A Research and Development of an Audio System to Realize Distant Collaborative Learning with Togetherness

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The results are classified roughly and described as follows.(1) The audio system : (i) Recording : Main-lobe-width of microphone array is 30 deg. maximum for directional recording. The optimum arrangement of the microphone array is derived. (ii) Loudspeaker : Flat panel loudspeaker is better to be used which is driven in-phase and has an area of A2 copy paper size or more. (iii) Combination : The microphone array can be attached on the edge of the flat panel loudspeaker where the acoustic feed back is comparatively insignificant and directional pattern of the microphone array can be controlled same as when it is alone. (iv) Transmission channel : Independent 3 or 4 channels are needed for speech transmission to consider two or more speakers speak simultaneously. (v) Signal processing : Dereverberation of the reverberant speech recorded in the classroom can be done by using signal processing technique developed in this study to make speech intelligibility better. (vi) Speaker image : To … More display image of the speaker improves speech intelligibility. (2) Criterion : Evaluation by the psychological scale of "easy aural comprehension" newly proposed in this study is valid to estimate performances of the audio system. The condition, in which two speakers speak simultaneously, used in the experimental examination shows the difference of the performance of the audio system clearly. The acoustic characteristics which bring "feel like in a classroom" or spacious of the room are found and to the contrary those impede them are found. (3) Application of Virtual Reality : To apply the technique of Virtual Reality to distant collaborative learning, [1] a method was found to estimate the temporal change of the room transfer function which helps to reduce the acoustic feed back, [2] approximation method to obtain head related impulse response is found used to create the virtual auditory space. [3] the way to express the sense of healing in the virtual auditory space is found. (4) Patent pending : 3D sound image technique for the flat panel loudspeaker is applied for a patent. It is already introduced into the personal computer made by NEC named "Authen Surround."To conclude, the audio system to realize distant collaborative learning with togetherness can be figured out which validity is supported by the various psychological examinations. Less