This paper describes a 3-stage technique to model the propagation to the far field of nonlinear shock waves produced by high-energy explosive sources. The stages are: (1) a 3-dimensional unsteady Euler method for the strong shock near the source, including a Flux-Corrected-Transport (FCT) method, (2) the Nonlinear Progressive-wave Equation (NPE) procedure for the degeneration of the shock into a linear acoustical wave, and (3) the Parabolic Equation (PE) method for propagation to the far field. Comparisons of calculated data with a linear analytical method are shown. © 2005 Institute of Noise Control Engineering.

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A model based monitoring system is applied on a local scale in an urban area to obtain a better understanding of the traffic noise situation. The system consists of a scalable sensor network and an engineering model. A better understanding is needed to take appropriate and cost efficient measures, especially when changes to the local infrastructure are proposed. The monitoring system provides information about the sound level distribution in the area in time and place. This can be used to create dynamic noise maps or to characterize the soundscape in the area. Results of a field test of two weeks in an urban area of 400 by 200 m are used. Three different areas are considered: (1) the main road which is the major source for traffic noise, (2) a quiet street, and (3) a quiet courtyard. The noise level measurements near the main road are compared with the engineering model results. Next, with the use of actual source levels from the measurements, the sound levels in the quiet street and the quiet courtyard are calculated. By comparing the model results with measurements in these areas, the parameters in the model are updated to better reflect the actual situation.

At military training areas events are created that can be heard kilometers away. The noise levels are subject to variation, mostly due to changes in meteorological conditions. The variation of these events is of importance for environmental noise assessment. Results are presented on the design of a system that automatically detects and localizes these events. It is based on a coarse grid of measurement units that detect relevant acoustic events within the training area. The locations of the events are obtained with a time difference of arrival method and detections from multiple measurement units, including dynamic corrections for meteorological effects. The performance of the system is evaluated with a large set of augmented audio files for different ranges. This set is based on a collection of source measurements of several heavy weapon types. A model that includes the attenuation due to ground and the meteorology is used to extrapolate the audio to more distant locations. The audio is also mixed with relevant background noise for a broad range of wind speeds. With the obtained detection and localization information it is possible to estimate the source levels of events and to extrapolate the measured sound levels to other locations of interest.

The noise reduction of a (low) barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. A so-called Whiswall or WHIStop deflects sound upwards for specific frequencies. Measurements for a 1.1 meter high Whiswall and for a 1.1m barrier are compared in a separate paper. The enhanced barrier effect is measured at a short distance behind the barrier, for several situations. In this paper these measurements are compared with the results of a numerical finite element model (FEM) to validate this model. Next, the noise reduction is calculated at long ranges, up to 600 meters, for different point-to-point scenarios representative for road and rail traffic. A numerical parabolic equation method (PE) is coupled to the FEM model and a representative downwind condition is taken into account. The results at longer distance are used to design an engineering method for the enhanced barrier effect that can be used in standard noise calculation models, such as the Dutch national calculation model (SRM2) or the ISO 9613-2 standard.