Directional Quality of 3-d Amplitude Panned Virtual Sources

When a listener is surrounded by multiple loudspeakers, some of which are located above and/or below him/her, an immersive threedimensional auditory display can be created with vector base amplitude panning (VBAP). In VBAP a complex loudspeaker layout is divided to loudspeaker triplets or pairs (sets). A sound signal is applied to loudspeakers of one set with different gain factors at one time, which creates a virtual source to a direction that does not necessarily correspond with any of the loudspeakers. The directional quality of virtual sources created with VBAP is studied in this paper. Listening tests are conducted with loudspeaker pairs in horizontal and vertical layouts, and with a loudspeaker triplet. The results are interpreted with a binaural model. The binaural model is further used to predict directional quality of virtual sources in arbitrary loudspeaker setups. It is found that VBAP predicts the angle between the median plane and a perceived virtual source quite accurately when the loudspeakers of a set are near the median plane. When loudspeakers are moved to a side of the listener, virtual source direction is biased towards the median plane. The elevation of virtual sources is perceived individually and can not be predicted with any panning law.