Estimation of vibration exposure in residential environments

The University of Salford has derived an exposure-response relationship for vibration in residential environments. Vibration measurements have been used for assessing the human exposure alongside a social study questionnaire based on face-to-face interviews for quantifying the human response. This paper deals with the exposure side of the study. In order to cover the wide range of exposures affecting the living environment, various types of vibration activity have been measured, namely: railway, construction and domestic activity. Different and novel measurement approaches have been adopted for assessing the internal vibration exposure in almost 1,000 dwellings. This paper describes the methodologies used for deriving the est imate of the exposure for each vibration source considered and also provides some results. [Work funded by the Department for Environment, Food and Rural Affairs (Defra) UK] FORMULATION OF THE PROBLEM The exposure is defined as the ̳quantity‘ of vibration to which a hypothetical resident is exposed inside their property from vibration sources that are outside of their control, assuming that they remain indoors during the period of exposure. Different types of vibration may affect a living environment and can be grouped in the following categories (BSI 2008): transient, continuous and random. For providing the wide range of exposure affecting the residential environment, in the framework of the Defra project ―Human Response to Vibration in Residential Environment‖ (Waddington et al. 2011), different vibration sources have been considered, specifically: railway activity, construction activity and internal or domestic activity. In order to develop an exposure-response relationship a high number of case studies are needed. A total of 1,431 case studies were made, including 931 for railway, 350 for construction and 150 for internal vibration sources. In this scenario the living environment has been defined as the dense group of dwellings within a radius of 100 meters from the vibration source for increasing both the range of the exposure and the potential number of respondents. It can be helpful to break down the vibration propagation through the residential environment in 4 areas identified as: source, path, receiver and human body. The vibration perceived by the human body at the ̳point of entry‘ (contact surface between the human body and the vibrating receiver) is due to the complex interaction of the vibration created at the source with the other areas identified above. Each of these regions can amplify or reduce the frequency content of the vibration source. Therefore, these factors need to be taken into account for a complete understanding and estimation of the exposure. Vibration sources can affect the residential environment in a more or less permanent way, like railway traffic, or in a transitory way such as vibration from a construction site. This last characteristic has to be considered in the evaluation of the exposure. As well as potentially affecting the annoyance from vibration it also has major impli10th International Congress on Noise as a Public Health Problem (ICBEN) 2011, London, UK 791 cations for both the measurement and calculation of exposure and in the coordination with the social team in charge of the measurement of response. In order to estimate the exposure from the sources considered in the study different methodologies have been developed. The latter are described in the following section. METHODOLOGIES For evaluating the human exposure, the vibration needs to be considered in the frequency range encompassing the range of human sensitivity. The magnitude and duration of the vibration need to be taken into account and possibly also its temporal characteristic such as repeatability. The vibration exposure is generally quantified with a weighted energy average descriptor such as rms velocity for continuous or random vibration, and for impulsive sources of vibration, peak particle velocity or acceleration is used. However, BS 6472-1 adopts an dose-based exposure metric that can be used for assessing exposure for any type of vibration: the Vibration Dose Value (VDVb/d,day/night).