In loudspeaker-based 3D audio systems, there are some acoustic crosstalk cancellation methods to enlarge the 'sweet spot' around a fixed listener position. However, these methods have common defect that most of them can be applied only to the specific narrow frequency band. In this letter, we propose the more robust acoustic crosstalk cancellation method so that we can cancel the crosstalk signal in far wider frequency band and enlarge 'sweet spot. ' For this goal, we apply a sum and difference filter to the conventional three loudspeaker-based 3D audio system.

The non-individualized head related transfer function (HRTF) is known to have a few problems, which are referred to as the 'hole in the middle' phenomenon and 'front-back reversals.' To overcome these problems, an HRTF refinement technique was introduced, but unfortunately, this refinement technique causes sudden degradation in sound quality and difficulty in cross-talk cancellation because of notch frequency exaggeration. In this paper, an HRTF refinement using directional weighting function is proposed. This newly proposed technique weights ordinary HRTF according to its direction to amplify frontal sound intensity. Since the proposed technique does not exaggerate the notch frequency, spectral differences in the 'cone-of-confusion' region become more pronounced within overall audible frequencies, resulting in mitigating the sound degradation. In addition, the cross-talk cancellation can be done more easily. We verified the superiority of the proposed technique over the existing one by means of the sound localization and sound quality tests in headphone and loudspeakers.

The measurement of the 3-dimensional behavior of early reflections in a sound field has been an important issue in auditorium acoustics since the reflection profile has been found to be strongly correlated with the subjective responsiveness of a listener. In order to detect the incidence angle and relative amplitude of reflections, a 4-point microphone system has conventionally been used. A new measurement system is proposed in this paper, which has 5 microphones. Microphones are located on each four apex of a tetrahedron and at the center of gravity. Early reflections, including simultaneously incident reflections,which previous 4-point microphone system could not discriminate as individual wavefronts, were successfully found with the new system. In order to calculate accurate image source positions, it is necessary to determine the exact peak positions from measured impulse responses composed of highly deformed and overlapped impulse trains. For this purpose, a peak-detecting algorithm, which finds dominant peaks in the impulse response by an iteration method, is introduced. In this paper, the theoretical background and features of the 5-microphone system are described. Also, some results of experiments using this system are described.