Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range
<p>A-weighted sound power level (Lw) spectrum. Road traffic noise spectrum according to [<a href="#B38-applsci-10-05746" class="html-bibr">38</a>].</p> "> Figure 2
<p>A-weighted sound power level (Lw) spectrum of a typical siren by Howard [<a href="#B40-applsci-10-05746" class="html-bibr">40</a>].</p> "> Figure 3
<p>Car configurations (‘1′, person, and ‘2′, balcony).</p> "> Figure 4
<p>Siren vehicle configurations (‘3′, person and ‘4′, balcony).</p> "> Figure 5
<p>Barrier caps considered: (<b>1</b>) Y-shaped; (<b>2</b>) rectangular; (<b>3</b>) T-shaped; (<b>4</b>) cylinder with radius w/2; and (<b>5</b>) trapezoid-shaped.</p> "> Figure 6
<p>Examples of double-cap barriers of all possible existing combinations. The total envelope size is maintained.</p> "> Figure 7
<p>‘Calculate’ subroutine flow diagram.</p> "> Figure 8
<p>PARDOS (Pérdidas Acústicas por Reflexión y Difracción de la Onda Sonora) main GUI (graphical user interface) with ‘About’ pop-up window.</p> "> Figure 9
<p>Notation used in a single diffracting wedge. Reflection coefficients for the 0 face, with incidence angle <span class="html-italic">θ</span><sub>1</sub>, and for the <span class="html-italic">n</span> face, with reflection angle <span class="html-italic">v</span>π−<span class="html-italic">θ</span><sub>2</sub>.</p> "> Figure 10
<p>A-weighted sound power level (<span class="html-italic">Lw</span>), SPL (<span class="html-italic">Lp</span> dBA 1/3rd octave) equivalent spectra of road traffic noise at 1/3rd octave frequency band and 1 Hz resolution band (<span class="html-italic">Lp</span> dBA 1 Hz).</p> "> Figure 11
<p>A-weighted sound power level (Lw), SPL (<span class="html-italic">Lp</span> dBA 1/3rd octave) equivalent spectra of a typical siren [<a href="#B40-applsci-10-05746" class="html-bibr">40</a>] at 1/3rd octave frequency band and 1 Hz resolution band (<span class="html-italic">Lp</span> dBA 1 Hz).</p> "> Figure 12
<p><span class="html-italic">IL</span> in Configuration 1 ‘Car–Person’ for single caps and a single screen barrier as a reference.</p> "> Figure 13
<p><span class="html-italic">IL</span> in Configuration 2 ‘Car–Balcony’ for single caps and a single screen barrier as a reference.</p> "> Figure 14
<p><span class="html-italic">IL</span> in Configuration 3 ‘Ambulance–Person’ for single caps and a single screen barrier as a reference.</p> "> Figure 15
<p><span class="html-italic">IL</span> in Configuration 4 ‘Ambulance–Balcony’ for single caps and a single screen barrier as a reference.</p> "> Figure 16
<p><span class="html-italic">IL</span> for Configuration 1 (‘Car–Person’) considering double caps formed with Y-shaped structures and a single screen barrier as a reference.</p> "> Figure 17
<p><span class="html-italic">IL</span> in Configuration 2 (‘Car–Balcony’) using double caps formed with Y-shaped structures and a single screen barrier as a reference.</p> "> Figure 18
<p><span class="html-italic">IL</span> in Configuration 3 (‘Ambulance–Person’) using double caps formed with Y-shaped structures and a single screen barrier as a reference.</p> "> Figure 19
<p><span class="html-italic">IL</span> in Configuration 4 (‘Ambulance–Balcony’) using double caps formed with Y-shaped structures and a single screen barrier as a reference.</p> "> Figure 20
<p><span class="html-italic">IL</span> (solid lines) with double-Y caps in the four configurations (CP, Car–Person; CB, Car–Balcony; AP, Ambulance–Person; AB, Ambulance–Balcony) and attenuation losses (dashed lines) in free space (‘Att (fs)’, without barrier) in the corresponding receiver locations.</p> "> Figure 21
<p>Attenuation map at 1500 Hz in the ‘car’ location. Barrier with the ‘Y–Y’ cap and 3 m height.</p> "> Figure 22
<p><span class="html-italic">IL</span> map at 1500 Hz in the ‘car’ location. Barrier with the ‘Y–Y’ cap and 3 m height.</p> "> Figure 23
<p>Attenuation map at 1500 Hz at the ‘ambulance’ location. Barrier with the ‘Y–Y’ cap and 3 m height.</p> "> Figure 24
<p><span class="html-italic">IL</span> map at 1500 Hz at the ‘ambulance’ location. Barrier with ‘the Y–Y’ cap and 3 m height.</p> "> Figure 25
<p>A-weighted SPL spectrum with 1 Hz resolution in Configuration 1 (Car–Person) for ‘YY’ cap with and without ground reflection. The screen barrier SPL spectrum is shown as a reference.</p> "> Figure 26
<p>A-weighted sound pressure level (SPL) spectrum in 1 Hz bands in Configuration 2 (Car–Balcony) for the ‘YY’ cap with and without ground reflection. The screen barrier SPL spectrum is shown as a reference.</p> "> Figure 27
<p>A-weighted SPL spectrum in 1 Hz bands in Configuration 3 (Ambulance–Person) for the ‘YY’ cap with and without ground reflection. The screen barrier SPL spectrum is shown as a reference.</p> "> Figure 28
<p>A-weighted SPL spectrum in 1 Hz bands in Configuration 4 (Ambulance–Balcony) for ‘YY’ cap with and without ground reflection. The screen barrier SPL spectrum is shown as a reference.</p> "> Figure 29
<p>All configurations with a road slope at angle α.</p> "> Figure 30
<p>Influence of sloping and reflecting grounds on the SPL spectrum for the ‘Car–Person’ configuration and barrier with optimum double Y caps.</p> "> Figure 31
<p>Triple Y-cap.</p> ">
Abstract
:1. Introduction
2. Materials and Methods
2.1. Traffic Noise Spectrum
2.2. Propagation Environment
- Noise sources (Tx1 and Tx2, respectively) that radiate sound spherically at a height (htx1) of 0.5 m (location C for “car”) with the SPL spectrum displayed in Figure 1, or from a vehicle with a light-bar mounted siren at a height (htx2) of 2.5 m (location A for “ambulance”) with the SPL spectrum displayed in Figure 2.
- Barrier located at a distance (d1) of 3 m from the sound source and a height (hbar) of 3 m with a maximum width (w) of 0.4 m (including their single or double cap on the top).
- Potential sound receivers (Rx1 and Rx2) positioned at a distance (d2) of 7 m from the barrier at heights of hRx1 = 1.7 m (location P for “person”) and hRx2 = 5 m (location B for “balcony”), respectively.
- Configuration 1 (C–P), ‘Car–Person’.
- Configuration 2 (C–B), ‘Car–Balcony’.
- Configuration 3 (A–P), ‘Ambulance–Person’.
- Configuration 4 (A–B), ‘Ambulance–Balcony’.
2.3. Theoretical Method
- represents the SPL from the source;
- , with representing the slant distances for the links of paths chosen, between each node’s geometrical centers;
- represents the wavenumber;
- N represents the quantity of nodes for every path;
- represents the diffraction coefficient and the reflection coefficient; application is dependent on the form of incidence either obstacle or ground;
- α is the air-absorbent coefficient in Np/m, according to [48]. In turn, this parameter depends on the following input variables, which are related to the source’s frequency emission (f) and the physical properties of the air: static pressure (Ps), Celsius temperature (T), and percentage relative humidity (H).
2.3.1. Pressure Diffraction Coefficients (Dn)
2.3.2. Pressure Reflection Coefficients (Rn, Ro)
2.3.3. Global Sound Pressure Level Estimation
- Transformation of the A-weighted power level Lw (dBA) into the A-weighted SPL Lp (dBA) at 1 m:
- Normalization of the pressure level from one-third octave band spectra to 1 Hz frequency resolution with a linear distribution. A simple loop runs for all the center frequencies of each 1/3rd octave frequency band (. The sound pressure levels at the 1 Hz band resolution was obtained by normalizing each value by their correspondent frequency band , as shown in Equations (27) to (30):
- Obtaining the pressure attenuation A(f) in dB as a function of frequency using the PARDOS software tool with the barrier cap configuration presenting the highest IL. Then, an interpolation of the different frequencies of the source is carried out.
- Subtraction of the obtained attenuation (A):
- Calculation of the global final SPL for the whole frequency range (n frequency bins):
3. Results and Discussion
3.1. Influence of Sloping Ground on Global Acoustic Insertion Losses
3.2. Influence of Increasing the Number of Diffracting Devices (More than Two) while Maintaining the Same Envelope Size
4. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
- Berglund, B.; Lindvall, T.; Schwela, D.H. (Eds.) Guidelines for Community Noise; World Health Organization: Geneva, Switzerland, 1999; Available online: http://whqlibdoc.who.int/hq/1999/a68672.pdf (accessed on 22 July 2010).
- JRC European Commission. Burden of Disease from Environmental Noise. Quantification of Healthy Life Years Lost in Europe; World Health Organization: Copenhagen, Denmark, 2011; ISBN 978 92 890 0229 5. [Google Scholar]
- Fredianelli, L.; Carpita, S.; Licitra, G. A procedure for deriving wind turbine noise limits by taking into account annoyance. Sci. Total. Environ. 2019, 648, 728–736. [Google Scholar] [CrossRef] [PubMed]
- Basner, M.; Babisch, W.; Davis, A.; Brink, M.; Clark, C.; Janssen, S.; Stansfeld, S. Auditory and non-auditory effects of noise on health. Lancet 2014, 383, 1325–1332. [Google Scholar] [CrossRef] [Green Version]
- Sygna, K.; Aasvang, G.M.; Aamodt, G.; Oftedal, B.; Krog, N.H. Road traffic noise, sleep and mental health. Environ. Res. 2014, 131, 17–24. [Google Scholar] [CrossRef]
- Licitra, G.; Fredianelli, L.; Petri, D.; Vigotti, M.A. Annoyance evaluation due to overall railway noise and vibration in Pisa urban areas. Sci. Total. Environ. 2016, 568, 1315–1325. [Google Scholar] [CrossRef]
- Lercher, P.; Evans, G.W.; Meis, M. Ambient noise and cognitive processes among primary schoolchildren. Environ. Behav. 2003, 35, 725–735. [Google Scholar] [CrossRef]
- Chetoni, M.; Fredianelli, L.; Minichilli, F.; Cori, L.; Licitra, G.; Bianco, F. Correlation between perceived and measured noise, within the Gioconda project. In Proceedings of the ICSV 2016–23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics, Athens, Greece, 10–14 July 2016. [Google Scholar]
- Vienneau, D.; Schindler, C.; Perez, L.; Probst-Hensch, N.; Röösli, M. Hypertension ischemic heart disease. The relationship between transportation noise exposure and ischemic heart disease: A meta-analysis. Environ. Res. 2015, 138, 372–380. [Google Scholar] [CrossRef]
- Roswall, N.; Raaschou-Nielsen, O.; Ketzel, M.; Gammelmark, A.; Overvad, K.; Olsen, A.; Sørensen, M. Long-term residential road traffic noise and NO2 exposure in relation to risk of incident myocardial infarction–A Danish cohort study. Environ. Res. 2017, 156, 80–86. [Google Scholar] [CrossRef]
- Roswall, N.; Raaschou-Nielsen, O.; Jensen, S.S.; Tjønneland, A.; Sørensen, M. Long-term exposure to residential railway and road traffic noise and risk for diabetes in a Danish cohort. Environ. Res. 2018, 160, 292–297. [Google Scholar] [CrossRef]
- Śliwińska-Kowalska, M.; Zaborowski, K. WHO Environmental Noise Guidelines for the European Region: A Systematic Review on Environmental Noise and Permanent Hearing Loss and Tinnitus. Int. J. Environ. Res. Public Health 2017, 14, 1139. [Google Scholar] [CrossRef]
- Del Pizzo, A.; Luca, T.; Moro, A.; Bianco, F.; Fredianelli, L. Influence of texture on tyre road noise spectra in rubberized pavements. Appl. Acoust. 2020, 159, 107080. [Google Scholar] [CrossRef]
- Teti, L.; De León, G.; Del Pizzo, A.; Moro, A.; Bianco, F.; Fredianelli, L.; Licitra, G. Modelling the acoustic performance of newly laid low-noise pavements. Constr. Build. Mater. 2020, 247, 118509. [Google Scholar] [CrossRef]
- Praticò, F.G.; Moro, A. Permeability and volumetrics of porous asphalt concrete: A theoretical and experimental investigation. Road Mater. Pavement Des. 2007, 8, 799–817. [Google Scholar] [CrossRef]
- Praticò, F.G. Roads and loudness: A more comprehensive approach. Road Mater. Pavement Des. 2001, 2, 359–377. [Google Scholar] [CrossRef]
- Licitra, G.; Cerchiai, M.; Teti, L.; Ascari, E.; Bianco, F.; Cheton, M. Performance assessment of low-noise road surfaces in the Leopoldo project: Comparison and validation of different measurement methods. Coatings 2015, 5, 3–25. [Google Scholar] [CrossRef]
- Fredianelli, L.; Del Pizzo, A.; Licitra, G. Recent developments in sonic crystals as barriers for road traffic noise mitigation. Environments 2019, 6, 14. [Google Scholar] [CrossRef] [Green Version]
- Radosz, J. Acoustic performance of noise barrier based on sonic crystals with resonant elements. Appl. Acoust. 2019, 155, 492–499. [Google Scholar] [CrossRef]
- Godinho, L.; Redondo, J.; Amado-Mendes, P. The method of fundamental solutions for the analysis of infinite 3D sonic crystals. Eng. Anal. Bound. Elem. 2019, 98, 172–183. [Google Scholar] [CrossRef]
- Watts, G.R. Acoustic performance of new designs of traffic noise barriers: Full-scale tests. J. Sound Vib. 1994, 177, 289–305. [Google Scholar] [CrossRef]
- Watts, G.R. Acoustic performance of a multiple-edge noise barrier profile at motorway sites. Appl. Acoust. 1996, 47, 47–66. [Google Scholar] [CrossRef]
- Watts, G.R.; Morgan, P.A. Acoustic performance of an interference type noise barrier. Appl. Acoust. 1964, 49, 1–16. [Google Scholar] [CrossRef]
- Watts, G.R. Effectiveness of novel shaped bunds in reducing traffic noise. Proc. Inst. Acoust. 1999, 21, 41–50. [Google Scholar]
- Haan, C.; Kim, S. Comparison of the insertion loss of noise barriers with different shapes of upper structure. In Proceedings of the Road Traffic Noise Modeling and Noise Barrier, 22nd International Congress on Acoustics, ICA, Buenos Aires, Argentina, 5–9 September 2016. [Google Scholar]
- Ishizuka, T.; Fujiwara, K. Performance of noise barriers with various edge shapes and acoustical conditions. Appl. Acoust. 2004, 65, 125–141. [Google Scholar] [CrossRef]
- Asdrubali, F. On the experimental evaluation of the performances of noise barrier diffracting devices. Acta Acust. United Acust. 2007, 93, 659–669. [Google Scholar]
- Monazzam, M.; Fard, S. Performance of passive and reactive profiled median barriers in traffic noise reduction. J. Zhejiang Univ. Sci. A Appl. Phys. Eng. 2011, 12, 78–86. [Google Scholar] [CrossRef]
- Yamamoto, K. Japanese experience to reduce road traffic noise by barriers with noise-reducing devices. In Proceedings of the 10th European Congress and Exposition on Noise Control Engineering, EuroNoise, Maastricht, The Netherlands, 31 May–3 June 2015; Volume 31. [Google Scholar]
- Monazzam, M.; Abbasi, M.; Yazdanirad, S. Performance Evaluation of T-Shaped Noise Barriers Covered with Oblique Diffusers Using Boundary Element Method. Arch. Acoust. 2019, 44, 521–531. [Google Scholar] [CrossRef]
- Morgan, P. QUESTIM. Assessing the Acoustic Durability of Noise Barriers on NRA Road Networks; CEDR Transnational Road Research Programme; CEDR: London, UK, 2014. [Google Scholar]
- Vanhooreweder, B.; Marcocci, S.; De Leo, A. State of the Art in Managing Road Traffic Noise: Noise Barriers; Technical Report 2017-02; CEDR: London, UK, 2016; ISBN 979-10-93321-27-1. [Google Scholar]
- May, D.N.; Osman, M.M. The performance of sound absorptive, reflective and T-profile noise barriers in Toronto. J. Sound Vib. 1980, 71, 65–71. [Google Scholar] [CrossRef]
- Can, A.; Leclercq, L.; Lelong, J.; Botteldooren, D. Traffic Noise Spectrum Analysis: Dynamic Modeling vs. Experimental Observations. Appl. Acoust. 2010, 71, 765–770. [Google Scholar] [CrossRef] [Green Version]
- Jakovljevic, B.; Paunovic, K.; Belojevic, G. Road-Traffic Noise and Factors Influencing Noise Annoyance in an Urban Population. Environ. Int. 2009, 35, 552–556. [Google Scholar] [CrossRef]
- Dravitzki, V.; Walton, D.K.; Wood, W.B. Determining the Influence of New Zealand Road Surfaces on Noise Levels and Community Annoyance; Report 292; Land Transport New Zealand: Wellington, New Zealand, 2006. [Google Scholar]
- EN 1793-3. Road Traffic Noise Reducing Devices–Test Method for Determining the Acoustic Performance–Part 3; Normalized Traffic Noise Spectrum; European Committee for Standardization: Brussels, Belgium, 1997. [Google Scholar]
- Baulac, M.; Guillou, A.; Defrance, J.; Jean, P. Calculations of low height noise barriers efficiency by using Boundary Element Method and optimization algorithms. J. Acoust. Soc. Am. 2008. [Google Scholar] [CrossRef]
- Catchpole, K.R. A framework for the design of ambulance sirens. Ergonomics 2007, 50, 1287–1301. [Google Scholar] [CrossRef]
- Howard, C. Acoustic characteristics for effective ambulance sirens. Aust. Acoust. Soc. 2011, 39, 43–53. [Google Scholar]
- U.S. Department of Transportation Federal Highway Administration. Available online: https://www.fhwa.dot.gov/Environment/noise/noise_barriers/inventory/summary/stable713.cfm (accessed on 18 August 2020).
- Morgan, P. Review of Japanese Noise Barrier Research (DWW-2004-081); Rijkswaterstatt Dienst Verkeer en Scheepvaart: Delft, The Netherlands, 2004. [Google Scholar]
- Pardo-Quiles, D.; Rodríguez, J.-V. A Fast UTD-based Method for the Analysis of Multiple Acoustic Diffractions over a Series of Obstacles with Arbitrary Modeling, Height and Spacing. Symmetry 2020, 12, 1–24. [Google Scholar]
- Keller, B. Geometrical theory of diffraction. J. Opt. Soc. Am. 1962, 52, 116–130. [Google Scholar] [CrossRef] [PubMed]
- Kouyoumjian, R.G.; Pathak, P.H. A uniform geometrical theory of di_raction for an edge in a perfectly conducting surface. Proc. IEEE 1974, 62, 1448–1461. [Google Scholar] [CrossRef] [Green Version]
- Pierce, A.D. Diffraction of sound around corners and over wide barriers. J. Acoust. Soc. Am. 1974, 55, 941–955. [Google Scholar] [CrossRef]
- Min, H.; Qiu, X. Multiple acoustic diffraction around rigid parallel wide barriers. J. Acoust. Soc. Am. 2009, 126, 179–186. [Google Scholar] [CrossRef]
- Rasmussen, K. Calculation Methods for the Physical Properties of Air Used in the Calibration of Microphones; Report PL-11b; Department of Acoustic Technology, Technical University of Denmark: Lyngby, Denmark, 1997. [Google Scholar]
- McNamara, D.A.; Pistorius, C.W.I.; Malherbe, J.A.G. Introduction to the Uniform Geometrical Theory of Diffraction; Artech House: Norwood, MA, USA, 1990. [Google Scholar]
- Koutitas, G.; Tzaras, C. A UTD solution for multiple rounded surfaces. IEEE Trans. Antennas Propag. 2006, 54, 4. [Google Scholar] [CrossRef]
- Rodríguez, J.-V.; Molina-Garcia-Pardo, J.-M.; Juan-Llácer, L. A hybrid UTD-PO solution for multiple-cylinder diffraction analysis assuming spherical-wave incidence. IEEE Trans. Antennas Propag. 2008, 56, 3078–3081. [Google Scholar] [CrossRef]
- Kinsler, L.E.; Frey, A.R.; Coppens, A.B.; Sanders, J.V. Fundamentals of Acoustics; Wiley: Hoboken, NJ, USA, 1999; ISBN 0-471-84789-5. [Google Scholar]
- Fahy, F.; Rossing, T.D. Foundations of Engineering Acoustics; Elsevier Academic Press: London, UK, 2001; ISBN 0-12-247665-4. [Google Scholar]
Scenario | ‘Car’ (Road Traffic) Lw (dBA) = 110.2 Lp(dBA) = 99.2 | ‘Ambulance’ (Ambulance Siren) Lw (dBA) = 122.6 Lp(dBA) = 111.6 | ||
---|---|---|---|---|
LdBArx ‘Person’ Conf 1 | LdBArx ‘Balcony’ Conf 2 | LdBArx ‘Person’ Conf 3 | LdBArx ‘Balcony’ Conf 4 | |
Free path, without barrier | 87.8 | 85.1 | 99.5 | 97.9 |
Plain screen barrier without caps | 63.7 | 66.7 | 78.6 | 89.2 |
Y-shaped double cap on top of barrier | 50.0 | 60.4 | 64.6 | 88.2 |
Y-shaped double cap on top of barrier w/o ground reflection | 47.7 | 58.9 | 63.6 | 88.2 |
Scenario | ‘Car’ (Road Traffic) Lw (dBA) = 110.2 Lp(dBA) = 99.2 | ‘Ambulance’ (Ambulance Siren) Lw (dBA) = 122.6 Lp(dBA) = 111.6 | ||
---|---|---|---|---|
LdBArx ‘Person’ Conf 1 | LdBArx ‘Balcony’ Conf 2 | LdBArx ‘Person’ Conf 3 | LdBArx ‘Balcony’ Conf 4 | |
Y-shaped double cap with ground slope angle of 5° | 45.7 | 61.1 | 59.8 | 87.8 |
Y-shaped double cap with ground slope angle of 5° and w/o ground reflection | 42.7 | 59.7 | 58.1 | 87.8 |
Y-shaped double cap with ground slope angle of 10° | 46.3 | 61.4 | 60.7 | 87.4 |
Y-shaped double cap with ground slope angle of 10° and w/o ground reflection | 43.1 | 59.9 | 58.8 | 87.4 |
Scenario | ‘Car’ (Road Traffic) Lw (dBA) = 110.2 Lp(dBA) = 99.2 | ‘Ambulance’ (Ambulance Siren) Lw (dBA) = 122.6 Lp(dBA) = 111.6 | ||
---|---|---|---|---|
LdBArx ‘Person’ Conf 1 | LdBArx ‘Balcony’ Conf 2 | LdBArx ‘Person’ Conf 3 | LdBArx ‘Balcony’ Conf 4 | |
Y-shaped triple cap on top of barrier with ground reflection | 53.4 | 52.9 | 67.2 | 87.8 |
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Pardo-Quiles, D.; Rodríguez, J.-V.; Molina-García-Pardo, J.-M.; Juan-Llácer, L. Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range. Appl. Sci. 2020, 10, 5746. https://doi.org/10.3390/app10175746
Pardo-Quiles D, Rodríguez J-V, Molina-García-Pardo J-M, Juan-Llácer L. Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range. Applied Sciences. 2020; 10(17):5746. https://doi.org/10.3390/app10175746
Chicago/Turabian StylePardo-Quiles, Domingo, José-Víctor Rodríguez, Jose-Maria Molina-García-Pardo, and Leandro Juan-Llácer. 2020. "Traffic Noise Mitigation Using Single and Double Barrier Caps of Different Shapes for an Extended Frequency Range" Applied Sciences 10, no. 17: 5746. https://doi.org/10.3390/app10175746