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Page • 550 Principles and Standards Bridge definition local in the road file definition of the distances from the middle to the left and from the middle to the right with heights above the road Noise shielded by the side of the bridge Road middle coordinates Bridge Direct intake of noise without shielding Road Bridge definition 17 SoundPLAN's ray tracing procedure finds all geometry in the search direction. For screening and ground absorption, only objects located between the source and the receiver are evaluated. This means that a noise screen with an angled top like in the following picture will not be evaluated for the nearest road because the distance from the screen to the receiver is bigger than from the source to the receiver. dis L s Noise screen with angled top The solution for this situation is in to define a bridge. The command can even be used if the noise wall completely covers the road like a gallery. For a gallery, the screening will be under estimated but the reverberation chamber increases the noise so that the two effects compensate each other for a first order estimate. Gallery As noted above, the conditional bridge commands simulate galleries for a rough estimate. This approach accounts for the direct influence of the sources upon the receiver. Due to reflections between the ceiling and the road, there is a diffuse sound field inside the gallery. The noise from this diffuse scattering must be added to the direct impact. Special Noise Calculation Cases SoundPLAN Manual
