Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Effects of the pattern of spectral spacing on the perceptual fusion of harmonics

Abstract: Harmonic relations are important in the perceptual fusion of frequency components, but other factors can influence how much any given harmonic is integrated into a complex tone. This study considers whether the pattern of spectral spacing can act as such a factor. A complex tone consisting only of odd‐numbered harmonics has a regular harmonic spacing of twice the fundamental frequency. The addition of a single even‐numbered harmonic will locally disrupt this regular pattern. If harmonic relations alone limit the perceptual integration of the added harmonic, it should be as well integrated into the complex as its odd‐numbered neighbors. Subjects were required to ‘‘hear out’’ one of the components of the complex and either to rate its perceived clarity (experiment 1) or to judge its pitch in relation to a pure tone 6% higher or lower in frequency (experiment 2). For a fundamental of 100 or 200 Hz, but not 400 Hz, the even harmonic generally could be heard out more easily than its odd neighbors. It is proposed that the poorer integration of the even harmonic at low fundamentals may result from a cross‐channel comparison of amplitude‐modulation rates at the output of the auditory filterbank.

A Digital Signal Processor Based Performance Evaluation of Three-phase Four-wire Shunt Active Filter for Harmonic Elimination, Reactive Power Compensation, and Balancing of Non-linear Loads under Non-ideal Mains Voltages

Abstract: Shunt active power filters are the most viable solution for solving current harmonic, reactive power compensation, and load unbalancing problems widely presented in electrical distribution systems. In this article, development and implementation of a digital signal processor based three-phase four-wire shunt active power filter are analyzed to compensate non-linear and unbalanced loads under non-ideal supply voltages conditions. The proposed algorithm is divided into two parts, the first associated with the calculation of the positive-sequence component of unbalanced supply voltage and second deriving a simple and attractive fundamental extraction filter to extract the fundamental frequency component from distorted positive-sequence voltage. Average power and DC-link energy balance methods are used to calculate peak value of the supply current, which is required to flow from source to load. The behavior and effectiveness of the proposed control algorithm has been verified by simulation using MATL...

Simultaneous observation of fundamental and second harmonic radio emission from the terrestrial foreshock

Abstract: There have been many reports of the terrestrial foreshock as a source of freely propagating electromagnetic (em) radiation1–7, identified as plasma emission at twice the solar-wind plasma frequency, 2fp The 2fp source is close behind the curved surface defined by the interplanetary magnetic field lines tangent to the Earth's bow shock Electrons accelerated at the shock over a wide range of energies propagate along these field lines where, from a time-of-flight effect6, they have a distribution that is unstable to the production of Langmuir waves6,8 These Langmuir waves9,10 and the unstable electron distributions11,12 have been observed The mechanism suggested for generating the 2fp radiation5,6,13,14 by the terrestrial foreshock is closely related to present models of type III solar radio emission and rely on some of the energy in the Langmuir waves converting to em waves The em emission of type III bursts is known to be produced in the solar wind at both the fundamental and second harmonic15, and whether fundamental emission is produced in the terrestrial foreshock is of considerable interest Comparison of nearby fundamental and harmonic emissions and the Langmuir wave energy density in the source will help discriminate between the different conversion models8,14,16 We present here unambiguous measurements made with the sounder experiment aboard the International Sun–Earth Explorer-1 (ISEE-1) and the radio experiment on ISEE-3 of simultaneous fundamental and second harmonic em emission from the Earth's foreshock

Fundamental Frequency of Tapered Plates by Differential Quadrature

Abstract: In this paper, a differential quadrature method is presented for computation of the fundamental frequency of a thin rectangular isotropic elastic plate with variable thickness. In this method, a partial derivative of a function with respect to a space variable at a discrete point is approximated as a weighted linear sum of the function values at all discrete points in the region of that variable. The weighting coefficients are treated as the unknowns. Applying this concept to each partial derivative of the free vibration differential equation of motion of the plate gives a set of linear simultaneous equations, which are solved for the unknown weightage coefficients by accounting for the boundary conditions. The method is used to evaluate the fundamental frequency of linearly tapered plates with simply supported, fully clamped, and mixed boundary conditions. Results are compared with existing solutions available from other analytical and numerical methods. The method presented gives accurate results and is...