Browsing by Author "Wu, JD"

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A ring silencer design for reducing noise of axial fan
(2003-09-01)
Wu, JD
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Bai, MR
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機械工程學系
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Department of Mechanical Engineering
In this paper, a ring silencer design for reducing the noise of axial fans is presented. The noise sources on axial fans are usually caused by the fluctuating pressure distribution on the surface of fan blade. Most of the sources are near the trailing edge of blades or boundary region of blades. The ideation of proposed design is based on the principle of Helmholtz resonator for reducing the noise around the fan. The electro-acoustic analogy of this design is presented and simply discussed. Experimental measurement is carried out to evaluate the proposed design for reducing the axial fan noise. The result of experiment indicated that the ring silencer achieved 17 dB in blade passing frequency and 10 dB in other broadband frequency of power spectrum level.
Background noise cancellation for hands-free communication system of car cabin using adaptive feedforward algorithms
(2003)
Wu, JD
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Lee, TH
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Bai, MSR
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機械工程學系
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Department of Mechanical Engineering
This paper describes the background noise attenuation for hands-free communication systems of car cabins using adaptive feedforward noise control algorithm. For hands-free telephone system, the quality of communication usually is effect by background noise such as engine noise and aerodynamic noise. In the present study, an active noise control (ANC) design for reducing car cabin periodic background noise from engine and broadband random noise using adaptive feedforward control are investigated. The control algorithm is based on the well-known filtered-x least mean square (FXLMS) with multi-sine synthesized reference signal and frequency counting technology is implemented on a digital signal processor (DSP) platform. Experimental results indicated that the proposed design was effective suppressing 15 dB in periodic engine noise and 2-3 dB in broadband random background noise.
Development of a multiple channel active noise cancellation system for car cabins
(2003)
Chen, HH
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Wu, JD
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Bai, MR
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機械工程學系
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Department of Mechanical Engineering
This paper describes the development of a multiple-channel active pp noise cancellation system for car cabins. Various active techniques are compared in terms of control structures and control algorithms. The filtered-x least-mean-square algorithm with synthetic reference and the linear quadratic gaussian control are employed for controller synthesis. Feedback, feedforward and hybrid configurations are adopted as the major control structures. The plant model is identified using a frequency-domain method. The controllers are implemented by using a digital signal processor. Experiments are carried out to evaluate the proposed techniques for attenuation of the internal field in a car cabin. The experimental results indicate that the hybrid control structure yields the best performance in terms of noise attenuation and convergence speed.
Development of a zero spillover controller for broadband cancellation of noise in ducts
(2001-11-01)
Wu, JD
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Bai, MR
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機械工程學系
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Department of Mechanical Engineering
In this paper, an active noise control (ANC) system for broadband cancellation of noise in ducts. where a nonacoustical reference is unavailable and thus the ANC structure is "spatially feedforward" is presented. In this structure, acoustic feedback that is known to be detrimental to system stability and performance must be taken into account in controller design. in this case, difficulties generally arise in implementing the ideal controller. or the zero spillover controller due to plant uncertainties. In the present study, an equivalent approach based on the 2-norm (H-2) optimal model matching principle is proposed in controller design. The control algorithm is implemented on a digital signal processor (DSP). by finite impulse response (FIR), infinite impulse response (IIR) and hybrid filters. The experimental results indicate that the proposed controller was effective in suppressing periodic noise and random noise sources. without and with airflow.
Digital signal processor implementation of active noise control systems for broadband noise cancellation in engine exhaust systems
(2000-08-01)
Wu, JD
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Bai, MR
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機械工程學系
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Department of Mechanical Engineering
This paper describes the principle and application of broadband active noise control (ANC) for engine exhaust systems using a spatially feedforward structure. The algorithm of the proposed controller is obtained from previous work by Roure (1985), Munjal and Eriksson (1988), Hong and Bernstein (1998), and there exist some conclusions for this structure. The self-adaptive broadband controller is discussed and implemented on a digital signal processor (DSP), using finite impulse response (FIR) and infinite impulse response (IIR) filters. Experiments were carried out to evaluate the proposed system for reducing the noise under different engine operating conditions. The experimental results indicate that the ANC system is effective in reducing the broadband noise for engine exhaust systems using the spatially feedforward structure.
Effects of directional microphone and transducer in spatially feedforward active noise control system
(2001-10-01)
Wu, JD
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Bai, MR
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機械工程學系
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Department of Mechanical Engineering
In this paper, an experimental study concerning the effects of a directional microphone and transducer in a duct active noise control (ANC) system in the presence of acoustic feedback is described. In the duct ANC system, a spatial feedforward system is used for broadband noise cancellation in ducts, where a non-acoustical reference is unavailable. In this structure, acoustic feedback that is known to be detrimental to the system stability and performance must be taken into account in the controller design. The algorithm of the proposed control system is based on the previous work by Roure (1985), Munjal and Eriksson, Hong and Bernstein (1998), and there exists some discusses for spatially feedforward structure. The algorithm is implemented on a digital signal processor (DSP), using finite impulse response (FIR) and infinite impulse response (IIR) filters. Experiments are carried out to evaluate the effects of a directional microphone and transducer in proposed the system for reducing the noise at the broadband noise source. The results of the experiment indicated that the proposed system with a directional microphone and loudspeaker improved the ANC system attenuation performance in the presence of acoustic feedback.
SHDS - An X-Window based semi-hypermedia document system
(1996-01-01)
Yuan, SM
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Wu, JD
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Wang, DL
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交大名義發表
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資訊工程學系
The internal structure of hypermedia and the navigation between nodes are always a complex and large problem. Thus, creating and managing a hypermedia document system has become a challenge. The SHDS is a convenient tool that lets users create their own hypermedia documents. The media included in the SHDS are Texts, Sounds and Images. The SHDS provides a graphic browser so that authors and users can realize where they are. Moreover, it uses a special model to group related nodes together so that authors can express a single concept by using multiple objects. In summary, the SHDS provides a lot of flexibility to let authors create their own documents.,