Investigation of traffic noise attenuation potential of an urban highway underpass.

JOAO Pessoa (Paraiba, Brazil); BRAZIL

• An underpass copes with noise attenuation without introducing aesthetical problems. • Measurement and simulations in a neighborhood of a highway underpass were conducted. • The existing L-shape edge was effective only at the border of the underpass. • Depth and shape of underpass edge are associated to varied noise attenuations. Road traffic is the main contributor to noise in urban areas. A case of concern is urban highways, due to the intensity of the emitted noise. Acoustic barriers are one of the solutions usually adopted to reduce highway traffic noise in this case. However, they have a negative visual impact on the urban landscape. An underpass could be a solution that provides noise attenuation without introducing aesthetical problems to the urban area. This work investigates the noise attenuation of a highway underpass aiming to confirm its efficiency as a solution for the minimization of traffic noise and explores a variety of scenarios that could influence the noise propagation. Noise measurements and the collection of input data used in noise simulations were conducted at an urban highway located in the city of João Pessoa in Brazil. The investigation was focused on the highway underpass with an L-shaped top edge, which is acting as a parallel acoustic barrier to an adjacent residential area. In addition, simulations were performed using the software SoundPLAN. Five scenarios were simulated: the actual situation and four scenarios with different depths of the underpass and changes on its edge. It was found that the existing L-shape edge of the underpass is positively influential only at points at the immediate vicinity of the border and resulted in an additional average attenuation of 1.3 dB in this region. However, in general, the average attenuation due to the underpass for the points in the whole acoustic shadow zone was 10.6 dB with the actual L-shape edge, and 13.1 dB from simulations when the L-shaped edge was removed. From simulations involving changing the depth of the underpass, it was observed that there was no linear relationship between attenuation versus depth. The simulation results showed that adding an L-shape edge with its current length is not efficient regardless of the depth of the underpass. The results thus confirmed the underpass as an effective solution for the mitigation of highway traffic noise and provided additional insight on the role of the depth associated to changes on the geometry of the top of the underpass. [ABSTRACT FROM AUTHOR]

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