A system for controlling the directivity of sound radiated from a structure

Directional sound fields can be generated by arrays of multiple sound sources such as loudspeaker drivers. These systems, though potentially capable of high levels of directivity control over a broad bandwidth, may prove prohibitively expensive, fragile, or impracticable in certain applications. To overcome these limitations, this paper presents an investigation into the design and limitations of a directional structural-actuator-based array. This provides an affordable and robust alternative to conventional loudspeakers, particularly when the actuators can be used to radiate via a pre-existing structure and where the required audio quality is lower, or the bandwidth somewhat limited. In the first instance, an analytical model is formulated and used to perform a simulation-based parametric study, which provides insights into the design trade-offs. Based on this study, a physical prototype is constructed using six actuators and a flat panel, which enables the model to be experimentally validated and an evaluation of the directional radiation capabilities of the proposed system to be carried out. Experiments show that a simple analytical model is an effective tool in designing such arrays, predicting the trends in the behaviour of the prototype and that the structural actuator-based system is capable of controlling directivity within its intended operational bandwidth.