FINAL REPORT. On Project Supplemental Guidance on the Application of FHWA s Traffic Noise Model (TNM)

Transcription

1 FINAL REPORT On Project Supplemental Guidance on the Application of FHWA s Traffic Noise Model (TNM) APPENDIX A Structure Reflected Noise and Expansion Joint Noise Prepared for: National Cooperative Highway Research Program (NCHRP) Transportation Research Board of The National Academies March 2014 HMMH Report No Prepared by: Research Topic Lead Environmental Acoustics in association with Bowlby & Associates, Inc. Grant S. Anderson Douglas E. Barrett

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3 Contents... A-1 A.1 Introduction... A-1 A.2 Modeling Techniques Evaluated... A-1 A.2.1 Candidate Modeling Technique #1: FHWA TNM modeling of reflected noise by developing image receptors... A-2 A.2.2 Candidate Modeling Technique #2: Using noise measurement data to develop combined structure-related predicted noise levels... A-7 A.2.3 Candidate Modeling Technique #3: Isolating individual components of structure-radiated noise using noise measurements... A-17 A.3 Applicable use conditions and limitations related to each best modeling practice... A-20 A.3.1 Best Modeling Practice #1A: FHWA TNM modeling of reflected noise by developing image receptors A-20 A.3.2 Best Modeling Practice #1B: Comparing noise measurements at a site containing reflections with one without reflections... A-20 A.3.3 Best Modeling Practice #2: Using noise measurement data to develop combined structurerelated predicted noise levels... A-21 A.3.4 Best Modeling Practice #3: Using a combination of Best Modeling Practices... A-22 A.4 Analyses at Schiller Street Location, Philadelphia, PA... A-22 A.4.1 Introduction... A-22 A.4.2 Summary of Noise and Traffic Data... A-23 A.5 Analyses of I-95 Section GIR Projects, Philadelphia, PA... A-33 A.5.1 Introduction... A-33 A.5.2 Summary of Noise and Traffic Data... A-33 A.6 Analysis of PA Turnpike Susquehanna River Bridge Project... A-44 A.6.1 Introduction... A-44 A.6.2 Summary of Noise and Traffic Data... A-44 A.7 Analyses of Bowlby Projects... A-49 A.7.1 Introduction... A-49 A.7.2 Summary of Noise and Traffic Data... A-49 A.8 Analysis of WSDOT I-5 Ship Canal Bridge Project... A-56 A.8.1 Introduction... A-56 A.8.2 Summary of Noise and Traffic Data... A-56 iii

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5 Appendix A Structure Reflected Noise and Expansion Joint Noise A.1 Introduction When modeling noise levels at receptors located adjacent to an elevated roadway on a structure (bridge or viaduct), FHWA TNM is capable of predicting the noise generated by the vehicles traveling on the highway structure, taking into account direct noise paths and diffracted noise influences of any noise blocking features (parapets, noise barriers, etc.). However, FHWA TNM Version 2.5 does not enable the direct modeling of noise reflected off of barriers or retaining walls on the opposite side of the roadway nor off of the underside of the structure itself. While Version 3.0 of FHWA TNM will be capable of modeling reflected noise, the treatment of such reflections will be limited to vertical or near vertical surfaces such as far-side barriers and retaining walls. It will not be appropriate for horizontal surfaces such as the underside of bridges and viaducts. In addition to the noise that can be reflected off of the underside of structures, vehicles traveling on a bridge create vibrations of the structure and these vibrations result in noise being radiated from/by the bridge superstructure. Vehicles traveling over bridge expansion joints also create noise that can travel to adjacent receivers located both above and below the elevation of the structure roadway as well as to receivers directly underneath the structure. In the majority of instances, the above listed structure-related noise conditions occur simultaneously, and their individual noise level contributions are not always able to be segregated. Therefore, the team has evaluated several candidate modeling techniques identified in its Draft Interim Report and considered the conditions identified above both individually and in combination. Based on these evaluations, several best modeling practices for the development of adjustments to the basic FHWA TNM predictions have been developed to account for these un-modeled structure-related (structure-reflected and structureradiated) noise conditions. It is envisioned that such practices will be applied similarly to the basic (modeled) noise level values generated by either FHWA TNM Version 2.5 or FHWA TNM Version 3.0. A.2 Modeling Techniques Evaluated Task 1 (Structure-Reflected Noise) candidate modeling techniques evaluated by the team primarily focused on developing best modeling practices to address noise reflected from the underside of bridge structures to adjacent receivers located below (lower in elevation) elevated portions of a highway. Sound paths to adjacent receivers located level with or above a highway are generally influenced by reflections off of the pavement which are inherently accounted for, at least in some degree, in the emission levels in the FHWA TNM. The evaluations of noise reflections off of roadway features such as safety barriers, median barriers, and retaining walls are discussed in Task Area 6. For these above-road receivers, structure-radiated noise is not believed to be a major issue since it is masked by direct path vehicle noise (predicted by FHWA TNM) and tire-pavement interaction variations (not a part of this research project). However, in certain situations, receivers located above the roadway are influenced by noise from expansion joints. The techniques developed to address the requirements of Task 2 (Expansion Joint Noise) for receivers located below the elevation of the highway were also evaluated for application at elevated receivers. A-1

6 A.2.1 Candidate Modeling Technique #1: FHWA TNM modeling of reflected noise by developing image receptors An image-source technique that constructs an image of any receptor influenced by noise reflecting off of the undersides of structures was evaluated and tested for several projects. An excellent description of this technique can be found in the Reiter/Bowlby paper titled Using the FHWA Traffic Noise Model (FHWA TNM) to Assess Noise Reflections Off Of the Underside of Elevated Bridge Structures, which can be found at This technique starts by using FHWA TNM skew section views to help identify which sections of roadways and which vehicle types are involved in the reflections that reach any particular receptor. For any receptor affected by noise reflections, its associated reflection-contributing sources are then modeled at that receptor s image location. For each affected receptor, its noise level from reflected sources is then added to the noise level generated in the base FHWA TNM run to obtain its total noise level. It is important to note that this technique only addresses reflected noise and does not account for the effects of structure-radiated noise or expansion joint noise. The direct path of noise from the noise source to the receptor can be modeled by the FHWA TNM. Figure from Reiter/Bowlby Paper This technique was utilized as a screening process by Reiter and Bowlby during the noise evaluation of a Tennessee Department of Transportation (TDOT) project that involved the proposed widening of Interstate 40 (I-40) and a proposed four-level interchange reconstruction in Nashville. The reflecting structure was a ramp with relatively low traffic volumes, so structure-radiated and joint noise was not a concern. First row measurement site locations from this screening process are indicated as sites 1, 2, and 3 in Figure 1. A-2

7 Figure 1 Tennessee DOT I-40 analysis locations in Nashville, TN Imagery 2014 Google Since the time that the screening analysis was completed, the project has been constructed. The team (through Bowlby and with TDOT concurrence) tested and evaluated this technique by conducting limited simultaneous measurements at three sites that were identified as being affected by reflected noise. These sites are labeled A, B, and C in Figure 1, with the area also shown in Figure 2. For comparison, simultaneous measurements were also taken at three additional sites (Sites D, E, and F in Figure 1) where traffic characteristics are similar, but where the elevated ramp structure is not present and where reflected noise is not an issue. A plan view and cross section view of Sites D and E are shown in Figure 3. The reflected noise component estimated by the screening analysis modeling was compared to the estimated reflective noise component derived from the comparative noise measurement process. Results are indicated in Table 1. While the measurements indicated a wider variation of the reflective noise values (3 to 8 db range) than the 4 to 5 db range estimated via the screening process, the average value was approximately 5 db via both methods. This indicated that either methodology (image source modeling or comparative measurements) appears to represent a viable Best Modeling Practice for estimating the contribution of structure-reflected noise. Figure 2 View in vicinity of Receptors A, B, and C Imagery 2014 Google A-3

8 Figure 3 View in vicinity of Receptors D and E Imagery 2014 Google Table 1 Comparison of screening analysis and noise measurements, I-40 Project in Nashville, TN A technique based on the Reiter/Bowlby technique was also used by Environmental Acoustics (EA) in its noise analysis for the widening and reconstruction of the I-95 Section GIR project in Philadelphia, PA. Three locations were influenced by noise from a parallel local roadway reflecting off of the underside of the I-95 viaduct structure towards residences in the community. At these locations, structure-radiated noise contributions (from deck and expansion joints) also affected noise levels at receptors close to the viaduct. One such location is shown in Figure 4. A-4

9 Source: Environmental Acoustics Figure 4 Noise from I-95 Viaduct affects homes on right. Homes also affected by noise from vehicles on far left local road that reflects off of underside of structure. Table 2 summarizes the effects of reflected noise at these locations, while the combined structure-related effects (deck noise, joint noise, and reflected noise) are addressed in the discussions contained in Candidate Modeling Technique #2 section. A-5

10 Table 2 Effects of reflected noise for I-95 Project in Philadelphia, PA Drip Edge Receptors at 5' Above Ground At 50 feet from Drip Edge (53 feet for Susquehanna, 43 feet for Cambria) At 100 feet from Drip Edge (123 feet for Susquehanna, 88 feet for Cambria) Location and Measurement Date A B C D E A B D E F A B D E F Measured Noise Level Modeled Noise Level without Structure- Related Noise Modeled Structure- Reflective Noise Contribution Modeled Noise Level with Reflections but without Structure- Radiated Noise = B plus C Effect of Reflections = D minus B Measured Noise Level Modeled Noise Level without Structure- Related Noise Modeled Structure- Reflective Noise Contribution Modeled Noise Level with Reflections but without Structure- Radiated Noise = B + D Effect of Reflections = E minus B Measured Noise Level Modeled Noise Level without Structure- Related Noise Modeled Structure- Reflective Noise Contribution Modeled Noise Level with Reflections but without Structure- Radiated Noise = B + D Effect of Reflections = E minus B I-95 GIR Sergeant Street, 9/21/ I-95 GIR Susquehanna Avenue, 9/20/ I-95 GIR Susquehanna Avenue, 9/20/10 db I-95 GIR Cambria Street, 9/21/ NOTE: All noise leves are Leq in db(a) A-6

11 A technique based on the Reiter/Bowlby technique was also used by the Washington State Department of Transportation (WSDOT) to evaluate the effects of noise reflections to communities adjacent to the twolevel bridge carrying Interstate 5 over the Ship Canal in Seattle. This evaluation is reported in WSDOT s 2005 publication titled I-5 Ship Canal Bridge Noise Study. Further discussion of this is technique is contained in Candidate Modeling Technique #2 section. A.2.2 Candidate Modeling Technique #2: Using noise measurement data to develop combined structure-related predicted noise levels Development of a best modeling practice that relies on noise measurements to establish adjustment factors associated with structure-related noise to apply to basic FHWA TNM values involved a multi-step approach. This approach was a refinement of an approach used by EA during its 2011 noise analysis of an adjacent section of I-95. For this current approach, EA initially conducted noise measurements directly underneath a span of the I- 95 viaduct at Schiller Street in Philadelphia (depicted in Figure 5) where other highway noise sources do not exist. Imagery 2014 Google Figure 5 Measurement locations under I-95 deck in vicinity of Schiller Street in Philadelphia, PA Three sets of simultaneous measurements were taken underneath the viaduct at three positions indicated in Figure 5: Site 1: Within five (5) feet of the bottom of the deck near an expansion joint Site 2: Within five (5) feet of the bottom of the deck at a point midway between expansion joints Site 3: At five (5) feet above the ground at a location midway between Positions 1 and 2 These measurements were performed using similar ANSI Type I noise meters and compatible microphone cables. Commonly available and relatively inexpensive equipment (connected pieces of halfinch electrical conduit costing less than $25.00 supported by speaker stands) was used to position the microphones at locations close to the underneath of the viaduct superstructure, as shown in Figure 6. Results of these measurements are included in Table 3. A-7

12 Table 3 Structure-radiated and expansion joint noise under I-95 Source: Environmental Acoustics Figure 6 Measurements of deck and expansion joint noise under I-95 near Schiller Street Figure 7 Input Parameters The measurements show very little difference in noise levels at positions underneath the structure, illustrating that, at this location, ground-level noise levels resulted from a combination of joint and deck noise, with neither of these noise sources predominating. In addition, there was little difference between noise levels measured just below the deck with those levels measured five feet above the ground. Based on these observations, it was assumed that a measurement taken at a point below the outside of the viaduct (drip edge location) would represent the combined noise level due to deck and joint noise at that location. To estimate the combined contribution of deck and joint noise at points at various distances (set-back locations) from the structure, drop off formulae associated with various drop off rates were developed. For the purpose of establishing an initial reference distance for calculating structure-related noise at set-back locations, it was assumed that the source of the noise emanates from the underside of the deck at the centerline of the structure, midway between the drip edges. In establishing structure-related noise levels at setback locations, the location of drip point noise was assumed to be mid-point between the bottom of the bridge deck and the ground. The input parameters described in the following procedure and A-8

13 illustrated in Figure 7 were used to determine the reference distance (D ref ), the distance from the assumed midpoint source of structure-related noise (S) to the drip edge location (A ref ). Measure the height of the structure, from the underside of the deck to the ground (h). Divide the distance by two (h/2) to calculate the midpoint between the ground and the underside of the deck. This is designated the drip-edge midpoint (A ref ). Measure the width of the structure from drip edge to drip edge (w). Divide the distance by two (w/2) to calculate the midpoint or centerline of the structure (M w ). The underside of the deck at M w is the assumed location of the source of the structure-related noise (S). To calculate D ref, the distance from the source of the deck noise (S) to the drip-edge midpoint A ref, the formula D ref = ( ) ( ) was employed. Figure 8 illustrates the relationship between D ref and the location of the analysis points at various setback distances from the drip edge. The height, width, and measured noise level at the drip edge of the structure are entered into the Structure-Related Noise Calculation Worksheet (Table 4). The spreadsheet calculates A ref, M w (or S), and D ref. Setback distances from the drip edge of the structure are included in Table 4 for standard distances of 25, 50, 100, 200 and 400 ft. A blank row (A xxx ) is provided for inserting an additional setback distance if desired. The spreadsheet also calculates the structure-related noise at the analysis points based on the three drop-off rates of 3.0, 4.5, and 6.0 db per double distance (db/dd) using the following formula: L Ax = L DE 10 Log 10 (D AP /D Ref ), where: L DE = L eq noise measurement in db(a) taken at 5 feet above ground under structure drip edge L Ax = Calculated structure-related noise level at an analysis point A x, located x feet from the drip edge D AP = point S to the analysis point A x D Ref = point S to Point A Ref The value of 10 in the formula represents a drop-off rate of 3 decibels per doubling of distance (db/dd). For the 4.5 db/dd calculation, this value is 15 in the formula. For a 6 db/dd drop-off rate, the value in the formula is 20. A-9

14 Figure 8 The relationship between D ref and the location of the analysis points A-10

15 Table 4 Structure-Related Noise Calculation Worksheet Structure-Related Noise Calculation Worksheet PennDOT I-95 at Shiller Street 4/16/ :11am Northbound Side at 25 feet and 50 feet Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 66.0 Set-back Calculations: S to = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX Clicking on the version of the spreadsheet in this report will bring up the Excel worksheet which may be copied for use. To test the appropriateness of this methodology, it was compared to setback measurements conducted at locations related to the following projects: 1. I-95 Section AFC at Schiller Street (9 sets of measurements at Schiller Street) at locations shown in Figure 9, and illustrated in Figures 10 and 11.. A-11

16 Imagery 2014 Google Figure 9 25 and 100 Setback Locations Source: Environmental Acoustics Figure 10 Schiller Street Drip Edge Measurement Locations Source: Environmental Acoustics Figure 11 Schiller Street 25 and 50 Setback Locations 2. Five (5) sets of measurements taken within I-95 Section GIR at Eyre Street, Sergeant Street, Susquehanna Avenue (two sets of measurements), and Cambria Street 3. Pennsylvania Turnpike Susquehanna River Bridge project in Highspire, PA (4 sets of measurements) taken at locations shown in Figure 12, and illustrated in Figures 13, 14, and 15. Imagery 2014 Google Figure 12 Measurement Sites adjacent to PA Turnpike Susquehanna River Bridge Source: Environmental Acoustics Figure 13 Measurements Under Deck and at 25 and 50 Setbacks adjacent to PA Turnpike Susquehanna Bridge Figure 14 Measurements adjacent to PA Turnpike Susquehanna River Bridge Source: Environmental Acoustics Figure 15 Measurements under deck and above bridge rail at PA Turnpike Susquehanna River Bridge 4. Indiana DOT project (2 sets of measurements) at all receptors indicated by red circles in Figure

17 Source: Bowlby & Associates, Inc., Imagery 2014 Google Figure 16 Structure-related measurements for Indiana DOT Project Southbound Locations (Blue Circles on Left) and Northbound Locations (Red Circles on Right) 5. Arkansas I-40 (2 sets of measurements) at sites shown in Figure 17, and illustrated in Figure 18. Source: Bowlby & Associates, Inc., Imagery 2014 Google Figure 17 Arkansas DOT I-40 Project Measurement Locations Source: Bowlby & Associates, Inc. Figure 18 Arkansas DOT I-40 measurements locations near expansion joint at drip edge and at 53 from drip edge The results of these tests are summarized in Table 5, which displays average values for all measurement sets conducted for each listed project. A-13

18 Table 5 Tests of Worksheet drop-off rate methodology Date Measurement Period Location of Measurement in Relationship to Drip Edge Measured Leq Noise Level FHWA TNM Modeled L eq (h) Noise Level due to Highway Traffic Only Assumed Effect of Structure- Related Noise Modeled L eq (h) Noise Level Assuming Spreadsheet Value Adjustment for Structure-Related Noise and Assuming Drop-Off Rate of: Measured Minus Modeled L eq Noise Level Assuming Drop-Off Rate of: 3 db/dd 4.5 db/dd 6 db/dd 3 db/dd 4.5 db/dd 6 db/dd From To feet db(a) db(a) db db(a) db(a) db(a) db(a) db(a) db(a) At Drip Edge I-95 Projects in Philadelphia, PA, 2010 and 2013; Combined deck, joint, and some locations with reflected noise Pennsylvania Turnpike Bridge over Susquehanna River, 4/17.13; Segmental Concrete (Insignificant deck noise; noise from expansion joint); Noise assumed to drop off from point 3 feet below bottom of deck Inside of Drip Edge At Drip Edge Indiana DOT Project, 7/14/10; H = 90 feet At Drip Edge Arkansas DOT Project, 2008; H = 17 feet; Noise source dropoff from joint A-14

19 In evaluating the Pennsylvania Turnpike Susquehanna River Bridge project, field observations and monitoring confirmed that there was little, if any, noise radiated by the deck. However, noise from a near-by expansion joint was noticeable. For this reason, two additional sets of measurements were taken to assess the expansion joint contribution to noise levels at the 25-foot and 50- foot setback locations. These contributions were established by taking a noise measurement near the joint (see Figure 19) and then applying the worksheet drop-off methodology. These contributions are the structure-related contributions used to calculate the Table 5 modeled noise levels for this project. Source: Environmental Acoustics Drip edge measurements for the Arkansas DOT I- Figure 19 Measurement of expansion joint 40 project were taken near the expansion joint noise at PA Turnpike Susquehanna River Bridge (see Figure 18) which produced noticeable (and probably predominant) structure-related noise. For this situation, better worksheet methodology correlation with setback measurements was obtained by assuming that the noise source emanated from the joint above the measurement point rather than at the midpoint of the structure. While WSDOT applied the Reiter/Bowlby technique to adjust FHWA TNM modeled noise levels to account for structure-reflected noise on the two-level Ship Canal Bridge in Seattle, WA, the abovediscussed drop-off methodology was applied to several selected sites shown in Figure 20 to determine its potential applicability to account for structure-related noise effects for such a project. A comparison of the two methodologies is presented in Table 6. This comparison indicates that with the worksheet methodology and a line source drop of rate of 3 db per double-distance, similar values were obtained compared to those using the Reiter/Bowlby methodology. The selection of the appropriate methodology for a project such as this would most likely depend upon whether the structure-related noise is associated with reflections, deck radiated noise, expansion joint noise or some combination of these sources. Where reflected noise is the predominant source, the Reiter/Bowlby technique is probably most appropriate, while the worksheet methodology could be considered where all sources are present, but where deck and/or joint noise sources predominate. A-15

20 Imagery 2014 Google Figure 20 Measurement and receptor sites adjacent to I-5 Ship Canal Bridge Table 6 Comparison of methodologies for WSDOT Ship Canal Bridge project The WSDOT report titled Expansion Joint Noise Reduction on the New Tacoma Narrows Bridge describes methods used to mitigate noise from large finger-type expansion joints constructed as part of A-16

21 the new bridge near Tacoma. While expansion joint noise was the major factor of annoying noise effects expressed by the adjacent residences to WSDOT, other factors such as reflections and deck vibrationgenerated noise were also observed. Some of the complaining residents were located in dwellings that were on ground that was elevated with respect to the bridge. Due to traffic noise, obtaining valid noise measurements of expansion joints or the deck radiated noise itself from a point above the roadway elevation is not possible. This was confirmed by EA in its measurements above the outside barrier on the PA Turnpike Bridge. However, measurements of deck and joint noise below the structure at the drip edge could be taken and extrapolated to distant receptors using the worksheet methodology. While no traffic data was collected simultaneously with the noise measurements and no modeling was performed, qualitative conclusions regarding the sound content and mitigation effectiveness were made by WSDOT based on the one-third octave band noise measurements. A.2.3 Candidate Modeling Technique #3: Isolating individual components of structureradiated noise using noise measurements This technique was identified by the team in it Draft Interim Report for consideration in areas noticeably affected by more than one component of structure-radiated noise. The procedures identified in the Draft Interim Report were performed in the evaluation of Candidate Modeling Techniques #1 and #2, addressed above. In this development, practices were identified to address both the individual and combined effects of structure-reflected noise, deck-radiated noise, and expansion joint noise. A Additional Considerations During its evaluation of candidate modeling practices, the team conducted a review of the frequency distribution curves for the evaluated projects. This review focused more on the comparison of the shape of the curves than on a comparison of the L eq values. This review indicated that as structure-related noise became less predominant (as distance from the drip edge increases) the spikes that occur at closer distances flatten out and/or disappear. This is particularly noticeable at the lower frequencies. Although the peaks do not always occur at the same frequencies for each project, the flattening out is evident for each project, as demonstrated by the graphs in Figures 21 through 24. It is assumed that the uniqueness of each project in terms of the exact shape of the curves is a function of many variables, such as structure type, structure height, degree of influence of deck and joint noise, etc. However, the charts do provide a degree of verification in that the flattening out of the lower frequency spikes appear to correlate to the setback locations where structure-related noise effects are minimized or non-existent. Thus, review of frequency curves can provide additional verification of the extent or limits of structure-related noise contributions. A-17

22 Noise Level, Leq (dba) Noise Level, Leq (dba) I-95, Schiller Street Energy Average of Noise Measurements Deck,Leq = 65.5 dba Ground, Leq = ft, Leq = 66.9 dba 50 ft, Leq = 67.1 dba ft, Leq = 65.3 dba Hz 16 Hz 20 Hz 25 Hz 31.5 Hz 40 Hz 50 Hz 63 Hz 80 Hz 100 Hz 125 Hz 160 Hz 200 Hz 250 Hz 315 Hz 400 Hz 500 Hz 630 Hz 800 Hz 1 khz khz 2 khz 2.5 khz 3.15 khz khz Frequency, Hz (1/3 Octave Band) 4 khz 5 khz 6.3 khz 8 khz 10 khz 12.5 khz Figure 21 I-40 Arkansas Project Under Drip Edge,Leq = 80.7 dba 20.0 At Yield Sign, Leq = 69.6 dba 1719 W. 35th, Leq = 68.8 dba Hz 31.5Hz 40Hz 50Hz 63Hz 80Hz 100Hz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz 500Hz 630Hz 800Hz 1kHz 1.25kHz 1.6kHz 2kHz 2.5kHz 3.15kHz 4kHz 5kHz 6.3kHz 8kHz 10kHz Frequency, Hz (1/3 Octave Band) Figure 22 A-18

23 k 1.25 k 1.6 k 2 k 2.5 k 3.15 k 4 k 5 k 6.3 k 8 k 10 k 12.5 k Noise Level, Leq (dba) Noise Level, Leq (dba) 90 I-5 Ship Canal Bridge ft, Leq = 87.8 dba 25 ft, Leq = 79.6 dba 75 ft, Leq = 70.8 dba 125 ft, Leq = 67.3 dba ft, Leq = 68.5 dba 250 ft, Leq = 65.8 dba 225 ft, Leq = 62.8 dba 0 20Hz 25Hz 31.5Hz 40Hz 50Hz 63Hz 80Hz 100Hz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz 500Hz 630Hz 800Hz 1kHz 1.25kHz 1.6kHz 2kHz 2.5kHz 3.15kHz 4kHz 5kHz 6.3kHz 8kHz 10kHz 12.5kHz 16kHz 20kHz Frequency, Hz (1/3 Octave Band) Figure 23 CAMBRIA STREET 1/3 OCTAVE BAND LEQ NOISE LEVELS AT VARIOUS SETBACK DISTANCES Rion # 2 under deck Rion # drip edge Rion # 45' Rion # 95' 0 Frequency (Hz) 1/3 Octave Band Figure 24 A-19

24 A.3 Applicable use conditions and limitations related to each best modeling practice The team recognizes that any one of its best modeling practices may not be appropriate for all modeling scenarios. To the extent possible, limitations of each practice have been identified by the team, and are discussed below. It is important to note that the suggested best practices have been applied to actual projects containing a variety of traffic and geometric conditions. However, while the team believes that these practices provide a reasonable approach to determining structure-related noise level adjustments to FHWA TNM predictions of direct highway noise, it recognizes that these practices may not be appropriate for every project condition that could exist. The processes, applications, and limitations of the suggested best modeling procedures developed for structure-related noise adjustments to modeled FHWA TNM values are summarized below. A.3.1 Best Modeling Practice #1A: FHWA TNM modeling of reflected noise by developing image receptors Process: 1. Model direct highway noise contributions from all roadways using FHWA TNM. 2. Use Reiter/Bowlby technique to estimate adjustments due to reflections off of the underside of structures. 3. Apply adjustments to obtain structure noise-adjusted predicted noise level. Applications and Limitations: 1. Since this best modeling practice is solely based on noise modeling, it can be applied to any type of highway project, i.e. construction on new location or reconstruction of an existing highway 2. Use requires detailed geometric and traffic information. 3. Use does not account for the variation of reflected noise associated with different types of superstructures i.e., spread box beams, adjacent box beams, segmental bridges, steel I-beams, steel deck pans, etc. 4. Only deals with structure-reflected noise and does not account for any other structure-related noise. A.3.2 Best Modeling Practice #1B: Comparing noise measurements at a site containing reflections with one without reflections Process: 1. Model direct highway noise contributions from all roadways using FHWA TNM. Model for each traffic condition at all receptors associated with each measurement period. 2. Conduct multiple sets (minimum of three) of noise measurements at selected setback locations where reflective noise is believed to be a contributing factor. 3. Conduct multiple sets (minimum of three) of simultaneous measurements at locations with similar setbacks that have similar traffic and topographic features, but where reflections from the underside of a structure are not a contributing factor A-20

25 4. For each measurement setback distance, calculate the difference between the values for items 2 and 3, above. This is the reflective noise adjustment factor. 5. For each measurement setback distance, apply the item 4 reflected noise adjustment factor to the FHWA TNM value from Item 1 to obtain the structure noise-adjusted predicted noise level. Applications and Limitations: 1. Use requires detailed geometric and traffic information. 2. Inherently accounts for the type of superstructure. 3. Requires exclusion of extraneous noise sources. 4. Requires sufficient equipment and manpower to perform simultaneous measurements and to collect simultaneous traffic data. 5. Requires finding a non-reflective location that has similar traffic and topography for comparison with the reflective location. A.3.3 Best Modeling Practice #2: Using noise measurement data to develop combined structure-related predicted noise levels Process: 1. Model direct highway noise contributions from all roadways using FHWA TNM. Model under a variety of free-flow traffic conditions at all receptors associated with each measurement period. 2. Conduct multiple (minimum of three) sets of noise measurements at the drip edge ground level location and at a minimum of two (2) setback distances for purposes validating the FHWA TNM runs and determining the extent of structure-related noise contributions. If third-octave band measurements were conducted, review frequency graphs for setback locations to help verify the limits of structure-related noise contributions. 3. Apply the adjustments from the appropriate Structure-Related Noise Calculation Worksheet (see Table 4) to levels at setback locations to determine total modeled noise levels at each setback location. 4. If expansion joint noise is the predominant structure-related noise source, assume that the noise source emanates from the joint above the measurement point rather than at the midpoint of the structure, and adjust the Worksheet D ref value to be the distance from the drip edge microphone to the bottom of the structure s deck. 5. Apply the Worksheet values to FHWA TNM predicted levels for the proposed project using the drop-off rates that best correlate with the measured levels. Applications and Limitations: 1. Use requires detailed geometric and traffic information. 2. Inherently accounts for the type of superstructure 3. Requires exclusion of extraneous noise sources A-21

26 4. Requires sufficient equipment and manpower to perform simultaneous measurements and to collect simultaneous traffic data 5. Does not account for any reflected noise from other highway noise sources that affects setback locations unless such reflected noise reaches the ground-level drip edge location 6. This best modeling practice was developed based on actual existing conditions and tested against these conditions. As such it is likely to be most applicable to projects that involve reconstruction and or widening of existing highways as opposed to highways on new locations. In any case, measurements should be taken at structures that resemble the structure type and configuration that nearest replicates that planned for the proposed highway improvement project. 7. While measurements conducted during the development of the Worksheet did not indicate substantial variation of expansion joint and/or deck noise levels due to the variety of observed traffic conditions, users may want to test this methodology under different traffic conditions as well as test the characteristics of their project s specific structure type, employing techniques used by the team in developing the Worksheet drop-off methodology. A.3.4 Best Modeling Practice #3: Using a combination of Best Modeling Practices As illustrated in the testing of the various candidate modeling techniques, several of the projects evaluated were affected by structure-reflected noise contributions in addition to deck radiated and/or expansion joint noise contributions. This required the incorporation of both Best Modeling Practices #1A and #2. If appropriate, Best Modeling Practice #1B could also be employed in such a situation. In addition, there may be situations where two different practices may be considered for application. For example, while WSDOT used Best Modeling Practice #1A to adjust FHWA TNM modeled noise levels to account for structure-reflected noise on the two-level Ship Canal Bridge in Seattle, WA, EA applied Best Modeling Practice #2 to several selected setback receptors to determine its potential applicability to account for structure-related noise effects for such a project. This comparison indicated that both Best Modeling Practices produced similar values for the selected receptors. The selection of the appropriate methodology for a project such as this would most likely depend upon whether the structure-related noise is associated with reflections, deck radiated noise, expansion joint noise or some combination of these sources. Where reflected noise is the predominant source, Best Modeling Practice #1A is probably most appropriate, while Best Modeling Practice #2 could be considered where all sources are present, but where deck and /or joint noise sources predominate. A.4 Analyses at Schiller Street Location, Philadelphia, PA A.4.1 Introduction Measurements taken at the Schiller Street area of I-95 Section AFC in Philadelphia, PA provided the basis for the development of the drop-off calculation methodology contained in the Structure-Related Noise Calculation Worksheet and in the suggested Best Modeling Practice #2 described in the report. These measurements were compared to noise levels conducted using FHWA TNM to determine structurerelated noise contribution associated with deck-radiated and expansion joint noise. A-22

27 A.4.2 Summary of Noise and Traffic Data A summary of noise and traffic data associated with the analysis of structure-related noise in the Schiller Street area and the FHWA TNM data files are included on an accompanying CD-ROM that is on file at Environmental Acoustics. Tables 7 through 15 contain the associated Structure-Related Noise Calculation Worksheets for the Shiller Street area. A-23

28 Table 7 A-24

29 Table 8 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 66.3 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/ :33am Northbound Side at 25 feet and 50 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-25

30 Table 9 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 66.2 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/ :53am Northbound Side at 25 feet and 50 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-26

31 Table 10 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 65.7 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/ :13pm Northbound Side at 25 feet and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-27

32 Table 11 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 64.9 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/ :33pm Northbound Side at 25 feet and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-28

33 Table 12 A-29

34 Table 13 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 66.4 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/2013 2:26pm Northbound Side at 50 feet and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-30

35 Table 14 A-31

36 Table 15 Input Data: h: Height of structure, from ground to underside of deck 27 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 132 M w : Midpoint of structure (w/2) The underside of the deck at this 66 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 67, db(a) 66.2 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Schiller Street 4/16/2013 3:00pm Northbound Side at 50 feet and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-32

37 A.5 Analyses of I-95 Section GIR Projects, Philadelphia, PA A.5.1 Introduction The suggested Best Modeling Practice #2 described in the report was tested against FHWA TNM modeling and measurement data related to several I-95 Section GIR analysis locations. A.5.2 Summary of Noise and Traffic Data A summary of noise and traffic data associated with the analysis of structure-related noise for these I-95 Section GIR locations and the FHWA TNM data files are included on an accompanying CD-ROM that is on file at Environmental Acoustics. Tables 16 through 25 contain the associated Structure-Related Noise Calculation Worksheets for each analysis period evaluated for I-95 Section GIR sites. A-33

38 Table 16 Input Data: h: Height of structure, from ground to underside of deck 15 A ref : Center point between ground and underside of structure (h/2). 7.5 w: Width of structure 100 M w : Midpoint of structure (w/2) The underside of the deck at this 50 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 51, db(a) 73.2 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Eyre Street 9/21/2010 9:52am Southbound Side at 25 feet, 50 feet, and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-34

39 Table 17 Input Data: h: Height of structure, from ground to underside of deck 23 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 115 M w : Midpoint of structure (w/2) The underside of the deck at this 57.5 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 59, db(a) 73.6 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Sergeant Street 9/21/ :20am Southbound Side at 50 feet and 100 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-35

40 Table 18 Input Data: h: Height of structure, from ground to underside of deck 23 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 110 M w : Midpoint of structure (w/2) The underside of the deck at this 55 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 56, db(a) 70.6 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Susquehanna Avenue 9/20/2010 2:40pm Southbound Side at 53 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-36

41 Table 19 Input Data: h: Height of structure, from ground to underside of deck 23 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 110 M w : Midpoint of structure (w/2) The underside of the deck at this 55 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 56, db(a) 70.6 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Susquehanna Avenue 9/20/2010 2:40pm Southbound Side at 123 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-37

42 Table 20 Input Data: h: Height of structure, from ground to underside of deck 23 A ref : Center point between ground and underside of structure (h/2) w: Width of structure 110 M w : Midpoint of structure (w/2) The underside of the deck at this 55 point is the assumed source of structural noise (S). D ref : Reference distance - from S to A ref 56, db(a) 70.6 Set-back Calculations: Structure-Related Noise Calculation Worksheet PennDOT I-95 at Susquehanna Avenue 9/20/2010 2:40pm Southbound Side at 192 feet = 3.0 db/dd A ref A A A A A A XXX A ref A A A A A A XXX S to S to S to = 4.5 db/dd = 6.0 db/dd A ref A A A A A A XXX A-38