The failure of traditional traffic noise control for quiet areas

One can consider the acoustic soundscape as consisting of two parts the direct acoustic soundscape and the diffuse acoustic soundscape. This fact has important consequences when attempting to change the acoustic soundscapes. The traditional approach to control traffic noise by means of noise barriers or change of traffic distribution is only valid for the areas directly exposed from sources (direct acoustic soundscape). These areas will experience a certain decrease of sound pressure levels when applying these noise control measures. However there will be a lower limit for reduction due to the presence of a diffuse acoustic soundscape. To control/modify such a diffuse acoustic soundscape has been shown very difficult by traditional means of noise control. Main characteristic of diffuse acoustic soundscapes is the presence of a multitude of sources, distributed over a wide area contributing evenly to the acoustic soundscape in a certain areas. Screening will only lead to a redistribution of sound, however consequences of such a redistribution will not be recognised in a diffuse sound field. Absorption has been identified as a main parameter to control diffuse acoustic soundscapes. Reducing sound pressure levels in shielded areas such as inner-yards can only be achieved by adding acoustically absorbing areas along the transfer path between source and receiver, but especially inside the inner-yard. Redistribution of traffic flow has been shown to have a tremendous effect on the directly exposed side, but only a small effect in shielded areas

Visualisation of traffic noise exposure and health impact in a 3D urban environment

It is becoming increasingly common to work with urban planning using 3D visualisation tools. In the project DemoVirPEN a research team with participation from different research fields cooperated to create a demonstration concept for visualising traffic noise and the associated health impact in a 3D graphics environment. The project included participation from the following fields; 3D modelling and mapping, traffic noise calculation, auralisation, urban planning and architecture and health impact of noise exposure. The final product of the project is summarised in a film clip that illustrates the main results by visualising and auralising traffic in different configurations from different perspectives. A few key points are visualising short time frames (single vehicle passage) versus yearly average (noise map), and impact of changes such as removing or modifying traffic flows and buildings

An urban planning tool demonstrator with auralisation and visualisation of the sound environment

The paper presents findings from a recent project about the development of a demonstrator of an urban planning tool that includes auralised sounds as well as visualisations of sound propagation and facade noise levels linked to health impact. In urban development projects, the sound environment is one of the key elements, but often enters late in the planning process. As a result, even if the noise regulations are fulfilled, the potentially good sound environment may suffer unnecessary quality reductions. In addition, the standard ways of presenting and analysing the situations, using noise levels and noise maps, has potential for improvement, especially considering the transdisciplinary approaches to planning that are increasing in use. The tool aims to simplify the usage also at early stage planning, including scenario analysis, as well as to facilitate the urban planners\u27 understanding of the sound environment and its effects. The paper presents results from the development of the demonstrator, reflecting on auralisation as well as on multiple aspects of visualisation including grid noise maps, health-related facade noise levels and choice of colour scales

Prediction of Traffic Noise Shielding by City Street Canyons

Reducing the sound level on the exposed building facades due to traffic noise in cities is difficult and expensive. Creating access for the inhabitants to a quiet side can be an alternative method for reducing the annoyance. Therefore it is of interest to predict the level on shielded positions such as courtyards. This is however difficult using traditional methods. Distant sources contribute to the level, and multiple reflections can be very important. The equivalent sources method is used here to make predictions for canyon-like geometries. This method is extended to include effects of diffusion, absorption and atmospheric turbulence in order to improve the predictions. Substantial decreases on quiet side sound levels have been shown when introducing absorption and diffusion, and small increases have been shown due to turbulence. Measurements indicate that the level is relatively constant for courtyards throughout a city area, and a very simple model called the flat city model is proposed to explain this effect. This model assumes that all sources and receivers are located on a flat rigid plane. The effect of shielding by buildings is introduced as a correction term determined from measurements, and this term is within a relatively small range (6-10 dB) for all the areas studied

Prediction of Traffic Noise Shielding by City Street Canyons

Reducing the sound level on the exposed building facades due to traffic noise in cities is difficult and expensive. Creating access for the inhabitants to a quiet side can be an alternative method for reducing the annoyance. Therefore it is of interest to predict the level on shielded positions such as courtyards. This is however difficult using traditional methods. Distant sources contribute to the level, and multiple reflections can be very important. The equivalent sources method is used here to make predictions for canyon-like geometries. This method is extended to include effects of diffusion, absorption and atmospheric turbulence in order to improve the predictions. Substantial decreases on quiet side sound levels have been shown when introducing absorption and diffusion, and small increases have been shown due to turbulence. Measurements indicate that the level is relatively constant for courtyards throughout a city area, and a very simple model called the flat city model is proposed to explain this effect. This model assumes that all sources and receivers are located on a flat rigid plane. The effect of shielding by buildings is introduced as a correction term determined from measurements, and this term is within a relatively small range (6-10 dB) for all the areas studied