Real time calculation of the head related transfer function based on the boundary element method

Presented at the 8th International Conference on Auditory Display (ICAD), Kyoto, Japan, July 2-5, 2002.In order to develop the 3D auditory display using a head phone which allow head movement, real time calculation of the head related transfer function (HRTF) is necessary. In the conventional studies, the calculations are performed approximately based on the mathematical model by regarding the head as the sphere shape. Although the boundary element method is also possible to calculate the transfer function by solving the wave equation from the accurate boundary condition of the head including the shape of the face and the ears measured by the 3D scanner, it is thought to be impossible to calculate it in real time because the amount of the calculation is too big. In this study, we discuss a new calculation method of the HRTF based on the reciprocity principle which enables significant speed-up of the calculation.The demonstrations are available at the website: http://acoust.archi.kyoto-u.ac.jp/HRTF

The superposition principle with regard to the multi-channel adaptive filter

INTERNOISE1998: international congress on noise control engineering, November 16-18, 1998, Christchurch, New Zealand

適応信号処理によるアクティブ吸音装置

An active absorber of sound using an adaptive algorithm is studied. To realize an active sound absorber, the incident wave on the absorber which is usually mixed with the reflected wave, must be known. In conventional methods, in order to separate the incident wave from the reflected wave using two microphones, the delay time during which the sound propagates between the two microphones must be precisely known and the two microphones must have exactly the same sensitivity. We propose two methods using adaptive processing, which do not require such preprocessing for extracting the incident wave : an off-line method using an impulse as a learning signal and an on-line method using sound intensity control. The off-line method, in which the optimum conditions are learned efficiently, yields sound absorption coefficients of more than 99% at low frequencies. In the on-line method, which do not require such learning signals as the off-line method, sound absorption coefficients of more than 95% can be realized at low frequencies

Optimum Arrangement of Secondary Sources and Error Sensors for Active Noise Barrier

INTERNOISE2000: the 29th international congress on noise control engineering, August 27-31, 2000, Nice, France.We have researched on the rational design method of active noise barrier based on the boundary surface control principle. This active noise barrier is composed of a conventional barrier, multiple secondary sources and multiple error sensors. The secondary sources and the error sensors are located on a surface in parallel with the barrier. By using this, we can control noise not only at the error sensor point but also at the other points in a wide area. In this paper, we study on the position of the secondary sources and the error sensors by calculating the control effect using the two-dimensional numerical method. The results show that: (1) the interval between the secondary sources should be less than the half of the wavelength at the frequency considered; and (2) increasing the distance between the error sensor and the secondary source improves effectiveness

A method of designing inverse system for multi-channel sound reproduction-system using least-norm-solution

Active1999: International Symposium on Active Control of Sound and Vibration, December 2-4, 1999, Fort Lauderdale, Florida, US

Robust Sound-Reproduction-System Design Against The Head Movement

WESTPRAC VII 2000: the 7th West Pacific Regional Acoustics Conference, October 3-5, 2000, Kumamoto, Japan.This paper proposes a new sound field reproduction system. Multi-channel sound field reproduction is one of the most promising methods to realize a sound reproduction system robustly against a head movement. Multi-channel sound field reproduction can reproduce the same acoustic field as the recording area by using several controlled points. However, such sound field reproduction systems have not been developed due to poor understanding of the behavior of multiple channel systems. In this paper, we first investigate the accuracy of the reproduced sound of a multi-channel sound reproduction system. In particular we investigate the optimal loudspeaker arrangement and the optimal number of controlled points using computer simulation. We also construct a multi-channel sound field reproduction system which can reproduce the sound within the wide reproduced area around the listener's head. As a result, good sound localization is realized by arranging loudspeakers around the controlled field