Maximization of the directivity ratio with the desired audible gain level for broadband design of near field loudspeaker arrays

This paper mainly addresses design methods for near field loudspeaker arrays. These methods have been studied recently since they can be used to realize a personal audio space without the use of headphones. From a practical view point, they can also be used to form a directional sound beam within a short distance from the sources especially using a linear loudspeaker array. In this regard, we re-analyzed the previous near field beamforming methods in order to obtain a comprehensive near field beamforming formulation. Broadband directivity control is proposed for multi-objective optimization, which maximizes the directivity with the desired gain, where both the directivity and the gain are commonly used array performance measures. This method of control aims to form a directive sound beam within a short distance while widening the frequency range of the beamforming. Simulation and experimental results demonstrate that broadband directivity control achieves higher directivity and gain over our whole frequency range of interest compared with previous beamforming methods.