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From page 275... ... D-1 Erik Salomons, TNO Darlene Reiter and Rennie Williamson, Bowlby & Associates Roger Wayson, Wyle Ken Kaliski and Ryan Haac, RSG Aaron Hastings, Volpe A P P E N D I X D Modeling Read the entire page →
From page 276... ... D-2 Contents D-3 Chapter D-1 Introduction D-5 Chapter D-2 TNM, Comparison with Measurements D-11 Chapter D-3 Harmonoise, PE D-32 Chapter D-4 Conclusions D-33 References D-34 Annex A Loglin Sound Speed Profiles D-38 Annex B Linearization of Sound Speed Profiles Read the entire page →
From page 277... ... D-3 Calculation models for traffic noise are commonly based on a distinction between two physical phenomena: sound emission at the source and sound propagation from the source to the receiver. The sound level at the receiver is calculated in two steps (see Figure D-1) Read the entire page →
From page 278... ... D-4 How Weather Affects the Noise You Hear from Highways Harmonoise, however, is based on some approximations. An important approximation is that the sound speed profile in the atmosphere is linearized (i.e., a linear change in sound speed with elevation above ground) Read the entire page →
From page 279... ... D-5 The team modeled the No-Barrier and Barrier sites using the FHWA TNM 2.5 computer program and compared the measured sound levels to the TNM-predicted sound levels for neutral conditions. TNM Model The team modeled the No-Barrier and Barrier sites in TNM using assumptions that represented actual field and traffic conditions at the sites. Read the entire page →
From page 280... ... D-6 How Weather Affects the Noise You Hear from Highways The pavement at both sites is rubberized asphalt, which is typically much quieter than nonrubberized open-graded asphalts. The measured and predicted sounds levels at the reference microphone for three nearly neutral periods at the No-Barrier site and three nearly neutral periods at the Barrier site were compared to develop an adjustment factor. Read the entire page →
From page 281... ... Appendix D: Modeling D-7 Mic Location LAeq (dBA) Predicted (Adjusted) Read the entire page →
From page 282... ... D-8 How Weather Affects the Noise You Hear from Highways TNM Pavement Adjustment = 4.2 dB Figure D-3. Sound level results for No-Barrier site, neutral conditions, 2/26/16 at 9:45. Read the entire page →
From page 283... ... Appendix D: Modeling D-9 Mic Location LAeq (dBA) Measured Predicted (Adjusted) Read the entire page →
From page 284... ... D-10 How Weather Affects the Noise You Hear from Highways TNM Pavement Adjustment = 3.6 dB Figure D-6. Sound level results for Barrier site, neutral conditions, 3/7/16 at 1:30. Read the entire page →
From page 285... ... D-11 In this chapter, we present calculations of traffic noise levels with the Harmonoise model and the PE model. From the calculated levels, we derive values of a quantity that we call the meteorological effect on the traffic noise level. Read the entire page →
From page 286... ... D-12 How Weather Affects the Noise You Hear from Highways contribution to the effective sound speed increases with height when the temperature increases with height. Figure D-8 illustrates how the vertical profiles of the temperature and the vector wind determine the profile of the effective sound speed. Read the entire page →
From page 287... ... Appendix D: Modeling D-13 Figure D-8. Illustration how the vertical profiles of the temperature and the vector wind determine the profile of the effective sound speed. Read the entire page →
From page 288... ... D-14 How Weather Affects the Noise You Hear from Highways vector wind class normal vector wind (height 10 m) Wind speed u10 (height 10 m) Read the entire page →
From page 289... ... Appendix D: Modeling D-15 represented by a point source (see Figure D-11) Read the entire page →
From page 290... ... D-16 How Weather Affects the Noise You Hear from Highways by a point source, to which the Harmonoise point-to-point model can be applied. The overall sound level at a receiver is the sum of the contributions from all the point sources. Read the entire page →
From page 291... ... Appendix D: Modeling D-17 Model Parameters Figure D-14 shows the geometry used for the calculations with Harmonoise. The geometry is an approximation of the measurement geometry, with a straight road and rounded distances. Read the entire page →
From page 292... ... D-18 How Weather Affects the Noise You Hear from Highways propagation distance because with increasing propagation distance sound waves travel through a higher layer of the atmosphere. Atmospheric turbulence is represented in the Harmonoise model by a scattering term, with a single numerical input parameter γ (see the article in Acta Acustica (Salomons et al. Read the entire page →
From page 293... ... Appendix D: Modeling D-19 • In a downward refracting atmosphere, the effective sound speed difference is positive, • In a non-refracting atmosphere, the effective sound speed difference is zero, and • In an upward refracting atmosphere, the effective sound speed difference is negative. The quantity on the vertical axis in Figure D-16 is the meteorological effect, i.e., the sound level difference between the actual refracting atmosphere and the corresponding non-refracting (neutral) Read the entire page →
From page 294... ... D-20 How Weather Affects the Noise You Hear from Highways Figure D-16. Graph of the values of the meteorological effect from Table D-6 as a function of the effective sound speed difference between height 10 m and height zero Figure D-17. Read the entire page →
From page 295... ... Appendix D: Modeling D-21 difference between upward refraction and downward refraction is about 15 dB according to the measurements at 240 m, while the Harmonoise results in Figure D-16 show that the difference is about 25 dB. It is not clear why the calculations show a larger meteorological effect than the measurements do. Read the entire page →
From page 296... ... D-22 How Weather Affects the Noise You Hear from Highways vector wind class stability class distance from road (m) 15 30 60 120 240 480 960 V1 strong downwind S1 1 1 3 5 8 11 15 S2 1 1 3 5 8 12 13 S3 1 1 3 6 9 9 15 S4 1 1 3 6 7 7 10 S5 1 2 3 6 5 3 13 V2 weak downwind S1 0 -1 -4 -15 -21 -16 -9 S2 0 0 -2 -3 -1 2 3 S3 0 0 0 2 5 9 13 S4 1 1 2 5 8 8 13 S5 1 1 3 6 5 4 13 V3 zero (zero wind) Read the entire page →
From page 297... ... Appendix D: Modeling D-23 Figure D-18. As Figure D-16, for ground flow resistivity r = 100 kPa s m–2 instead of r = 200 kPa s m–2. Read the entire page →
From page 298... ... D-24 How Weather Affects the Noise You Hear from Highways Figure D-19. As Figure D-16, for ground flow resistivity r = 500 kPa s m–2 instead of s = 200 kPa s m–2. Read the entire page →
From page 299... ... vector wind class stability class distance from road (m) 15 30 60 120 240 480 960 V1 strong downwind S1 1 1 2 5 7 10 13 S2 1 1 2 5 7 11 11 S3 1 1 3 5 8 8 13 S4 1 1 3 5 6 7 9 S5 1 1 3 5 5 3 11 V2 weak downwind S1 0 -1 -4 -14 -16 -12 -5 S2 0 0 -2 -3 -2 1 2 S3 0 0 0 1 4 8 11 S4 1 1 2 4 8 7 12 S5 1 1 3 5 5 4 12 V3 zero (zero wind) Read the entire page →
From page 300... ... stability class distance from road (m) 15 30 60 120 240 480 960 V1 strong downwind S1 1 1 2 5 7 10 13 S2 1 1 3 5 7 11 12 S3 1 1 3 5 8 8 14 S4 1 1 3 5 6 7 10 S5 1 1 3 5 5 3 12 V2 weak downwind S1 0 -1 -4 -15 -19 -16 -9 S2 0 0 -2 -3 -2 1 2 S3 0 0 0 1 5 8 12 S4 1 1 2 5 8 7 12 S5 1 1 3 5 5 3 13 V3 zero (zero wind) Read the entire page →
From page 301... ... Appendix D: Modeling D-27 Figure D-22. Geometry used for the Harmonoise calculations for the barrier site. Read the entire page →
From page 302... ... D-28 How Weather Affects the Noise You Hear from Highways The calculation is performed for single frequencies, so a series of calculations is performed to obtain the complete sound spectrum of a broadband point source. The vertical grid spacing is about one-tenth of a wavelength. Read the entire page →
From page 303... ... Appendix D: Modeling D-29 Figure D-23. Schematic representation of the finitedifference grid used for the PE model. Read the entire page →
From page 304... ... D-30 How Weather Affects the Noise You Hear from Highways For Figures D-24 and D-25, spectral results were converted to broadband levels by using an emission sound power spectrum calculated with Harmonoise for a single passenger car at 100 km/h. The shape of the spectrum is similar to the shape of the emission spectrum shown in Figure D-15. Read the entire page →
From page 305... ... Appendix D: Modeling D-31 In summary, we conclude that the Harmonoise model gives results that are in reasonable agreement with PE results. Here we focus on the results for a turbulent atmosphere, since atmospheres in practice are always turbulent. Read the entire page →
From page 306... ... D-32 The team modeled the No-Barrier and Barrier sites using the FHWA Traffic Noise Model (TNM 2.5) computer program and compared the measured sound levels to the TNM-predicted sound levels for neutral conditions. Read the entire page →
From page 307... ... Appendix D: Modeling D-33 in the measurements, so the S-shaped curve may have reached higher values if these conditions would have been included. Another part of the explanation may be that the turbulence strength was higher during the measurements than assumed for the calculations, as represented by the turbulence parameter γ = 10 × 10–6; this was confirmed by a separate calculation for γ = 30 × 10–6. Read the entire page →
From page 308... ... D-34 The 30 meteorological classes defined in Chapter D-3 are combinations of 6 vector wind classes and 5 stability classes. For each vector wind class, values of wind speed u10 (at 10 m height) Read the entire page →
From page 309... ... Appendix D: Modeling D-35 ( ) Read the entire page →
From page 310... ... D-36 How Weather Affects the Noise You Hear from Highways Figure Annex 1. Point source effective sound speed profiles, for a = 0. Read the entire page →
From page 311... ... Appendix D: Modeling D-37 Figure Annex 2. Point source effective sound speed profiles, for a = 60 deg. Read the entire page →
From page 312... ... D-38 In this annex the linearization of loglin sound speed profiles is described, following the approach developed in the European project Imagine (IMA4DR-070323-EEC-10, p. Read the entire page →
From page 313... ... Appendix D: Modeling D-39 Quantities q, hM, d, k, and γ are defined through the following relations. Read the entire page →
From page 314... ... D-40 How Weather Affects the Noise You Hear from Highways or 2 1 (14c) Read the entire page →

From page 275...

... D-1 Erik Salomons, TNO Darlene Reiter and Rennie Williamson, Bowlby & Associates Roger Wayson, Wyle Ken Kaliski and Ryan Haac, RSG Aaron Hastings, Volpe A P P E N D I X D Modeling