Biomedical subjects

Mingsian R Bai

Publications and source records attributed to Mingsian R Bai.

8 recordsLinked to original sources

PubMed2006

Objective and subjective analysis of effects of listening angle on crosstalk cancellation in spatial sound reproduction.

A comprehensive study was conducted to explore the effects of listening angle on crosstalk cancellation in spatial sound reproduction using two-channel stereo systems. The intention is to establish a sustainable configuration of crosstalk cancellation system (CCS) that best reconciles the separation performance and the robustness against lateral head movement, not only in theory but also in practice. Although crosstalk can in principle be suppressed using multichannel inverse filters, the CCS does not lend itself very well to practical application owing to the fact that the sweet spot is being so small. Among the parameters of loudspeaker deployment, span angle is a crucial factor that has a profound impact on the separation performance and sweet spot robustness achievable by the CCS. This paper seeks to pinpoint, from a more comprehensive perspective, the optimal listening angle that best reconciles the robustness and performance of the CCS. Two kinds of definitions of sweet spot are employed for assessment of robustness. In addition to the point source model, head related transfer functions (HRTF) are employed as the plant models in the simulation to emulate more practical localization scenarios such as the high-frequency head shadowing effect. Three span angles including 10, 60, and 120 deg are then compared via objective and subjective experiments. The Friedman test is applied to analyze the data of subjective experiments. The results indicate that not only the CCS performance but also the panning effect and head shadowing will dictate the overall performance and robustness. The 120-deg arrangement performs comparably well as the standard 60-deg arrangement, but is much better than the 10-deg arrangement.

Auditory Perception↗

PubMed2005

Microphone array signal processing with application in three-dimensional spatial hearing.

Microphone arrays are known to enhance the directionality and signal-to-noise ratio (SNR) over single-channel sensors. This is considered beneficial in many applications such as video-conferencing systems and hearing aids. However, this advantage comes at the price of the sensation of spatial hearing. The spatial cues due to diffractions of the head and torso are lost if the array is not fitted in the ears. In this paper we present a system that incorporates binaural hearing synthesis into array signal processing, in an attempt to recover the three-dimensional sound image that a human listener would naturally perceive. In the system, the superdirective beamformer is exploited to estimate the direction of arrival (DOA) of the incoming sound. The spatial sound image is restored by steering the beam to the direction found in the DOA session and filtering the array output with the corresponding Head Related Transfer Functions (HRTF). The algorithms have been implemented in real-time fashion using a digital signal processor. Objective and subjective experiments were performed to validate the proposed system. The experimental results showed that the accurate localization of the sound source is achievable using the array system.

Algorithms↗

PubMed2005

Optimal design of loudspeaker arrays for robust cross-talk cancellation using the Taguchi method and the genetic algorithm.

An optimal design technique of loudspeaker arrays for cross-talk cancellation with application in three-dimensional audio is presented. An array focusing scheme is presented on the basis of the inverse propagation that relates the transducers to a set of chosen control points. Tikhonov regularization is employed in designing the inverse cancellation filters. An extensive analysis is conducted to explore the cancellation performance and robustness issues. To best compromise the performance and robustness of the cross-talk cancellation system, optimal configurations are obtained with the aid of the Taguchi method and the genetic algorithm (GA). The proposed systems are further justified by physical as well as subjective experiments. The results reveal that large number of loudspeakers, closely spaced configuration, and optimal control point design all contribute to the robustness of cross-talk cancellation systems (CCS) against head misalignment.

Algorithms↗

PubMed2003

Optimization and implementation of piezoelectric radiators using the genetic algorithm.

Very thin and small (45 mm x 35 mm x 0.35 mm) piezoelectric radiators have been developed in this research. The system is modeled by using the energy method in conjunction with the assumed-modes method. Electrical system, mechanical system, and acoustic loading have all been accounted for during the modeling stage. On the basis of the simulation model, the genetic algorithm (GA) is employed to optimize the overall configurations for a low resonance frequency and a large gain. The resulting designs are then implemented and evaluated experimentally. Performance indices for the experimental evaluation include the frequency response, the directional response, the sensitivity, and the efficiency. It is found in the experimental results that the piezoelectric radiators are able to produce comparable acoustical output with significantly less electrical input than the voice-coil panel speakers.

Journal Article↗

PubMed2002

Reduction of electronic delay in active noise control systems--a multirate signal processing approach.

Electronic delay has been a critical problem in active noise control (ANC) systems. This is true whether a feedforward structure or a feedback structure is adopted. In particular, excessive delays would create a causality problem in a feedforward ANC system of a finite-length duct. This paper suggests a multirate signal-processing approach for minimizing the electronic delay in the control loop. In this approach, digital controllers are required in decimation and interpolation of discrete-time signals. The computation efficiency is further enhanced by a polyphase method, where the phases of low-pass finite impulse response (FIR) filters must be carefully designed to avoid unnecessary delays. Frequency domain optimization procedures based on H1, H2, and Hinfinity norms, respectively, are utilized in the FIR filter design. The proposed method was implemented by using a floating-point digital signal processor. Experimental results showed that the multirate approach remains effective for suppressing a broadband (200-600 Hz) noise in a duct with a minimum upstream measurement microphone placement of 20 cm.

Electronics↗

PubMed2002

Synthesis of a robust broadband duct ANC system using convex programming approach.

A robust active controller using spatially feedforward structure is proposed for broadband attenuation of noise in ducts. To meet the requirements of performance and robust stability in the presence of plant uncertainties, an H2 cost function and an H(infinity) constrain are employed in the synthesis of the controller. The design is then converted into a convex programming problem using Q-parametrization and frequency discretization. An optimal controller that satisfies the quadratic cost functions and linear inequality constraints can be found by sequential quadratic programming. The optimal controller was implemented via a digital signal processor (DSP) and verified by experiments. Experiment results showed that the system attained 16.5 dB maximal attenuation and 5.9 dB total attenuation in the frequency band 200-600 Hz.

Journal Article↗

PubMed2002

Estimation of sound power of baffled planar sources using radiation matrices.

A technique is presented in this paper for the analysis of acoustic radiation of baffled planar sources. This method is based on the concept of the radiation matrix which is a representation of the sound field radiated by complex sources. Both sound power and far-field pressure can be estimated using this method. Numerical simulation and experimental investigation were carried out to verify the proposed method. In comparison with the conventional pressure-based method ISO 3745, the proposed technique produced more accurate estimation of sound power. With comparable number of measuring positions as the conventional methods, the proposed approach does not require special measuring environments. Computation complexity can be significantly reduced if only dominant radiation modes in the low-frequency range are retained. Estimation of far-field pressure can also be obtained using the proposed method.

Journal Article↗

PubMed2002

Optimal design of panel speaker array with omnidirectional characteristics.

A panel speaker system intended for a projection screen is developed. Like other sound sources with large dimension, the panel speaker has a beaming problem in high frequencies. To alleviate the problem, panel speakers are integrated into an array, with optimal electronic compensation for omnidirectional response and array efficiency. The heart of the design procedure is a three-stage optimization scheme involving two nonlinear and nonconvex objectives. The process is interactive, allowing the array coefficients to be tailored so that the specifications of directional response can be met. The optimal design of panel speaker array is then implemented by using a multichannel digital signal processor. In addition, a Hilbert transformer is required to produce the quadrature components of the array coefficients. A small array and a large matrix were constructed to validate the implemented array signal processing system. The experimental results indicate that, without degradation of efficiency, the proposed optimization technique in conjunction with electronic compensation is effective in attaining omnidirectional radiation property.

Amplifiers, Electronic↗