Control transducer locations for virtual acoustic imaging using binaural principle
Takashi Takeuchi, Philip Arthur Nelson · The Journal of the Acoustical Society of America · 2002
When binaural sound signals are presented with loudspeakers, the systems inversion involved gives rise to a number of problems such as loss of dynamic range, deterioration of control performance by small errors, and room reflections. A method of overcoming these fundamental problems is proposed. A conceptual monopole transducer is introduced whose azimuthal position varies continuously as frequency varies. This gives a minimum processing requirement of the binaural signals for the control to be achieved and all the above problems either disappear or are minimized. Among a number of practical solutions to realize such optimally distributed transducers is a discretization that enables the use of conventional transducer units. As for the elevation location of the control transducers, the analysis of the spectral cues and dynamic cues is performed. The frequency response of the plant that relates transducer outputs to ear-pressure signals suggests that control transducer positions will be promising at positions in the frontal plane above the listener’s head. The analysis of the dynamic cues induced by unwanted head rotation also strongly supports the use of transducer locations in the frontal plane. Subjective experiments are performed and the methods described here are proved to be advantageous.