Seigo Enomoto

3-D sound reproduction system for immersive environments based on the boundary surface control principle

We constructed a 3-D sound reproduction system containing a 62-channel loudspeaker array and 70-channel microphone array based on the boundary surface control principle (BoSC). The microphone array can record the volume of the 3-D sound field and the loudspeaker array can accurately recreate it in other locations. Using these systems, we realized immersive acoustic environments similar to cinema or television sound spaces. We also recorded real 3-D acoustic environments, such as an orchestra performance and forest sounds, by using the microphone array. Recreated sound fields were evaluated by demonstration experiments using the 3-D sound field. Subjective assessments of 390 subjects confirm that these systems can achieve high presence for 3-D sound reproduction and provide the listener with deep immersion.

Subjective evaluation of a virtual acoustic system: Trials with three-dimensional sound field reproduced by the “Sound Cask”

It has been necessary to establish subjective measures for the performance of the virtual acoustic systems. In this paper, we report our trials to evaluate the performance of a three-dimensional sound field reproduction system based on the boundary surface control principle, the “Sound Cask.” First, we introduce our investigations for the experts of audio engineering in order to clarify the difference of auditory impression between the Sound Cask and conventional audio systems. Second, we report psychological and physiological experiments focusing on the advantageous points of the Sound Cask, localization performance, and a clear sense of reality, which were pointed out in the investigations for the experts. Finally, we discuss the issues to be considered for subjective evaluation of virtual acoustic systems for future studies.

Providing immersive virtual experience with first-person perspective omnidirectional movies and three dimensional sound field

Providing high immersive feeling to audiences has proceeded with growing up of techniques about video and acoustic medias. In our proposal, we record and reproduce omnidirectional movies captured at a perspective of an actor and three dimensional sound field around him, and try to reproduce more impressive feeling. We propose a sequence of techniques to archive it, including a recording equipment, video and acoustic processing, and a presentation system. Effectiveness and demand of our system has been demonstrated by ordinary people through evaluation experiments.

Application of Three-Dimensional Audio to Copyrighted Multimedia Contents

Copyright is important to protect proprietary properties of multimedia contents, but it possibly poses a challenge in applying complicated signal processing to commercial multimedia products. It is usually forbidden to make a copy of copyrighted materials so that signal processing should be applied on the fly. As a result, such signal processing needs considerable computational costs and requires special devices and software, leading users to hesitate to adopt it. In this article, a method is introduced which enables users to listen to surround sound audio tracks as three-dimensional (3D) audio, without infringement of copyright, with a common multimedia player currently available on a usual PC. The 3D sound can be one that would be heard in an appropriate listening room with a set of ideal loudspeakers, and also can be properly individualized to each listener. Although the method adds a temporal delay in audio contents relative to visual contents, the delay can fall within an acceptable range with respect to the human perception of multimedia contents.

Synthesis of wave front in the sound field recording/reproduction system based on the boundary surface control principle

Based on the boundary surface control (BSC) principle, a new recording/reproduction system is developed to realize high fidelity three-dimensional sound field reproduction. Theoretically, by using this new system, physically faithful reproduction could be achieved in any acoustic environments. Sound recording/reproduction systems based on the BSC principle require many loudspeakers and many microphones. In this new system, the microphone array system to record 3D sound field consists of 70 microphones, and the loudspeaker system to reproduce the recorded 3D sound field consists of 62 full-range units and 8 sub-woofer units. To evaluate the ability of this system, the wave front which is measured in the soundproofed room is compared with the reconstructed wave front within this system. The experiment shows that the reconstructed secondary wave front is very similar to the primary wave front in lower frequency.