Summary

Our main research topic is “inverse problems for acoustic field” and “signal processing for sound field recording, transmission, and reproduction”. Details are described below.

Inverse problems for acoustic field: We tackle with inverse problems for acoustic field, such as sound field imaging, analysis, source localization, and estimation of room acoustic parameters. We pursuit new methodologies with various approaches (optimization, machine learning, etc.) and develop systems to achieve these purposes.

Signal processing for sound field recording, transmission, and reproduction: We deal with a broad range of problems for sound field recording, transmission, and reproduction. By using these methodologies, we develop new systems for telecommunication, virtual reality, and so on.

Projects

Sound field reproduction using loudspeaker array

Sound field reproduction

Since conventional stereophonic / surround sound systems are based on an auditory property called summing localization, their appropriate listening position is limited to the center of loudspeakers, the so-called sweet spot. Furthermore, especially when reproducing reverberant sounds, the driving signals of the loudspeakers are manually designed by sound engineers. Sound field reproduction techniques aim to synthesize physical acoustic fields, enabling a broad listening area and sound distance and reverberation reproduction without designing processes.

References

  • S. Koyama, K. Furuya, Y. Hiwasaki, and Y. Haneda, "Analytical Approach to Wave Field Reconstruction Filtering in Spatio-Temporal Frequency Domain," IEEE Trans. Audio, Speech, Lang. Process., vol. 21, no. 4, pp. 685-696, 2013.
  • N. Ueno, S. Koyama, and H. Saruwatari, "Three-Dimensional Sound Field Reproduction Based on Weighted Mode-Matching Method," IEEE/ACM Trans. Audio, Speech, Lang. Process., vol. 27, no. 12, pp. 1852-1867, 2019.

Binaural reproduction from microphone array recordings

Binaural reproduction

Binaural reproduction is a spatial audio technology that reproduces sounds at two ear positions by using headphones and head-related transfer functions (HRTFs). The binaural sounds in a VR space are simply reproduced by numerical acoustic simulations using given source positions and signals. However, the binaural reproduction of a real environment is not straightforward. We develop a technology to estimate a sound field using a microphone array and reproduce it as binaural sounds, which can be applied to VR systems requiring a large listening area.

References

  • N. Iijima, S. Koyama, and H. Saruwatari, "Binaural Rendering from Microphone Array Signals of Arbitrary Geometry," J. Acoust. Soc. Amer., vol. 150, no. 4, pp. 2479-2491, 2021.
  • N. Ueno, S. Koyama, and H. Saruwatari, "Sound Field Recording Using Distributed Microphones Based on Harmonic Analysis of Infinite Order," IEEE Signal Process. Lett., vol. 25, no. 1, pp. 135-139, 2018.

Spatial active noise control

Spatial ANC

Active noise control (ANC) is a technique to reduce noise by a canceling loudspeaker and monitoring microphone, which has been applied to local or one-dimensional space such as earphones and air ducts. Spatial ANC aims to reduce noise over a three-dimensional target region. However, conventional techniques can reduce noise only at microphone positions. We develop a new spatial ANC technique to reduce regional noise by estimating a noise field with microphones and synthesizing an anti-noise field with loudspeakers.

References

  • S. Koyama, J. Brunnström, H. Ito, N. Ueno, and H. Saruwatari, "Spatial Active Noise Control Based on Kernel Interpolation of Sound Field," IEEE/ACM Trans. Audio, Speech, Lang. Process., vol. 29, pp. 3052-3063, 2021.
  • H. Ito, S. Koyama, N. Ueno, and H. Saruwatari, "Feedforward Spatial Active Noise Control Based on Kernel Interpolation of Sound Field," in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process. (ICASSP), pp. 511-515, Brighton, May, 2019.

Personal sound zone synthesis by multizone sound field control

Personal sound zone

In a general sound system, sounds spread in all directions; thus, interference of multiple sounds can be noisy, and sounds can be delivered to someone who does not want to hear. Local-field sound reproduction aims to synthesize personalized sound zones by multizone sound field control with multiple loudspeakers.

References

  • S. Koyama, T. Amakasu, N. Ueno, and H. Saruwatari, "Amplitude Matching: Majorization-Minimization Algorithm for Sound Field Control Only With Amplitude Constraint," in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process. (ICASSP), pp. 411-415, Jun., 2021.