When an omni-directional loudspeaker is placed close to a surface or surfaces, reflections from the surface(s) can be as dominating as the direct propagating sound, and can thus deteriorate the omni-directionality (as referred to as uniform directionality) of the sound source. This effect can eventually degrade the sound quality because the frequency response is distorted at listening positions. This research is concerned with the sound radiation control for the uniform directionality in the presence of strong early reflections. A circular array of loudspeakers mounted on the surface of a cylinder is employed to apply radiation control methods. It is shown that even when there is a wall close to this array, the directionality can be kept uniform by controlling the radiation as long as the distance to the surface is known. The effects of errors introduced in the distance and the reflection coefficient of the surface are investigated. The results imply that such sound radiation control can improve the uniform directionality and sound quality of loudspeaker arrays with the aid of sensors that can measure distances to surfaces.
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