Fundamental frequency

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

Determination of Synchronous Machine Electrical Characteristics by Test

Abstract: A method of obtaining synchronous machine d and q axis impedances by test as function of frequency of d, q components is presented. The test involves running the machine at reduced speeds, with a line-to-line short circuit between phases, and temporarily applying excitation to produce line-to-line short circuit current at fundamental frequency corresponding to the particular running speed. Records of line-to-line voltages and short circuit current, along with measurement of rotor angle, are processed to yield d and q components of voltages, currents and flux linkages which turn out to be periodic functions of the fundamental frequency plus harmonics. Straight forward Fourier analysis yields the complex values of operational inductances or impedances L d (j2?), L q (j2?), Z d (j2?) or Z g (j2?) where ?is equal to the speed of the machine at which the tests are conducted.

Real time analysis of voiced sounds

Abstract: A power spectrum analysis of the harmonic content of a voiced sound signal is conducted in real time by phase-lock-loop tracking of the fundamental frequency, fo, of the signal and successive harmonics hl through hn of the fundamental frequency, measuring the quadrature power and phase of each frequency tracked, differentiating the power measurements of the harmonics in adjacent pairs and analyzing successive differentials to determine peak power points in the power spectrum for display or use in analysis of voiced sound, such as for voice recognition.

Striate cortex responses to periodic patterns with and without the fundamental harmonics.

Abstract: 1. The visual system has been modelled as a set of independent linear channels each tuned to a limited band of spatial frequency with the average bandwidth being approximately 1 octave. A great deal of psychophysical and physiological evidence supports this basic notion. However, Henning, Hertz & Broadbent (1975) have shown reciprocal masking between a fundamental frequency (1F) and a complex grating composed of higher harmonics several octaves removed ((4+5+6)F); their results clearly indicate a lack of independence. 2. We recorded the activity of cells in the striate cortex of monkeys and cats using stimuli similar to those of Henning et al. to make comparisons with their psychophysical data and to test specific physiological predictions. 3. We found that cells tuned to the fundamental frequency did not produce an excitatory response to the (4+5+6)F pattern. However, the response of such cells to 1F could be reduced by simultaneous presentation of (4+5+6)F. Similarly, the response of cells tuned to high frequencies, when presented with (4+5+6)F, was reduced by simultaneous presentation of 1F. However, this reciprocal inhibition could be produced between single harmonics (e.g. 1F and 4F) and was not dependent upon a special relationship between 1F and (4+5+6)F. 4. When cells tuned to high frequencies were presented with the (4+5+6)F pattern they generated predictable responses in the higher harmonics (4, 5, 6) but they also generated an unexpected, non-linear, response at the fundamental frequency, 1F, even though no such low frequency component was present in the stimulus. This effect is due to the response rectification which striate cells show. 5. In support of the linear independent spatial frequency channel model, we find (a) striate cells provide an excitatory response to only a limited range of frequencies, (b) they do not provide such responses to the `apparent' yet `missing' fundamental in the (4+5+6)F beating pattern, and (c) the response wave form to complex stimuli like (4+5+6)F is reasonably predictable (at least for simple cells) from the model. Against the model we find that (a) frequencies outside the excitatory bandpass can produce inhibition and (b) the rectification of the response wave form introduces harmonics not present in the stimulus.

Event-based method for instantaneous fundamental frequency estimation from voiced speech based on eigenvalue decomposition of the Hankel matrix

Abstract: We propose a robust event-based method for estimation of the instantaneous fundamental frequency of a voiced speech signal. The amplitude and frequency modulated (AM-FM) signal model of voiced speech in the low frequency range (LFR) indicates the presence of energy only around its instantaneous fundamental frequency (F0) and its few harmonics. The time-varying F0 component of a voiced speech signal is extracted by a robust algorithm which iteratively performs eigenvalue decomposition (EVD) of the Hankel matrix, initially constructed from samples of the LFR filtered voiced speech signal. The negative cycles of the extracted time-varying F0 component provide a reliable coarse estimate of intervals where glottal closure instants (GCIs) may be present. The negative cycles of the LFR filtered voiced speech signal occurring within these intervals are isolated. There is a sudden decrease in the glottal impedance at GCIs resulting in high signal strength. Therefore, GCIs are detected as local minima in the derivative of the falling edges of the isolated negative cycles of the LFR filtered voiced speech signal, followed by a selection criterion to discard false GCI candidates. The instantaneous F0 is estimated as the inverse of the time interval between two consecutive GCIs. Experiments were performed on the Keele and CSTR speech databases in white and babble noise environments at various levels of degradation to assess the performance of the proposed method. The proposed method substantially reduces the gross F0 estimation errors in comparison to some state of the art methods.

Hybrid Synchronous/Stationary Reference-Frame-Filtering-Based PLL

Abstract: Designing an effective phase-locked loop (PLL) for three-phase applications is the objective of this paper. The designed PLL structure is able to provide an accurate estimation of the grid voltage frequency and the phase, even in the presence of all harmonic components of both positive and negative sequences and the dc offset in its input. In addition to offering a high disturbance rejection capability, the suggested PLL structure has a fast transient response and provides a settling time of around two cycles of the fundamental frequency. The effectiveness of the suggested PLL structure is confirmed using numerical results.