Showing papers on "Fundamental frequency published in 1974"

Transverse vibrations of double‐tapered cantilever beams with end support and with end mass

Abstract: The free vibrations of a double‐tapered cantilever beam with (1) end support and (2) end mass have been investigated using the Bernoulli‐Euler equation. The beam was tapered linearly in the horizontal and in the vertical planes simultaneously with the taper ratio in the horizontal plane equal to that in the vertical plane. A table is presented for the first case from which the fundamental frequency, second, third, fourth, and fifth harmonic can easily be obtained for various taper ratios. A chart, plotted from this table, shows the effect of taper ratio on the various harmonics. For the second case, a table and resulting charts show the effect of taper ratio and ratio of end mass to beam mass on the fundamental frequency and higher harmonies. Although previously presented, the case of the beam with free end is also included for purposes of comparison.

The optimum comb method of pitch period analysis of continuous digitized speech

Abstract: A new method of tracking the fundamental frequency of voiced speech is described. The method is shown to be of similar accuracy as the Cepstrum technique. Since the method involves only additions, no multiplication, it is shown to be faster than the SIFT algorithm. The basis of the method is searching for a minimum in the magnitude of the difference between a speech segment and a delayed speech segment. This is shown to be equivalent to selecting the comb filter which best annihilates the input signal.

Device for synthesizing frequencies which are rational multiples of a fundamental frequency

Abstract: A frequency synthesizer is disclosed which can provide frequencies which are rational multiples of a fundamental reference frequency. The synthesizer includes a voltagecontrolled oscillator in a phase-locked loop with the reference frequency. A modulo-N counter is included to allow synthesis of harmonics of the reference frequency. To obtain rational fractional frequencies between harmonics a ''''cycle swallower'''' is provided to occasionally abruptly shift the phase of the oscillator output. The swallowing rate is determined by the contents of a storage register which is pre-loaded with a representation of the desired frequency. The contents of this storage register are periodically loaded into and accumulated in an accumulator which generates an overflow signal to the cycle swallower whenever the accumulated value exceeds its maximum storage capacity. In response to the average rate of phase shifting by the swallower, the loop stabilizes when the oscillator frequency is equal to the desired rational multiple of the reference frequency.

Harmonic ratios of inverted-U type III bursts

Abstract: The harmonic ratios of a large sample of inverted-U bursts are found to be smaller at the turning frequency than at the starting frequency. Ratios <2.0 are explained by postulating that the lowest fundamental frequencies emitted are prevented from escaping from the corona by an evanescent region between the source and the observer. This concept is used to construct a source model for inverted-U bursts where the density is lower inside a magnetic flux tube than it is outside.

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.

Harmonic modulation and loudness scaling in a computer organ

Abstract: Harmonic modulation and loudness scaling are implemented in a computor organ of the type wherein successive sample point amplitudes of a musical waveshape are computed in real time and converted to musical tones. Each sample point amplitude is obtained by summing a set of separately evaluated constituent Fourier components. The amplitude envelope of the generated tone is established by a set of scale factors S(t) that vary in value during attack and decay. Harmonic modulation is achieved by including in each sample point amplitude summation only those constituent Fourier components having an order lower than a maximum value that is fractionally proportional to the envelope amplitude scale factor S(t). Loudness scaling is achieved by effectively multiplying each obtained sample point amplitude by a loudness scale factor related to the fundamental frequency of the generated tone. These scale factors are selected so that notes of lower frequency are augmented in loudness to compensate for decreased hearing response at low frequencies.

Phase‐matched guided optical second harmonic wave generation in oriented ZnS polycrystalline thin‐film waveguides

Abstract: The first experimental verification of phase‐matched SHG was performed in the polycrystalline ZnS thin‐film waveguide deposited on a BK‐7 glass substrate. The complete phase‐matching between the TE1 mode at the fundamental frequency of 1.054 μm and the TM4 mode at its second harmonic wave was realized by using a tunable optical parametric oscillator. The interaction length estimated from the tuning curve for the phase matching was about 35 μm and the output harmonic power was of the order of milliwatts at 300‐W fundamental input under the phase‐matched condition.

Poling Dependence of the Surface-Wave Frequency-Generation on PZT

Abstract: The influence of poling on the frequency of surface acoustic waves was experimentally studied using PZT and several interdigital transducers with the same period but different finger width and spacing. The poling was done by applying a dc electric voltage across the transducer electrodes near the Curie temperature, Tc. With weak poling, transducer fingers wider than or equal to the spacing generated second- and fourth-harmonic signals (referred to the fundamental frequency normally expected of the transducer). The generated second-harmonic increased to a saturation value while the fourth, first increased, and then decreased as poling was carried to completion. For transducers with fingers narrower than the spacing, the generation of the fourth harmonic was too weak to observe. The largest conversion efficiency, -8.5 dB, was obtained for second harmonic generation using transducer fingers slightly wider than the spacing. This efficiency was comparable with that of the same transducer on a uniformly poled PZT generating the fundamental frequency. These results indicate that second- and fourth-harmonic generation for appropriate poling conditions and transducer geometry is possible and extension of the transducer-frequency capability without size reduction can be achieved.

A simplified representation of the vertical plane dynamics of ses craft

Abstract: The basic dynamics of sidewall-type surface effect ships for vertical plane motions (heave and pitch) in response to waves is established in terms of the fundamental frequency characteristics and other critical parameters that affect craft motion. The effects of leakage variations and seal action in producing pressure variations, vehicle accelerations, and motions, etc., are illustrated by time histories of motion variables via computer simulation. The vehicle's basic dynamic characteristics provide insight into the different aspects of control that may be applied to achieve improved motion and habitability performance. A discussion of the problems associated with scaling model test results, together with techniques for the proper prediction of full-scale dynamic performance, also is provided.

Quartz crystal vibrator with partial electrodes for harmonic suppression

Abstract: It is disclosed a quartz crystal vibrator for a timepiece having a partial electrode which is able to offset the charge produced by higher harmonic oscillation. According to this invention, higher harmonic oscillation is prevented and vibrators oscillate by only fundamental frequency.

Solid state microwave cavity oscillator operating below cavity cutoff frequency

Abstract: A microwave oscillator using a Gunn diode in a section of rectangular waveguide tuned to resonate as a cavity to a fundamental frequency that is below the waveguide cutoff frequency has its output for the fundamental frequency located at a place in the cavity at which a peak of the fundamental frequency wave and a null of the second harmonic coincide. Fundamental frequency output is taken in a direction transverse to the axis of the waveguide. Harmonic frequency energy can also be taken from the waveguide section, or suppressed, as desired.

Transient response of a thin-wire antenna or scatterer near a conducting ground plane

Abstract: Using frequency domain integral equation solutions for the current flowing on a thin-wire antenna or scatterer located over a perfectly conducting ground plane, the time domain response of the current is determined by Fourier inversion. Typical results are presented along with summary curves depicting the shift in fundamental frequency of oscillation and the change in damping constants for the fundamental mode as the wire position is varied.

An algorithm for modeling the sinusoidal input/steady-state response behavior of nonlinear systems over a set of frequencies and amplitudes☆

Abstract: An algorithm for constructing a black box model of the sinusoidal input/steady-state response behavior of nonlinear time-invariant systems over a set of frequencies and amplitudes is presented. It is assumed that the steady-state response is periodic of the same fundamental frequency as the excitation, and that the Fourier coefficients are continuous functions of amplitude and square-integrable functions of frequency. The algorithm converges, in a mean-square sense, to an exact representation of the first N harmonics of the steady-state response minus its d.c. component. The model constructed by the algorithm admits a relatively simple physical realization characterized by 2NM+1 linear dynamic elements, and N(2M+1)+1 nonlinear static elements. The underlying mathematical structure of the model is an orthogonal series expansion relative to time whose coefficients are themselves truncated orthogonal expansions relative to frequency. Here M, the number of harmonics used for frequency interpolation, is determined by the algorithm. Of the N(2M+1)+1 memoryless nonlinearities which characterize the model, N of these are specified ahead of time (Tchebysheff polynomials), and 2NM+1 are parameters which mold the representation to the specific system being modeled. Each of these functions of a single variable can be obtained in a pointwise manner directly from steady-state measurements. The algorithm was implemented on a digital computer, and forced versions of the classic equations of van der Pol and Duffing were run as examples. An additional analytic example of a frequency multiplier of prescribed bandwidth was also presented.

Automatic formant tracking

Abstract: A formant tracker has been implemented which assigns frequency, amplitude, and bandwidth to each of the first three formants for each 10‐msec voiced segment of continuous speech. Its input parameters are fundamental frequency, rms, and up to five spectral peaks below 5000 Hz with their respective amplitudes and bandwidths. Peak information is obtained from linear prediction spectra. Techniques distinguishing this formant tracker from previously reported ones are as follows: (1) All spectrum computations are accomplished in the peak picking phase, before ferment tracking—this may yield spurious formants but few missing ferments. (2) Anchor points are located by selecting three consecutive 10‐msec segments in which three formant frequencies do not differ from one segment to the next by more than a threshold amount. Tracks for the first three ferments are extended in both directions from these anchor points. (3) Frequency pattern matching aids decision making when more than one ferment is possible for a given slot; this is particularly useful for nasals and /l/ and /w/. Frequency pattern information is derived from speaker vowel‐sonorant frequency tables. [This research was supported by the Advanced Research Projects Agency of the Department of Defense under Contract No. DAHC15‐73‐C‐0080.]

BIAX analog storage element

Abstract: The behavior of the BIAX device as an analog storage element is presented. BIAX, which is used primarily as a digital computer memory device, is applied as an analog storage element by using discrete levels of the flux range available around the storage hole. It is predicted from simple theory assuming equivalent uniaxial anisotropy that the stored flux levels can be read nondestructively by detecting the fundamental frequency component of induced voltage under the application of a dc bias and a sinusoidal readout magnetic field, and that the voltage is proportional to the flux levels and read-out magnetic fields. These characteristics are experimentally verified. The accuracies of readout with respect to the input-voltage-time integral and the stored flux levels are 14.6% and 2.1%, respectively. The drive frequency is in the range of 1 to 1000 kHz. The static and dynamic characteristics are improved with the ac bias field of high frequency. The element has the advantages of more than one bit per core site, large output levels, and high signal-to-noise ratio.

Binary control data transmission circuit - transmission between F.M VHF broadcast senders with stereo transmission

Abstract: A V.H.F. stereo transmission system employs main senders and filling senders operated through relay receivers. Data is transmitted by frequency keyed carrier signals inserted into the transmission frequency band. The carrier signal frequencies are near the stereo pilots, and are derived from a fixed frequency generator by a frequency divider whose division ratio can be changed by the binary control data. They are at the receiving end filtered out by n-path filters controlled by a generator of the same fundamental frequency through two frequency dividers with the same division ratio, and demodulated by shift-registers controlled by the same fundamental frequency. Each of the several control channels has an individual generator with individual fundamental frequency and frequency divider, and individual filtering and demodulation means at the receiver.

Theory of second harmonic generation in focused light beam of fundamental frequency with the Gaussian distribution of light intensity under the interaction of type o+o→e

Abstract: A process of generation of second harmonic frequency (S.H.G.) in focused light beam with the Gaussian distribution of light intensity is studied with the help of generalized diffraction theory in this work. Three methods of focusing are considered, namely, focusing with the spherical lens, focusing with the cylindrical lens in the plane of the principal cut and finally focusing with the cylindrical lens in the plane perpendicular to the plane of the principal cut. Two cases are discussed, namely, the case of S.H.G. in “diffractionless” light beam and the case of S.H.G. in strongly diffracted light beam.

Broad band high efficiency amplifier with improved band width

Abstract: An active high-efficiency-mode semiconductor diode is coupled to oscillating high frequency fields in a transmission line network for amplifying those electromagnetic fields, the apparatus taking the form of a single port high frequency device. The selected diode and the transmission line network provide means for elimination of time delayed triggering of undesired oscillations within the amplifier. Further, operating band width is increased by selection of a diode package that is anti-resonant at the second harmonic of the fundamental frequency signal being amplified, the diode itself reflecting small-signal negative resistance characteristics at that harmonic.

Fast neutron damage in superconducting vanadium

Abstract: A single crystal of vanadium (resistivity ratio Γ = 450) was irradiated in the Oak Ridge Research Reactor at a temperature of 40°C for a series of fast neutron fluences The sample was a prolate spheroid approximately 25 mm in length, with a minor diameter of about 3 mm Prior to and after each irradiation isothermal bulk magneti­zation measurements were carried out at various temperatures in the superconducting regime The sample was also investigated in a Hartshorn mutual inductance bridge before and after each irradiation The bridge apparatus1 was arranged so that the sample could be excited by a sinusoidal magnetic field of adjustable frequency ω and amplitude h0 in a superposed dc biasing field H Both fields were parallel to the long axis of the sample The bridge was balanced with the sample in the Meissner state, so that the output was proportional to the ac magnetic permeability and could be viewed on an oscilloscope A lock-in amplifier at the bridge output tuned to the fundamental frequency detected signals in quadrature proportional to μ’ and μ”, the real and imaginary components of the fundamental portion of the ac permeability, which is generally nonlinear

The Optimum Comb Method of Pitch Period Analysis of Continuous Digitized Speech

Abstract: A new method of tracking the fundamental frequency of voiced speech is described. The method is shown to be of similar accuracy as the Cepstrum technique. Since the method involves only additions, no multiplication, it is shown to be faster than the SIFT algorithm. The basis of the method is searching for a minimum in the magnitude of the difference between a speech segment and a delayed speech segment. This is shown to be equivalent to selecting the comb filter which best annihilates the input signal.

Harmonics and the fundamental-frequency negative conductance of Gunn diodes

Abstract: Parametric interactions of X-band Gunn diodes between the frequencies 10 and 20 GHz are studies with the help of a coaxial resonator. A diode is placed at various positions along the central conductor so that different load impedances are applied. Very strong variations in microwave amplitude behaviour of the two frequencies were observed, which indicate pronounced interactive effects. These are studied by measuring the negative-conductance as a function of r.f. diode voltage. So far, only a decrease in fundamental-frequency conductance function has been observed due to the presence of harmonic power.