Wen-Chih Wu

Hearing aid system with 3D sound localization

Many people nowadays suffer from various degrees of hearing impairment. Having an appropriate hearing aid system is a good solution to resolve their hearing problem. In this application, various noises interfere with the hearing aid system to result in degrading sound quality. In order to improve sound quality, the schemes to suppress and remove noises are investigated. Additionally, the sound localization that can enhance the perceptual sensation is implemented. In this work, the microphone array and adaptive beam-forming techniques are explored to suppress noises and improve sound quality. Particularly, the time delay of arrival technique for the recorded sound in five microphones is adopted to effectively determine the location of sound. Since the proposed microphone array is worn on the patient chest, the derived sound location need be transferred to the relationship between ears and sound position, in which the head-related transfer function is employed to yield 3D sound. The simulation results show that noises can be suppressed by around 5dB and the sound location can be determined under a 15-degree deviation. Therefore, the proposed hearing aid system can enable persons who have difficulty in hearing to perceive good sound quality and localization.

An analog architecture on parameter estimation of ARMA models

An analog architecture that is suitable for parameter estimation of autoregressive moving average (ARMA) models is proposed. The convergence theorem that connects this architecture with ARMA parameter estimation is presented. Simulation results indicate that its convergence takes only a few microseconds. Hence, this architecture can lead to online implementations. >

Robust echo hiding scheme against pitch-scaling attacks

The pitch scaling conducts serious attacking on audio watermarked signals because it leads to a desynchronization problem. Based on the proposed analysis- by-synthesis echo watermarking scheme, this work develops a watermark extracting process to improve the robustness performance against pitch-scaling attacks. The positions of embedded echoes are altered in the cepstrum domain due to the pitch-scaling attacks that change the frequency content of audio signals. Hence, it is unable to determine the echo position a priori. In this work, the cepstrum values in a reasonable range of delay offsets affected by pitch-scaling attacks are addressed from auditory point of view. The moving average function is performed on several segments to eliminate the impact of host signals on cepstrum. In this extended range for searching delay offsets, the peak value of the cepstrum is adopted to determine the embedded watermark datum. Experimental results exhibit that the proposed robust echo watermarking scheme can be superior to the conventional audio watermarking schemes under pitch-scaling attacks and other attacks.

Analysis-by-Synthesis Echo Hiding Scheme using Frequency Hopping

This work develops an analysis-by-synthesis echo watermarking scheme using frequency hopping to improve robustness and security. First, the host audio signals are transformed and partitioned into several different frequency bands. Each frequency band is then transformed back to the time-domain components that are separated into multiple fractions. Each audio segment is constructed by combining the fractions selected from all frequency bands based on a secret key from a pseudo-noise sequence. The watermarks are embedded in audio segments. In the meantime, the analysis-by-synthesis approach is adopted to perform attacks on the watermarked signals during the watermark embedding process to suggest the adequate amplitudes of echoes. Owing to fractions being scrambled, the chance of watermarks detected and tampered by the third party can be reduced. Additionally, the problem, that it is difficult to correctly embed echoes in long silent intervals, can be overcome by using frequency hopping. Experimental results reveal that the proposed analysis-by-synthesis echo watermarking scheme using frequency hopping can yield better robustness and security than the conventional echo watermarking schemes.

Multiple-sound-source localization scheme based on feedback-architecture source separation

The problem of multiple-sound-source localization in a reverberant environment is investigated in this work, which is a critical technique in video conference applications and is still a challenging task in audio signal processing. In this study, sound signals are first estimated and separated from the mixtures received by a microphone array under a feedback architecture using the blind source separation algorithm. The parameters of time delay of arrival associated with microphones are calculated from the mixtures and estimated source signals by the time-domain cross correlation technique. Finally, the positions of sound sources are derived by the spatial position determination formulas. Experimental results demonstrate that the proposed scheme can effectively determine the locations of multiple sound sources in a near-field and reverberant environment. The direction prediction using the proposed scheme is very promising.

Design and implementation of multi-channel land fowls stunner with current sharing controller

This paper presents an intelligent humane stunner for a multi-channel poultry stunning system with current sharing features. This proposed system consists of an interleaved buck-boost converter for driving the stunning system, a full bridge inverter for generating the stunning voltage, a half bridge inverter for generating dither voltages to expedite the breakdown of skin impedance, and a current sharing controller for providing uniform current to each channel of the stunning system. Hence, the slaughtering quantities of poultry can be increased, and also can reduce poultry stress and improve carcass quality during stunning interval. In this paper, a multi-channel poultry stunning system with ±160V stunning voltage and 320W output power is implemented for verifying its performance. Experimental results shown that the proposed stunning system can raise 10% more coma effectiveness over the one without current sharing algorithm, thus improve carcass quality. Hence, with this approach, fewer components are needed to achieve the better performance, resulting in a multi-channel poultry stunning system with lighter weight and smaller size.