Browsing by Author "Liu, DJ"

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A neural fuzzy network for word information processing
(2002-04-01)
Lin, CT
;
Duh, FB
;
Liu, DJ
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A neural fuzzy system learning with fuzzy training data is proposed in this study. The system is able to process and learn numerical information as well as word information. At first, we propose a basic structure of five-layered neural network for the connectionist realization of a fuzzy inference system. The connectionist structure can house fuzzy logic rules and membership functions for fuzzy inference. The inputs, outputs, and weights of the proposed network can be fuzzy numbers of any shape. Also they can be hybrid of fuzzy numbers and numerical numbers through the use of fuzzy singletons. Based on interval arithmetics, a fuzzy supervised learning algorithm is developed for the proposed system. It extends the normal supervised learning techniques to the learning problems where only word teaching signals are available. The fuzzy supervised learning scheme can train the proposed system with desired fuzzy input-output pairs. An experimental system is constructed to illustrate the performance and applicability of the proposed scheme. (C) 2002 Elsevier Science B.V. All rights reserved.
Fundamental frequency estimation based on the joint time-frequency analysis of harmonic spectral structure
(2001-09-01)
Liu, DJ
;
Lin, CT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose a new scheme to analyze the spectral structure of speech signals for fundamental frequency estimation. First, we propose a pitch measure to detect the harmonic characteristics of voiced sounds on the spectrum of a speech signal. This measure utilizes the properties that there are distinct impulses located at the positions of fundamental frequency and its harmonics, and the energy of voiced sound is dominated by the energy of these distinct harmonic impulses. The spectrum can be obtained by the fast Fourier transform (FFT); however, it may be destroyed when the speech is interfered with by additive noise. To enhance the robustness of the proposed scheme in noisy environments, we apply the joint time-frequency analysis (JTFA) technique to obtain the adaptive representation of the spectrum of speech signals. The adaptive representation can accurately extract important harmonic structure of noisy speech signals at the expense of high computation cost. To solve this problem, we further propose a fast adaptive representation (FAR) algorithm, which reduces the computation complexity of the original algorithm by 50%. The performance of the proposed fundamental-frequency estimation scheme is evaluated on a large database with or without additive noise. The performance is compared to that of other approaches on the same database. The experimental results show that the proposed scheme performs well on clean speech and is robust in noisy environments.
Multiband room effect simulator for 5.1-channel sound system
(2005)
Chung, JF
;
Liu, DJ
;
Lin, CT
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper investigates a new room effect simulator with different quality of audio sound sources for 5.1-channel sound system. The audio effect relates its impulse response with different room-dimension. The multiband equalizer is designed to generate many kinds of music impression. We also modify the mono Dolby surround decoder into a simplified surround decoder so that the stereo room simulator can generate 5.1-channel surround outputs. All experiments are at a sampling rate of 44.1k Hz and 16 bits per sample. By the room effect simulator, we can get a full and a live listening experience.