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- Use of vibration measurements to determine the most suitable locations to improve sound insulation in buildingsPublication . Rosão, Vitor; Carreira, A. S.In the present work in situ sound insulation measurements were performed, according to the applicable standards of ISO 140 series, and vibration measurements of the separator elements in question (floor, ceiling, side walls). We intend to compare the results of direct measure-ments of sound insulation with the results of the predictions of sound insulation, based on the vibration measurements, to verify the feasibility of using vibration measurements to determine the most suitable locations of sound propagation (floor, ceiling, side walls) to act in order to improve, where it is needed, sound insulation in buildings. The principles of sound propaga-tion considered in EN 12354 series standards are used, e.g., 5 major structural paths, depend-ing on the sound radiating element in the receiver compartment [1) partition wall, 2) ceiling, 3) floor, 4) wall left side, 5) wall right side] and 2 major airborne path [1) openings in the par-tition element, 2) openings in other elements]. Different Radiation Factors, to convert vibra-tion of elements in sound are also considered, depending on the radiation element type and on the frequency in question.
- Prediction of low frequency sound fields in buildings near railway linesPublication . Neves e Sousa, Albano; Lopes, Isabel; Carreira, A. S.The design of new buildings in the vicinity of railway lines must consider protection against noise and vibrations induced by railway traffic. However, the prediction methods available involve heavy numerical models which have frequency limitations. In this paper a prediction method combining finite elements (FEM) with natural mode analysis is presented for use in reinforced concrete buildings with heavy walls. The method considers 2D FEM models of the railway, ground and buildings to identify the transfer function of vibration from the railway to building foundations. Also 3D models of the buildings are considered to identify the transfer functions of vibration from foundations to walls and floors. Finally, as the impedance of heavy walls and floors is much higher than the acoustic impedance of air, the numerically assessed vibration fields of walls and floors are used to calculate sound fields in rooms by means of natural mode analysis. A set of in situ measurements were made in two different situations in order to calibrate the prediction method and also to identify the factors which most affect vibration and sound transmission.