, National Cooperative Highway Research Program, Synthesis No. 268, 1998. Wisconsin Department of Transportation, Effects of Pavement Surface Types on Sound Levels, I-43 SMA Pavement, Waukesha County, District 2 Environmental Unit, January 1993. Hibbs, B.O. and R.M. Larson, Tire Pavement Noise and Safety Performance, FHWA, Report No. FHWA-SA-96-068, May 1996.

32. Arizona DOT Uses ARFC to Provide Quiet Pavements ADOT is Spending $34M to Overlay PCCP in the Phoenix Metropolitan The ARFC is Minus 9.5mm & 9-9.5% Binder 12.5 mm Thick When Used on Flexible Pavement 25 mm Thick When Used on PCCP ADOT Uses Pavement Type (ARFC) as a Noise Mitigation Strategy (4 dBA)

36. Highway noise very important to public Small changes in dB(A) level very noticeable reduction of 3dB(A) like doubling distance or halving traffic Sound barriers expensive and not very effective Controlling Noise at the Source is Best Option Dense HMA 2-4dB(A) quieter than PCC OGFCs 1-9dB(A) quieter than Dense HMA Summary When it comes to noise control, we can Build walls and berms … which are expensive and often not very effective Insulate buildings…which is expensive and impractical Or follow the leads of the Europeans and control noise at the sourceWhen it comes to noise control, we can Build walls and berms … which are expensive and often not very effective Insulate buildings…which is expensive and impractical Or follow the leads of the Europeans and control noise at the source