Previous studies indicate that residents may benefit from a “quiet side” to their dwellings. The influence of the level of road traffic noise exposure at the least exposed side on road traffic noise annoyance was studied in Amsterdam, The Netherlands. Road traffic noise exposure was assessed at the most and least exposed façade (Lden,most and Lden,least respectively) of dwellings for subjects in a population based survey (N = 1,967). It was investigated if and to what extent relative quietness at the least exposed façade affected the level of road traffic noise annoyance by comparing two groups: (1) The subgroup with a relatively quiet façade; (2) the subgroup without a relatively quiet façade (large versus small difference in exposure between most and least exposed façade; DIF ≥ 10 dB and DIF < 10 dB respectively). In addition, it was investigated if and to what extent Lden,least affected the level of road traffic noise annoyance. Results indicate a significantly lower road traffic noise annoyance score at a given Lden,most, in the subgroup with DIF ≥ 10 dB versus DIF < 10 dB. Furthermore, results suggest an effect of Lden,least independent of Lden,most. The estimated size of the effect expressed in an equivalent change in Lden,most approximated 5 dB for both the difference between the two subgroups (DIF ≥ 10 dB and DIF < 10 dB), and for a 10 dB change in Lden,least.
Propagation of sound waves in air can be considered as a special case of fluid dynamics. Consequently, the lattice Boltzmann method (LBM) for fluid flow can be used for simulating sound propagation. In this article application of the LBM to sound propagation is illustrated for various cases: free-field propagation, propagation over porous and non-porous ground, propagation over a noise barrier, and propagation in an atmosphere with wind. LBM results are compared with solutions of the equations of acoustics. It is found that the LBM works well for sound waves, but dissipation of sound waves with the LBM is generally much larger than real dissipation of sound waves in air. To circumvent this problem it is proposed here to use the LBM for assessing the excess sound level, i.e. the difference between the sound level and the free-field sound level. The effect of dissipation on the excess sound level is much smaller than the effect on the sound level, so the LBM can be used to estimate the excess sound level for a non-dissipative atmosphere, which is a useful quantity in atmospheric acoustics. To reduce dissipation in an LBM simulation two approaches are considered: i) reduction of the kinematic viscosity and ii) reduction of the lattice spacing.
Road traffic noise in urban areas is a major source of annoyance. A quiet façade has been hypothesized to beneficially affect annoyance. However, only a limited number of studies investigated this hypothesis, and further quantification is needed. This study investigates the effect of a relatively quiet façade on the annoyance response. Logistic regression was performed in a large population based study (GLOBE, N~18,000), to study the association between road traffic noise exposure at the most exposed dwelling façade (L(den)) and annoyance in: (1) The subgroup with a relatively quiet façade (large difference in road traffic noise level between most and least exposed façade (Q>10 dB); (2) the subgroup without a relatively quiet façade (Q<10 dB). Questionnaire data were linked to individual exposure assessment based on detailed spatial data (GIS) and standard modeling techniques. Annoyance was less likely (OR(Q) (>10)
A computational study of road traffic noise in cities is presented. Based on numerical boundary-element calculations of canyon-to-canyon propagation, an efficient engineering algorithm is developed to calculate the effect of multiple reflections in street canyons. The algorithm is supported by a room-acoustical analysis of the reverberant sound fields in the source and receiver canyons. Using the algorithm, a simple model for traffic noise in cities is developed. Noise maps and exposure distributions of the city of Amsterdam are calculated with the model, and for comparison also with an engineering model that is currently used for traffic noise impact assessments in cities. Considerable differences between the two model predictions are found for shielded buildings with day-evening-night levels of 40-60 dB at the facades. Further, an analysis is presented of level differences between the most and the least exposed facades of buildings. Large level differences are found for buildings directly exposed to traffic noise from nearby roads. It is shown that by a redistribution of traffic flow around these buildings, one can achieve low sound levels at quiet sides and a corresponding reduction in the percentage of highly annoyed inhabitants from typically 23% to 18%.
An optimized method is presented for the numerical evaluation of the sound field generated by an incoherent line source, which is commonly used to model road and rail traffic noise. Two different solutions for the numerical integration over the line source are distinguished, a point source solution and a line source solution. With proper segmentation of the line source, both solutions yield accurate results. Special attention is paid to receiver positions close to the (infinite) line through the (finite) line source. At these positions, conventional methods give numerical errors, which occur frequently in calculations of large-scale noise maps of cities, employing automatically generated geographical input data. The problems are avoided by using the optimized method presented here. The method is based on a combination of angular segmentation and linear segmentation of the line source and can be used to minimize the number of point-to-point calculations for noise mapping.
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