Masato Nakayama

If we can understand dialogue activities, it will be possible to know the role of each person in the discussion, and it will be possible to provide basic materials for formulating facilitation strategies. This understanding can be expected to be used for business negotiations, group work, active learning, etc. To develop a system that can monitor speech activity over a wide range of areas, we propose a method for detecting multiple acoustic events and localizing sound sources using an asynchronous distributed microphone array arranged in a regular hexagonal repeating structure. In contrast to conventional methods based on sound source direction using triangulation with microphone arrays, we propose a method for detecting acoustic events and determining sound sources from local maximum positions based on estimation of the spatial energy distribution inside the observation space. We evaluated the conventional method and the proposed method in an experimental environment in which a dialogue between two people was simulated under 22,104 conditions by using the sound source signal convolving the measured impulse response.We found that the performance changes depending on the selection of the microphone array used for estimation. Our finding is that it is best to choose five microphone arrays close to the evaluation position.

Wave field synthesis (WFS) can be used to construct virtual sound sources (VSSs) with a loudspeaker array. Conventional methods using a single type of loudspeaker showed limited performance in distance perception. For example, WFS with electro-dynamic loudspeakers (EDLs) has the advantage of constructing VSSs near the loudspeaker, while WFS with parametric array loudspeakers (PALs) has the advantage of constructing VSSs far from the loudspeaker. In this paper, we propose a VSS construction method utilizing crossfade processing with both EDLs and PALs. The contribution of EDLs and PALs was balanced to better synthesize the target sound field. We carried out experiments to evaluate the sound pressure, frequency characteristic, and sound image perception. The experimental results demonstrated that the proposed method can enhance these aspects of the VSS.

Noise reduction methods have been proposed for various loud noises. However, in a quiet indoor environment, even small noises often cause discomfort. One of the small noises that causes discomfort is noise with resonant frequencies. Since resonant frequencies are often high frequencies, it is difficult to apply conventional active noise control methods to them. To solve this problem, we focused on auditory masking, a phenomenon in which synthesized sounds increase the audible threshold. We have performed several studies on reducing discomfort based on auditory masking. However, it was difficult for comfortable sound design to be achieved using the previously proposed methods, even though they were able to reduce feelings of discomfort. Here, we focus on a pleasant sound: music. Comfortable sound design is made possible by introducing music theory into the design of masker signals. In this paper, we therefore propose comfortable sound design based on auditory masking with chord progression and melody generation to match the peak frequencies of dental treatment noises.