Sound source elevation using spectral notch filtering and directional band boosting in stereo loudspeaker reproduction

In this paper, a virtual elevation method of a sound source is proposed for a stereo loudspeaker reproduction. To achieve this goal, the proposed method first applies a head-related transfer function (HRTF) to the sound source to vertically localize it. Then, spectral notch filtering followed by directional band boosting is used for the further elevation of the sound source. In particular, a filter having three notches is designed by analyzing the spectral characteristics estimated from the measured HRTF database and by investigating the effect of spectral boosting on the perception of sound elevation. To evaluate the elevation performance of the proposed method, subjective listening tests are subsequently conducted using several sound sources, including male and female speech, as well as guitar, violin, and pop music. It is shown from the tests that the sound sources processed by the proposed method are most likely to be perceived as if they are played from stereo loudspeakers located at around 20°, even though the stereo loudspeakers are actually located on a horizontal plane, i.e.,0^o.1.