Evaluation of different spatial windows for a multi-channel audio interpolation system

Abstract

The adoption rate of multi-channel audio systems has dramatically increased in recent years. It is common to find 5.1- or 7.1-channel systems in typical home theaters. However, most users do not setup the satellite loudspeakers at the prescribed positions for aesthetic reasons or due to space constraints. Recently, we introduced a technique to optimize multi-channel contents for reproduction over non-ideal loudspeaker setups. Our proposal improves localization accuracy for sound sources reproduced by horizontal loudspeaker arrays. It can also be extended to handle full 3D contents, like those of the upcoming 22.2-channel standard. The proposed method works by applying a set of spatial windows centered at the loudspeaker positions and interpolating along the angles using the spherical harmonics. We now extend our previous results by evaluating the performance of six different spatial window functions. We consider the 5-channel distribution of ITU recommendation BS.775-2, as well as four variations that end-users are likely to deploy. Apparent sound source locations are estimated from the energy and velocity vectors at the sweet spot. Our study found that using the Slepian window with our proposal and a non-ideal loudspeaker layout leads to a reproduced sound field that is closer to that of the ideal configuration.