Research On Directionality Technology In Digital Hearing Aids

Directionality technology is a key method solving hearing aids users'understanding difficulty under noise environment at present. It includes acoustic source localization and noise source tracking. The available directionality technology in China lacks of accuracy and real-time tracking ability. According to these problems, acoustic source localization methods based on microphones array and a noise tracking algorithm are presented in this paper. An adaptive directionality system is further illustrated.Firstly, this paper deals with time delay estimation algorithms (TDE). The improvements to two classical algorithms are also developed: In order to improve the estimation accuracy and convergence speed of the LMS adaptive filtering time delay estimation algorithm, we propose to utilize a combined filter transfer function to weight the phase data before fitting the phase data to the time delay estimation. For the adaptive eigenvalue decomposition (AED) time delay estimation algorithm, a new version combined with LMS time delay estimation is proposed, which converges more quickly to the new time delay value.Secondly, this paper researches an effective adaptive directionality system. This adaptive directionality system is based on an adaptive combination of two fixed polar patterns that act to make the null of the combined polar pattern of the system output always be toward the direction of the noise, and related adaptive algorithms to update this gain are also given. Theoretical analyses demonstrate its effectiveness and high accuracy.Finally, a novel and effective method for noise tracking based on two microphones array is proposed. This method uses two arrays disposed by 2-D locating to determine the position of noise exciter, and then uses the classic MUSIC algorithm to confirm the noise bearing information in real time. Extended Kalman Filter. (EKF) was employed to track the noise exciter using the above bearing estimation. Simulations show that this method is insensitive to the motions of the target and has the potential for practical applications.