A study on switching of the transfer functions focusing on sound quality

Many papers have described moving sound image schemes that use loudspeakers or headphones. Since most of these schemes switch the spatial transfer function being used, wave discontinuity occurs at the moment of switching, which degrades the sound quality. While the characteristics of the wave discontinuity depend on the moving sound image scheme used, no paper appears to have considered the relationship between the wave discontinuity and the scheme used. To rectify this omission, this paper examines three approaches: the simple switching approach, the overlap-add approach, and the fade-in·fade-out approach. The sound degradation caused by the wave discontinuity is assessed, and an objective measure, spectrum distortion width, is introduced to quantify the wave discontinuity. Subjective assessments, carried out using Scheffe’s comparison tests, verify that the overlap-add approach with modified hamming window and the fade-in·fade-out approach were better than the other methods.