Topic
Fundamental frequency
About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.
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TL;DR: A pitch measure to detect the harmonic characteristics of voiced sounds on the spectrum of a speech signal and a fast adaptive representation (FAR) algorithm, which reduces the computation complexity of the original algorithm by 50%.
Abstract: 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.
56 citations
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01 Apr 2009TL;DR: In this article, a temporally symmetric voltage waveform is applied to a capacitively coupled radio frequency (CCRF) discharge, that contains one or more even harmonics of the fundamental frequency, the sheaths in front of the two electrodes will necessarily be asymmetric even in a geometrically symmetric discharge.
Abstract: If a temporally symmetric voltage waveform is applied to a capacitively coupled radio frequency (CCRF) discharge, that contains one or more even harmonics of the fundamental frequency, the sheaths in front of the two electrodes will necessarily be asymmetric even in a geometrically symmetric discharge. Optimally this is achieved with a dual-frequency discharge driven at a phase locked fundamental frequency and its second harmonic, e.g. 13.56 MHz and 27.12 MHz. An analytical model, a hybrid ∞uid/Monte-Carlo kinetic model as well as a Particle in Cell (PIC) simulation show that this Electrical Asymmetry Efiect (EAE) leads to the generation of a DC self bias as a function of the phase between the applied voltage harmonics in geometrically symmetric as well as asymmetric discharges. The DC self bias depends almost linearly on the phase angle and the role of the electrodes (powered and grounded) can be reversed. At low pressures the EAE is self-amplifying due to the conservation of ion ∞ux in the sheaths. By tuning the phase, precise and convenient control of the ion energy at the electrodes can be achieved, while the ion ∞ux remains constant. The maximum ion energy can typically be changed by a factor of about three at both electrodes. At the same time the ion ∞ux is constant within §5%.
56 citations
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TL;DR: In this paper, a muffler with an interconnecting hole on the tail pipe was proposed to improve the low-pass filter attenuation performance of low frequency and middle frequency.
56 citations
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TL;DR: In this article, the authors present a method for the maximization of the lowest natural frequency of a structural system of a given weight by varying the stiffness of its component elements, which is based on the Newton-Ralphson method.
Abstract: I integrated structural and mechanical systems, the design criteria may be governed by the fundamental frequency of the structure either to provide a certain precision in control or to prevent damage to the system due to resonance between the mechanical and structural systems. Tracking antennas, radio telescopes, and orbiting reflectors are a few examples of the types of structures for which the frequency consideration becomes exceptionally important. . Turner attempted to minimize the mass of a structure with a specific natural frequency. This problem is governed by a system of nonlinear equations and a solution was obtained iteratively by an adaptation of the Newton-Ralphson method. The procedure consists essentially of starting with a given mass distribution, and hence with a given natural frequency, and then obtaining a series of corrections to the mass distribution until minimum mass is achieved. In many physical problems, the original frequency may not be satisfactory and, hence, the problem of maximization of frequency for a given total mass of the structure becomes important/The objective of this paper is to present a method for the maximization of the lowest natural frequency of a structural system of a given weight by varying the stiffness of its component elements. This problem has been investigated by Taylor for the special case of a bar.
56 citations
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TL;DR: In this paper, the authors investigated the damped vibrational behavior of a lightweight composite plate subjected to a periodic load within a limited time by using the first-order shear deformation theory of plates.
Abstract: This paper investigates damped vibrational behavior of a lightweight sandwich plate subjected to a periodic load within a limited time. The lightweight sandwich structure includes a thick polymeric porous core with either functionally graded or uniformly distributions of voids which is sandwiched by two thin layers of laminate composites. To investigate the effect of void distribution properly, the same void volume fraction has been considered while different types of core have been analyzed. Using the first-order shear deformation theory of plates, the governing equations for the free and forced vibrations have been developed. By involving structural damping, these equations which are able to treat thin to moderately thick plates have been solved by developing a computationally cost-effective finite element approach. An extensive sensitivity analysis has been performed to examine the effects of fiber orientation in composite layers, void’s volume and dispersion in core, and geometrical dimensions on the vibrational behavior of such porous composite sandwich plates (PCSPs). The results show that the use of foam in PCSPs considerably reduces the amplitude of vibrations and improves the fundamental frequency. Furthermore, it was found that the use of [45, −45]2 composite layers offers PCSPs with the highest natural frequency and the lowest amplitude of vibrations.
56 citations