Showing papers on "Fundamental frequency published in 1989"

Method of determining drill bit wear

Abstract: A method is provided for determining the state of wear of a multicone drill bit. Vibrations generated by the working drill bit are detected and converted into a time oscillatory signal from which a frequency spectrum is derived. The periodicity of the frequency spectrum is extracted. The rate of rotation of at least one cone is determined from the periodicity and the state of wear of the drill bit is derived from the rate of cone rotation. The oscillatory signal represents the variation in amplitude of the vertical or torsional force applied to the drill bit. To extract periodicity, a set of harmonics in the frequency spectrum is given prominence by computing the cepstrum of the frequency spectrum or by obtaining an harmonic-enhanced spectrum. The fundamental frequency in the set of harmonics is determined and the rate of cone rotation is derived from the fundamental frequency.

Time evolution from linear to nonlinear stages in magnetohydrodynamic parametric instabilities

Abstract: The nonlinear evolution of the magnetohydrodynamic (MHD) parametric instability of wave fluctuations propagating along an unperturbed magnetic field is investigated. Both a magnetohydrodynamic perturbation‐theoretical approach and a nonlinear MHD simulation are used. It is shown that high harmonic waves are rapidly excited by wave–wave coupling, and that the wave spectrum evolves from a state containing a small number of degrees of freedom in k space to one which contains a large number of degrees of freedom. It is found that the spectral evolution prior to nonlinear saturation is well described by the perturbation theory. During this stage, the ratio of the growth rate of the nth harmonic wave to the linear growth rate of the fundamental wave is n. The nonlinear saturation stage is characterized by a frequency shift of the fundamental wave that destroys the wave–wave resonance condition which, in turn, causes the wave amplitude to cease its growth.

Applications of fast orthogonal search: time-series analysis and resolution of signals in noise.

Abstract: In this paper a technique is examined for obtaining accurate and parsimonious sinusoidal series representations of biological time-series data, and for resolving sinusoidal signals in noise. The technique operates via a fast orthogonal search method discussed in the paper, and achieves economy of representation by finding the most significant sinusoidal frequencies first, in a least squares fit sense. Another reason for the parsimony in representation is that the identified sinusoidal series model is not restricted to frequencies which are commensurate or integral multiples of the fundamental frequency corresponding to the record length. Biological applications relate to spectral analysis of noisy time-series data such as EEG, ECG, EMG, EOG, and to speech analysis. Simulations are provided to demonstrate precise detection of component frequencies and weights in short data records, coping with missing or unequally spaced data, and recovery of signals heavily contaminated with noise. The technique is also shown to be capable of higher frequency resolution than is achievable by conventional Fourier series analysis.

Method and apparatus for improving performance of AC machines

Abstract: A method and apparatus for improving the performance of polyphase AC machines. The polyphase AC machines are excited both with a fundamental frequency and with an odd harmonic of the fundamental frequency. The fundamental flux wave and the harmonic flux wave will travel at synchronous speed in the air gap. This facilitates redistributing the flux densities in the machine and thereby increasing the total flux per pole in the machine.

The Effect of the Heartbeat on Vocal Fundamental Frequency Perturbation

Abstract: Signal-averaging and autocorrelation analysis revealed that the cardiovascular system exerts a modest but consistent influence on vocal fundamental frequency (F0), accounting for approximately 0.5%...

Perceptual grouping of formants with static and dynamic differences in fundamental frequency

Abstract: The perceptual consequences of exciting one formant (F2 or F4) of a composite syllable with a different fundamental from the others were examined in experiment 1 using a four‐formant syllable for which F1, F2, and F3 give /ru/ and F1, F3, and F4 give /li/. When all four formants are on the same fundamental, the percept is /ru/, but exciting F2 on a sufficiently different fundamental gave predominantly /li/ percepts. Smaller differences in fundamental left the phonetic percept unchanged but made F2 stand out as a separate sound source. Exciting F4 on a different fundamental also made it stand out as a separate sound source, though larger differences in fundamental were needed than for F2. Experiment 2 replicated these static effects of fundamental frequency differences on F2, but failed to find any substantial effect of coherent or incoherent fundamental frequency modulation functions on perceptual grouping or separation. Although static differences in fundamental frequency exert a strong effect on the perceptual grouping of formants both in terms of the number of sound sources heard and the perceived phonetic category, the coherence of fundamental frequency movement has almost no independent effect on the perceptual grouping of formants.

Efficient large-signal FET parameter extraction using harmonics

Abstract: An accurate and truly nonlinear large-signal parameter extraction approach is presented, using not only DC bias and fundamental frequency but also higher harmonic responses. The harmonic balance method for nonlinear circuit simulation, adjoint analysis for nonlinear circuit sensitivity calculation, and state-of-the-art optimization methods are applied. Improvements to the convergence of the optimization process are discussed. An automatic weight assignment algorithm enhancing parameter extraction is given. Numerical results demonstrate that the method is both theoretically and computationally feasible, i.e. it can uniquely and efficiently determined the parameters of the nonlinear elements of the GaAs MESFET model under actual large-signal operating conditions. Numerical results also show that under multibias, multipower inputs, and multifrequency excitations, spectrum measurements can effectively reflect the nonlinearities of the model and improve model reliability when they are used in nonlinear large-signal-model parameter extraction. >

Impact of cycloconverter harmonics

Abstract: Findings from a study on the harmonics generated by a 15 MVA three-phase 13.2 kV 60 Hz to single-phase 24/12 kV 25 Hz static frequency converter (SFC) or cycloconverter are summarized. At light loads, some of the characteristic harmonics (e.g. 10 Hz, 110 Hz) have magnitudes that exceed the fundamental frequency. Since the three-phase components at these frequencies do not necessarily nullify each other, many frequency components, in addition to zero-sequence components, can be measured in the neutral (residual) current. Because of low system impedance at harmonic frequencies, the voltage at the 13.2 kV substation supplying the SFC is not severely affected. A worst-case scenario for the voltage spectrum is presented. The corresponding distortion factor is calculated to be 4.12%. The power factor of an assumed parallel load is calculated using this scenario, and the effect of the SFC harmonics on the power factor is found to be insignificant. However, depending on the system impedances, the shunt capacitors for power factor compensation at the assumed load may be ineffective due to harmonic resonance. >

Nonlinearly generated spectral components in the nearfield of a directive sound source

Abstract: Nonlinear propagation of sound waves generated by a directive ultrasound source in air is discussed theoretically and experimentally. The circular source of 21 cm in radius consists of 1410 small PZT bimorph transducers, whose resonance frequency is 28 kHz. For a single‐frequency wave excitation, sound pressures of the fundamental, second, and third harmonics are measured and are compared with the numerical results using a method of Aanonsen et al. [J. Acoust. Soc. Am. 75, 749–768 (1984)]. Extending their initial condition to the case of a two‐frequency wave excitation, propagation curves and beam patterns of the difference frequency sound are obtained and compared with the measured data. All observations quantitatively agree very well with the numerical calculation. Nonlinear attenuation of spectral components by increasing the source pressure is clearly confirmed.Nonlinear propagation of sound waves generated by a directive ultrasound source in air is discussed theoretically and experimentally. The circular source of 21 cm in radius consists of 1410 small PZT bimorph transducers, whose resonance frequency is 28 kHz. For a single‐frequency wave excitation, sound pressures of the fundamental, second, and third harmonics are measured and are compared with the numerical results using a method of Aanonsen et al. [J. Acoust. Soc. Am. 75, 749–768 (1984)]. Extending their initial condition to the case of a two‐frequency wave excitation, propagation curves and beam patterns of the difference frequency sound are obtained and compared with the measured data. All observations quantitatively agree very well with the numerical calculation. Nonlinear attenuation of spectral components by increasing the source pressure is clearly confirmed.

Higher order transverse mode suppression in surface acoustic wave resonators

Abstract: A technique for adjusting the frequency of odd mode transverse waves propagating in a SAW device is described. A pair of localized regions of frequency determining trimming material are deposited onto selected portions of a surface wave propagating surface, to provide localized regions on said surface where the odd order transverse mode has energy maxima. These regions change the acoustic properties and hence the velocity characteristics of the surface wave propagating surface in said regions. The frequency of the odd mode transverse wave is changed accordingly and is preferably changed to match that of the fundamental transverse propagating wave. This decreases the insertion loss of the device at the fundamental frequency and eliminates the odd mode transverse wave propagation characteristic within the operating frequency range of the resonator. In a preferred embodiment, the SAW device further includes an acoustically matched piezoelectric transparent cover disposed over the surface wave propagating surface having disposed thereon a trim pad which is selectively removed to provide the localized regions and thus the localized alterations in the acoustic properties of the surface acoustic wave device.

Duration and Frequency Characteristics of Tracheoesophageal Speech

Abstract: Selected characteristics were compared in the speech of five tracheoesophageal, five esophageal, and 15 normal laryngeal adult speakers. Tape-recorded speech samples were measured for durational features with a stopwatch. Frequency features were analyzed with a Visi-Pitch/Apple IIE computer interface with statistical subroutines. Tracheoesophageal speech proved comparable to normal speech in maximum phonation time, speech rate, pitch pertubation (jitter), average fundamental frequency, and fundamental frequency range, but less efficient than normal speech in phrase grouping. Tracheoesophageal speech was superior to esophageal speech in maximum phonation time, speech rate, and phrase grouping, but not significantly different in pitch perturbation, average fundamental frequency, and fundamental frequency range. Explanations and clinical implications of these findings are discussed.

A new voice-packet reconstruction technique

Abstract: The authors present a voice-packet reconstruction scheme in which the pitch and amplitude of a packet reconstructed according to the pitch detection method of D.J. Goodman et al. (1986) are modified to accommodate amplitude and slight fundamental frequency changes that might have been contained in the missing packet. Audible clicks in pitch-detection-reconstructed speech are therefore significantly reduced, and the perceived quality of reconstructed speech is improved. Preliminary subjective tests indicate that for a given perceptual quality (mean opinion score), the number of missing packets for this technique may be about twice what can be tolerated when using the pitch detection method only. >

Detecting single‐cycle frequency modulation imposed on sinusoidal, harmonic, and inharmonic carriers

Abstract: Thresholds for detecting frequency modulation (FM) of various carriers were measured in quiet and in noise. The carriers were either pure tones, harmonic complexes, or inharmonic complexes. The modulator was always a single cycle of a 12.5‐Hz sinusoid. When the carrier was a complex tone, each component of that carrier was modulated by the same percentage of its starting frequency. This is the form of FM that occurs when the fundamental frequency (F0) of a complex sound is modulated. Threshold was defined in terms of this percentage frequency change. Two phases of the modulator were used, producing percepts of either upward or downward frequency glides. Experiment 1 used sinusoidal carriers with frequencies between 200 and 2400 Hz. Thresholds were constant for carrier frequencies of 1200 Hz and above, increased below 800 Hz, and were higher for the ‘‘down’’ than for the ‘‘up’’ glides, especially with low carrier frequencies. Experiment 2 measured thresholds for carriers consisting of three adjacent harmon...

Wide-band fiber optic signal processor

Abstract: Operation of a 16-tap fiber-optic delay line configured as a bandpass filter with a fundamental frequency of 20 GHz over the frequency range from 0 to 125 GHz is discussed Equal tap weights and spacings were used to facilitate comparison of experimental and predicted results More than 10/sup 11/ analog multiplications per second are performed in this relatively simple signal processing system Other processors for performing functions such as matched filtering and correlation can be implemented by appropriate choice of the mirror reflectances and fiber lengths >

Analysis and simulation of small variations in the fundamental frequency of sustained vowels

Abstract: Analysis and simulation of small variations in the fundamental frequency of sustained vowels

Process and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid

Abstract: The invention relates to processes and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid. An electro-acoustic transducer according to the invention is a transducer of the double-tonpilz type, comprising two electro-acoustic drivers (1a, 1b) in line on both sides with a central counter-mass (2) and between two horns (3a, 3b). This mechanical assembly is located in a rigid box (4) which is fitted with side holes (5) and which delimits a cavity (7) housing elastic tubes (6) closed at their both ends and filled with gas so that the Helmholtz resonant frequency of the cavity (7) is close and preferably lower than the fundamental frequency of the axial vibrations of the vibrating assembly. An application of the invention is the construction of low-frequency transmitting transducers of the double-tonpilz type with a wide pass-band.

Automated method for determining total harmonic distortion

Abstract: The accuracy of an automated THD measurement performed by an FFT signal analyzer is improved by refining the estimate of the signal's fundamental frequency on which the THD analysis is based. This refinement is accomplished by calculating a parameter that represents the relative accuracy of the estimate and then varying the estimate to maximize the parameter. The result is a process which permits refinement of the fundamental frequency to an almost arbitrary accuracy, resulting in a highly improved measurement of THD.

A system for capturing and presenting short-duration voltage impulses on AC power lines

Abstract: Voltage impulses with frequency components substantially above the fundamental frequency can be found on AC power distribution systems. A system for capturing these impulses and presenting them for analysis is described. The system records both the impulse waveform and the fundamental waveform shape in digital FIFO (first in, first out) buffers. Both signals are continuously recorded; recording continues for an interval of time after triggering that is shorter than the depth of the FIFO buffers, yielding detailed pretrigger and posttrigger information. The results of some preliminary field investigations are discussed. They indicate that some terminology that has previously been used to describe impulse parameters, such as duration,' may no longer be useful. Initial analysis of impulse waveforms indicates that some impulse sources can be identified by their waveforms. >

Optical Mode Conversion In Magnetic Garnet Films

Abstract: Magnetic garnet films can be used as optical waveguides in the near infrared region. Light propagates in the waveguides as TE or TM modes. Due to the linear and circular magnetic birefringences these modes are coupled depending on the direction of the magnetization with respect to the direction of mode propagation. The efficiency of the mode conversion caused by the coupling is calculated. If the ferrimagnetic resonance is excited in the waveguide, a dynamical TE-TM mode conversion and thus a modulation of the light is induced. The spectrum of the modulated light contains besides the fundamental frequency higher harmonics. For a gallium-substituted film of yttrium iron garnet the dynamical mode conversion is measured for different orientations of the magnetization. A modulation efficiency of 6% at a frequency of 1 GHz is achieved. The experimental results are in qualitative agreement with calculations.

Harmonic frequency selecting circuit

Abstract: A harmonic frequency selecting circuit is provided that simply and effectively provides a desired harmonic frequency output signal and that eliminates the need for frequency multiplier circuits. The harmonic frequency selecting circuit includes an oscillator circuit for generating a fundamental frequency signal and a plurality of harmonic frequency signals of the fundamental frequency signal. A phase modulator circuit is coupled to the oscillator circuit for selectively variably attenuating the generated fundamental and harmonic frequency signals. A bandpass filter circuit is coupled to the phase modulator circuit for selecting a predetermined harmonic frequency output signal.

Generation of parallel second harmonic light rays using an optical fiber

Abstract: An arrangement for generating light at a second harmonic of an input light at a fundamental frequency/wavelength. Light at the fundamental frequency/wavelength is generated by a laser and impinges upon an input end of an optical fiber. The optical fiber has a non-linear optical characteristic and generates a second harmonic of the input light. The second harmonic which exits the fiber has an axisymmetrical and conical equiphase wave surface. A collimator lens collimates the second harmonic and parallel light rays are produced on the output side of the lens.

Effect of electrodes on the acceleration sensitivity of crystal resonators

Abstract: Based on Mindlin's first-order equations of plated crystal plates, a set of six coupled equations is derived in which the effect of the mass of the electrodes, the extensional elastic stiffness of the electrodes, and the thermal expansions of the plate and electrodes are taken into account. The principle of virtual displacements corresponding to these equations is obtained. Strains and displacement gradients in an electroded crystal disk subject to a steady acceleration are obtained from the finite-element solutions of the derived equations. By inserting these strains and displacement gradients in the frequency equation of the fundamental thickness vibrations of the disk and solving the frequency equation by a perturbation method, acceleration sensitivities of crystal resonators with various electrode arrangements are obtained. It is found that for small plate backs, say R >

Optimum Synthesis of Thin-Walled Vibrating Beams With Coupled Bending and Torsion

Abstract: This paper considers the optimum structural design of vibrating beams in which the inertial axes and the elastic axes are noncollinear. The condition of noncollinear axes exists in structures having unsymmetric cross-sections. For unsymmetric cross-sections the centroid and the shear center do not coincide. This results in coupling between some of the bending and torsional modes. This paper presents results for the simply supported and cantilever beams with a thin-walled channel cross-section. The minimization of the structural volume subject to multiple frequency constraints and its dual problem of maximization of the fundamental frequency subject to a volume constraint are considered. A quadratic extended interior penalty function with Newton’s method of unconstrained minimization is used in structural optimization. The structures considered have nonstructural masses besides their own mass.

Low-temperature measurement of the fundamental frequency response of a semiconductor laser by active-layer photomixing

Abstract: We use the active-layer photomixing technique to directly modulate the output of a GaAs semiconductor laser operating at temperatures as low as 4.2 K. The technique produces modulation with nearly perfect immunity to device parasitic effects, revealing the laser diode's intrinsic modulation response. At 4.2 K the parasitic corner frequency is estimated to be 410 MHz, yet the response appears ideal out to 15 GHz. We measure the dynamical parameters governing the response function, the relaxation resonance frequency, and the damping rate, and discuss their low-temperature behavior.