Papers by Author: Wen Kung Tseng

Abstract: In this paper performance of actively controlling diffuse fields using acoustic pressure minimization has been presented. The technique is -norm acoustic pressure minimization. The theory and simulations of pressure minimization over space and frequency using two-channel and three-channel systems are presented. This paper focuses on diffuse primary fields with two and three secondary sources. A constrained pressure minimization is also introduced in this paper, to control pressure at various spaces and frequencies. The results show that a good attenuation is achieved at the microphone location or desired range over space and frequency using a two-channel system and a three-channel system. Also the shape of the attenuation contour could be controlled using the proposed method in this paper.

Abstract: This paper evaluates the performance of acoustic beam forming using ultrasonic transducers. A directional audible sound can be generated by amplitude-modulating the ultrasound carrier with an audio signal, then transmitting it from an array of ultrasonic transducers. A novel method has been proposed in this paper to control the beam width of the main lobe and the level of the side lobe for the beam pattern by using an optimization technique. Furthermore, the weighting distribution of uniform linear array composed of eight transducers and the effect of different weightings on the spreading angle of the sound beam have been investigated through simulations in this study. The results show that the optimization method proposed in the paper can effectively control the beam width of the main lobe and the level of the side lobe for the audible sound.

Abstract: There are hundreds of accidents every day recorded by government due to the human factor and environmental factor in Taiwan. The accident usually involved the money dispute; therefore the accident appraisal must indicate the bilateral parties’ blame clearly: all blame; major blame; minor blame and none blame. Although the local police can give a preliminary analysis report at first, the report cannot be official evidence. If the people need a credible appraisal report, they have to apply for the Taiwan Provincial Government Traffic Accident Investigation Committee’s accident appraisal report. However, applying for Committee’s accident appraisal report will take long time. Therefore, this study employed radial basis function neural network to build an expert system for appraisal of bilateral vehicle accident. The database was built from 307 accident cases in Taiwan from the year of 2004 to 2010. According to Committee’s analysis, there are 30 appraisal basses including 6 environmental basses and 24 vehicle basses chosen to be the input of the expert system. The training data includes three types: 70 cases training; 140 cases training; 207 cases training. Validation stage was carried out by using 100 fixed cases and the correctness was recorded. In the first stage, correctness rate is 76% for training with 70 cases. In the second stage, correctness rate is increased to 81% for training with 140 cases. In the third stage, correctness rate is increased to 89% for training with 207 cases. The training and validation processes were completed in one second. Therefore, the expert system proposed in this work is demonstrated to be an efficient system for the accident appraisal.

Abstract: An expert system has been proposed to estimate the relationship between the vehicle pre-braking speed and the length of the skid mark. Since the length of the skid mark varies with many factors, there is no a single formula or equation which can represent the relationship between the vehicle pre-braking speed and the length of the skid mark. Therefore in this paper an expert system is built to estimate the relationship between the vehicle pre-braking speed and the length of the skid mark. The radial basis function (RBF) neural network is used for the expert system due to its shorter training time and higher accuracy. There are many factors affecting the skid mark. In this paper we choose 7 factors, i.e. brand of vehicle, vehicle displacement, year of manufacture, vehicle weight, vehicles with and without ABS, roadway surface, and vehicle speed for the training in the RBF neural network. The total number of the training data for the RBF neural network is 2619. The results showed that high accuracy is obtained for estimating the relationship between the vehicle pre-braking speed and the length of the skid mark. Thus the expert system proposed in this paper is demonstrated to be a suitable system for estimating the relationship between the vehicle pre-braking speed and the length of the skid mark.

Abstract: In this paper design of quiet zones in broadband diffuse fields has been present by using the method of acoustic pressure minimization over various spaces and frequencies. The technique is squared acoustic pressure minimization. The theory and simulations of pressure minimization over space and frequency using one-channel and two-channel systems are presented. The work presented in this paper focus on diffuse primary fields with one and two secondary sources. It is shown that larger zones of quiet are obtained using two secondary sources, with better control over the shape and location of the quiet zones. The main contributions of the paper are that a design method of active systems to generate larger zones of quiet in broadband diffuse fields is proposed and the performance of the active systems is analyzed.

Abstract: This paper investigates the performance and stability of a virtual microphone feedback controller for local control of sound through theoretical analysis and simulations. A novel method to design a stable feedback controller for the local control system is also presented in this paper. The local control system is designed to attenuate a broadband disturbance at a point near the listener’s ear, i.e. the virtual microphone, rather than at the control microphone, i.e. the physical microphone. The results showed that if a good performance was to be achieved the controller would be unstable. This is because the magnitude of the response of the virtual plant is lower than that of the physical plant. The feedback controller in this work is designed to minimize the noise at the virtual microphone, with a virtual plant response used in the performance objective. However the physical plant is used in the stability constraint. Therefore there is a trade-off between the performance and controller stability.