Sound field reproduction by using an array of loudspeakers

Abstract

This study proposes methods to reproduce a sound field in a selected control region using an array of loudspeakers both temporally and spatially. The sound field that we desire to reproduce is that used for special effects in movies and computer games, or that in real life, i.e., concert halls and stadiums. The desired field is composed of sound waves that come into the control region from outside the region. If we can generate a sound field that is identical to the desired field using an array of loudspeakers, the experience of a listener in the field will be identical to that of the listener in the desired field. In other words, this study aims to mimic the desired field in a control region so as to make listeners feel as if they were in the desired field. This study divides sound field reproduction into the two categories of rendering and duplication according to the desired field. First, if the desired field is used for special effects in movies or computer games, it can be regarded as given. Thus, the problem is reduced to a problem of generating an arbitrary incident wave because the desired field is a superposition of incident waves. This problem is defined as a rendering problem, the aim of which is to generate an arbitrary sound wave and then create a virtual sound source. On the other hand, if the desired field actually exists, it is not regarded as given. Hence this problem contains not only a generation problem, but also a measurement problem. The measurement problem involves measuring the desired field, and an important issue related to this is to devise a method that reduces the number of microphones. The generation problem involves developing a method to generate the reproduced field. It is therefore reduced to a problem of determining the input signals that is fed into the loudspeakers. As a rendering method, a method has been proposed that concentrates sound energy at a point in the wave number domain. Based on this previous method, the prese...