Optimal source distribution for virtual acoustic imaging
Takashi Takeuchi, Philip A. Nelson · The Journal of the Acoustical Society of America · 2000
When binaural sound signals are presented with loudspeakers, the system inversion involved gives rise to a number of problems such as loss of dynamic range and a lack of robustness to small errors in control performance. Regularization, often used to design practical filters, also results in poor control performance around ill-conditioned frequencies. These problems for such systems are investigated and this has resulted in the proposal of a new system concept. The system overcomes these fundamental problems by means of a conceptual pair of monopole transducers whose span varies continuously as a function of frequency. The underlying theoretical principle is described in detail. The significance is that all of the above problems that are associated with the multi-channel system inversion are solved by using this principle. The limitations with this principle are also made clear in terms of the operational frequency range. Several examples of practical solutions that can realize a variable transducer span by discretization are also described. The discretization expands the operational frequency region to be used with only a little decrease in performance. This principle is extremely useful and practical because a single transducer which can cover the whole audible frequency range is not currently available.