Sound field reproduction for reduction of pre-echo artifacts based on time-domain weighted least-squares method

Abstract

One of the major problems of sound field reproduction techniques is that by approximating continuous array of loudspeakers to discretely spaced loudspeakers spatial aliasing of driving functions occurs. When spatial aliasing conditions are not satisfied, sound field synthesized to reproduce that of virtual source produces aliasing artifacts in front of the desired wave front, called “pre-echoes”. Pre-echoes become problematic because due to precedence effect, if listener hears pre-echo artifacts first, perception error of virtual sources, such as localization error, and coloration effects occur. A new sound field reproduction method using least-squares method, was suggested by Noh in 2011. The goal of this method is to reproduce target sound field induced by virtual source, using discrete loudspeaker arrays by minimizing sound field error in least-squares sense. Least-squares method is advanta-geous is since this method is a time domain approach, sound field can be weighted spatially and temporally, which can be applied to reduce pre-echo artifacts To verify the suggested method, time domain analysis was performed through numerical simulations. However, due to some assumptions made to derive the cost func-tion and due to the nature of least-squares method, calculated optimal control filter showed high frequency components, and large input, which was impractical in real life. To reduce large input and eliminate high fre-quency components, such constraints was designed and applied to the cost function. These modifications showed that control filter calculated with modified cost function resolved existing problems. Now that means of sound field reproduction technique is modified, temporal and spatial error weighting function was designed to reduce pre-echo artifacts. The error weighting function took form as re-verse of step function, weighing much more to space and time of pre-echo artifact, and less to space and time of target sound field. The cost function was...