Author(s)

P Santos & A Tadeu

Abstract

The Boundary Elements Method (BEM) is used to compute the sound insulation provided at low frequencies by an elastic wall that divides an air-filled tunnel. In the simulated model, a 3D source is placed in one section of the tunnel, while the response (acoustic pressure) is computed inside both tunnel sections. The BEM is formulated in the frequency domain. The insulation conferred by the wall is characterised, identifying the location of insulation dips in the frequency domain with those dips related to both its own natural dynamic vibration modes and those related to the natural vibration modes of the tunnel. This method models the surfaces of the tunnel and the separating wall completely, and takes full account of the coupling between the fluid (air) and the elastic medium. This model is also used to assess how the dimension of the rooms, the rigidity and thickness of the wall affect acoustic insulation. The transmission loss results obtained via the BEM are then compared with those provided by simplified analytical models such as the Mass Law.

Keywords