Peter Fiala

Improved Referencing Schemes for 2.5D Wave Field Synthesis Driving Functions

Wave Field Synthesis allows the reconstruction of an arbitrary target sound field within a listening area by using a secondary source contour of spherical monopoles. While phase correct synthesis is ensured over the whole listening area, amplitude deviations are present besides a predefined reference curve. So far, the existence and potential shapes of this reference curve was not extensively discussed in the Wave Field Synthesis literature. This paper introduces improved driving functions for 2.5D Wave Field Synthesis. The novel driving functions allow for the control of the locations of amplitude correct synthesis for arbitrarily shaped—possibly curved—secondary source distributions. This is achieved by deriving an expressive physical interpretation of the stationary phase approximation leading to the presented unified Wave Field Synthesis framework. The improved solutions are better suited for practical applications. Additionally, a consistent classification of existing implicit and explicit 2.5D sound field synthesis solutions as special cases of the unified framework is given.

Wave Field Synthesis of moving sources with arbitrary trajectory and velocity profile

The sound field synthesis of moving sound sources is of great importance when dynamic virtual sound scenes are to be reconstructed. Previous solutions considered only virtual sources moving uniformly along a straight trajectory, synthesized employing a linear loudspeaker array. This article presents the synthesis of point sources following an arbitrary trajectory. Under high-frequency assumptions 2.5D Wave Field Synthesis driving functions are derived for arbitrary shaped secondary source contours by adapting the stationary phase approximation to the dynamic description of sources in motion. It is explained how a referencing function should be chosen in order to optimize the amplitude of synthesis on an arbitrary receiver curve. Finally, a finite difference implementation scheme is considered, making the presented approach suitable for real-time applications.

A parametric study on the isolation of ground‐borne noise and vibrations in a building using a coupled numerical model

Underground traffic induced vibrations and noise in buildings are a major environmental concern in urban areas. To quantify these vibrations a numerical prediction model has been developed and validated. A coupled FE‐BE model is used to compute the incident ground vibrations due to the passage of a train in the tunnel. A dynamic soil‐structure interaction model is used to determine the vibration levels of the building. The soil‐structure interaction problem is solved by means of a 3D boundary element method for the soil coupled to a 3D finite element method for the structural part. An acoustic 3D spectral finite element method is used to predict the acoustic response. The coupled numerical model is used to quantify the efficiency of vibration and noise mitigation measures at different stages of the vibration propagation chain. Vibration isolation with a floating slab track is modeled on the source side, base isolation is incorporated in the structure model, and a box‐within‐box arrangement is considered for the isolation of re‐radiated noise in the buildings rooms. The insertion gain of the three methods is compared using the model of a multi‐story portal frame office building subjected to ground‐borne vibrations from an underground railway line.