Non-negative surface contributions for cavities based on sound energy density

Abstract

Surface and panel contribution analysis provides a useful methodology to identify sources of radiated sound in cavities. In commercial software, contribution analyses are performed by considering the sound pressure at an internal point. For visualization, a bar chart is usually supplied for the vibrating surfaces. The current solution has two major drawbacks: At first, the traditional technique provides only results for surfaces which are in motion. At second, the sound pressure depends on the location of the field point, which can lead to a deteriorated performance in regions with low pressure values. It is our aim to present non-negative surface contributions for sound energy density in a cavity. Energy-based contributions provide further insight into the characteristics of cavities, as they provide a holistic evaluation of sound pressure and particle velocity. For this, the boundary element method is applied to solve the Helmholtz equation for interior problems. In close analogy to the non-negative intensity, the energy-based contributions are determined from a quadratic form in order to bypass cancellation effects. Results show that regions with high contributions to the energy density are effectively recovered. Some of these surfaces appear almost inactive if the contributions are analyzed only with respect to sound pressure. As such, the evidence from this study suggests that energy-based surface contributions provide an effective quantity to identify sound sources, particularly for regions with low pressure values.