Showing papers on "Fundamental frequency published in 1988"

Analytical analysis of the harmonic effects of a PWM AC drive

Abstract: A novel analysis is presented of the harmonic content of current, torque pulsations, and harmonic copper losses of a three-phase induction machine fed by a two-phase pulsewidth modulation (PWM) inverter. The purely analytical results are based on the assumption that the switching frequency is high compared with the fundamental frequency. It is shown that the results hold accurately for frequency ratios f/sub s//f/sub 1/>9. >

Spectral analysis interpretation of electro-surgical generator nerve and muscle stimulation

Abstract: The frequency spectra of two commercial electrosurgical generators were examined during stimulated tissue cutting and compared to radio-frequency animal nerve and muscle stimulation curves generated from high-frequency sinusoidal current. During electrosurgical cutting, significant energy can exist at the fundamental frequency, as well as at frequencies lower and greater than the fundamental, which may be stimulatory to both nerve and muscle tissue. Different types of biological loads did not seem to significantly affect the spectra of each individual electrosurgical unit (ESU). However, the interaction of a specific ESU output with the biological load when compared to a pure resistive load accounts for varying impedances and resultant modulations of the fundamental frequency. Reducing electrosurgical side effects and hazards may depend, in part, on a better understanding of these underlying mechanisms. >

Measuring the rate of change of voice fundamental frequency in fluent speech during mental depression

Abstract: A method of measuring the rate of change of fundamental frequency has been developed in an effort to find acoustic voice parameters that could be useful in psychiatric research. A minicomputer program was used to extract seven parameters from the fundamental frequency contour of tape‐recorded speech samples: (1) the average rate of change of the fundamental frequency and (2) its standard deviation, (3) the absolute rate of fundamental frequency change, (4) the total reading time, (5) the percent pause time of the total reading time, (6) the mean, and (7) the standard deviation of the fundamental frequency distribution. The method is demonstrated on (a) a material consisting of synthetic speech and (b) voice recordings of depressed patients who were examined during depression and after improvement.

High impedance fault analyzer in electric power distribution

Abstract: A system (Fig. 3) and method for detecting an abnormality in a network (10) for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal (40) representing the fundamental frequency and another signal (42) representing a harmonic current occuring in the network. The phasor relation between the fundamental voltage and harmonic current representing signal are compared (44). The system produces a signal (82) indicating the occurence of a high impedance fault in response to a predetermined change in the compared phasor relationship. Embodiments (Figs. 5 and 6) are disclosed utilizing expression of signals within the network in polar coordinates, as well as embodiments (Fig. 11) utilizing signals expressed in rectangular coordinates. Such embodiments include both circuitry for detecting zero crossing phenomena, as well as circuitry for producing representation of signal phasor products.

Perception of the missing fundamental in nonhuman primates.

Abstract: In preparation for neurophysiological experiments aimed at mechanisms of pitch perception, four rhesus monkeys were trained to press a button when the fundamental frequencies (missing or present) of two complex tones in a tone pair matched. Both tones were based on a five‐component harmonic series. Zero to three of the lowest components could be missing in the first tone, while the second (comparison) tone contained all five harmonics. The range of fundamentals tested varied from 200 to 600 Hz. Three monkeys learned to match tones missing their fundamentals to comparison harmonic complexes with the same pitch, whereas the fourth monkey required the physical presence of the fundamental. Consideration of several cues available to the monkeys suggests that the animals could perceive the missing fundamental.

A pitch‐synchronous analysis of hoarseness in running speech

Abstract: A method of pitch‐synchronous acoustic analysis of hoarseness requiring a voice sample of only four fundamental periods is presented. This method calculates a noise‐to‐signal (N/S) ratio, which indicates the depth of valleys between harmonic peaks in the power spectrum. The spectrum is calculated pitch synchronously from a Fourier transform of the signal, windowed through a continuously variable Hanning window spanning exactly four fundamental periods. A two‐stage procedure is used to determine the exact duration of the four fundamental periods. An initial estimate is obtained using autocorrelation in the time domain. A more precise estimate is obtained in the frequency domain by minimizing the errors between the preliminary calculated power spectrum and the predicted spectrum spread of a windowed harmonic signal. Analysis of synthesized voices showed that the N/S ratio is sensitive to additive noise, jitter, and shimmer, and is insensitive to slow (8 Hz) modulation in fundamental frequency and amplitude. An analysis of pre‐ and postoperative voices of six patients with benign laryngeal disease showed that the N/S ratio for vowel /u/ in running speech consistently improved after surgery for all subjects, in agreement with their successful therapeutic results.

High impedance fault analyzer in electric power distribution networks

Abstract: A system and method is disclosed for detecting an abnormality in a network for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal representing the fundamental frequency and another signal representing a harmonic current occurring in the network. The phasor relation between the fundamental voltage and harmonic current representing signal are compared. The system produces a signal indicating the occurrence of a high impedance fault in response to a predetermined change in the compared phasor relationship. Embodiments are disclosed utilizing expression of signals within the network in polar coordinates, as well as embodiments utilizing signals expressed in rectangular coordinates. Such embodiments include circuitry for detecting zero crossing phenomena, as well as circuitry for producing representation of signal products.

The effect of optical feedback on the relaxation oscillation in semiconductor lasers

Abstract: The influence of weak optical feedback on the relaxation oscillation in semiconductor lasers is studied both theoretically and experimentally. In the approximation used the frequency branches of the relaxation oscillation are described by multiples of the fundamental frequency of the external cavity. However, especially for the low multiples, the deviation from this behavior is quite pronounced. The authors discuss the dependence of the frequency and the damping rate on the length of the external cavity in detail. Furthermore, they find that the damping rates that correspond to the various frequency branches are quite different. The accessibility of the various frequency branches is determined by the damping rates that belong to them. >

Parasitic-free measurement of the fundamental frequency response of a semiconductor laser by active-layer photomixing

Abstract: We report the measurement of the fundamental (intrinsic) frequency response of a GaAs semiconductor laser to 12 GHz by directly photomixing two optical sources in the active region of the laser. This novel technique reveals the underlying fundamental frequency response of the device as parasitic effects are avoided. Well beyond the relaxation resonance, the theoretically predicted 40 dB/dec signal rolloff is observed. Other features of the measured response function are also observed to be the theoretical ideal.

Mechanisms for the interaction between nonstationary electric fields and biological systems II. Nonlinear dielectric theory and free-energy transduction

Abstract: A discussion of nonlinear dielectric phenomena and their relationship to freeenergy transduction in biological systems is given. It transpires that the conditions required for observing the nonlinear dielectric behavior of biological membranes can be expected under easily realizable circumstances, and may potentially form the basis for powerful techniques for studying membrane and other proteins in their native environment. We develop a nonlinear dielectric theory, which generalizes the dielectric permittivity to include real and imaginary parts of harmonics of the fundamental frequency. An analytical relationship is derived between these permittivities and the kinetic constants of a model protein. Of special relevance is the occurrence of higher harmonics in the dielectric displacement even when the exciting electric field consists of a single sinusoidal frequency. This is manifested by the analytical result that the corresponding higher order permittivities are in general not equal to zero, as ...

Method for determining absolute current density through an implanted electrode

Abstract: A method for determining absolute current density through an implanted electrode measures the fundamental and harmonic components of an electrical current passing through the electrode and estimates the absolute current density from the ratio between the magnitude of the electrical current measured at one of the harmonics on the fundamental frequency. Another method of the invention applies a wideband noise input voltage to the electrode under investigation and measures the spectrum of the input voltage and output current to determine a first transfer function. A second transfer function representing an increase magnitude of wideband noise input voltage is also obtained. A difference transfer function is computed and used to determine absolute current density through the electrode. The methods may be practiced non-invasively.

Dual-mode resonant scanning system

Abstract: A dual-mode resonant scanning system comprising an electronic control circuit and a dual-mode resonant mechanical scanner to produce an essentially triangular scan pattern. The dual-mode mechanical scanner is mechanically tuned to simultaneously oscillate at a predetermined fundamental frequency and a free running third harmonic thereof. The electronic control circuit drives the mechanical scanner to oscillate at the exact third harmonic of the predetermined fundamental frequency and phase locks the harmonic oscillation to the fundamental oscillation. The dual-mode resonant mechanical scanner includes an optical scanning element having a first mass, a second mass, at least one torsion rod, a rotational actuator and a mechanical ground designed and integrated together such that the mechanical scanner is self resonant at the predetermined fundamental frequency and at or within a few hertz of the exact third harmonic of the predetermined fundamental frequency. The electronic control circuit includes a mirror-position sensing subsystem, a bandpass filter tuned to the predetermined fundamental frequency, a multiplier circuit, a summing circuit, a manual phase and amplitude adjustment, a scan angle automatic gain control circuit and a driving circuit. The exact third harmonic oscillation in combination with the fundamental oscillation produces an essentially constant scan rate through a predetermined scan angle.

Electronic musical instrument

Abstract: PURPOSE:To shorten a time delay extending from picking a string to sounding by storing pitch information corresponding to a fundamental frequency and pitch information of the string, etc., corresponding thereto, changing the pitch information of the string, etc., at the time of acting by said both pitch information and determining a musical sound pitch. CONSTITUTION:By a guitar synthesizer, a changeover switch 6 is set to a storage mode, each fret is made open and a string is picked. This vibration is detected as a pitch A by a pitch detector 4, and stored in a memory 8. When the switch 6 is switched to a musical performance mode, and a performer picks the string in a state that the fret has been held down, its pitch (p) is detected by the pitch detector 4, and supplied to an arithmetic means 10. The means 10 calculates a pitch of a musical sound to be sounded by P'=P.B/A, based on a pitch P, a storage pitch A of the memory 8 and a pitch B of a reference pitch memory 12, and a sound source 14 supplies it in order to generate a musical sound, based thereon. In such a way, a time delay extending from picking the string to sounding can be prevented by the sound source 14.

Resonance‐frequency discrimination

Abstract: Measurements of the just‐noticeable change in resonance frequency ∼(ΔF)r of a second‐order filter are reported. The source signal was either periodic, with or without a smooth change in fundamental frequency, or it was random white noise. These differences in the nature of the source had little effect on ∼(ΔF)r. Over the investigated ranges of reference resonance frequency (Fr=300 to 2000 Hz) and filter selectivity (Q=1 to 36), the results are well summarized by ∼(ΔF)r=0.079 Fr/(Q)1/2. The data were used to evaluate filter‐bank models employing different filter shapes and performance‐prediction schemes. A good fit to the resonance‐discrimination data was obtained with filters derived in a masking study by Patterson [J. Acoust. Soc. Am. 55, 802–809 (1974)] and with performance based on use of the maximum level difference over all bands. The latter finding indicates that listeners may not make optimal use of small level differences distributed over multiple bands.

On the measurement of glottal flow.

Abstract: For developing a comprehensive description of voiced speech sounds in terms of a phonation and an articulation component, it is necessary to know to what extent the volume flow modulations at the entrance of the vocal tract are due to vocal fold motions and to what extent they are due to variations in the transglottal pressure. In order to be able to study this problem, it is important that the flow at the glottis can be measured during normal speech production in a reliable fashion. In this article, a flow measurement technique is described that differs from the more usual inverse filtering approach to the extent that the flow is not measured at the mouth, but much closer to the glottis. The technique is based on the measurement of pressure gradient. It is shown that the proposed method also leads to an inverse filtering problem, but that, since this problem is much simpler, the gradient method yields more reliable estimates of the shape of the glottal flow waveform, though without the zero flow level (dc component) and without a magnitude scale. By means of theoretical considerations about velocity profiles in pulsatile flow in cylindrical tubes, it is shown that the method for measuring flow during phonation proposed in this article may be expected to yield reasonable flow waveform estimates in a frequency region from any normal fundamental frequency to an upper frequency determined by the transducer sensitivity and separation and vocal tract geometry. In this case, the frequency limitation was estimated to be 1000 Hz. The merits of the newly developed method are evaluated by means of a modeling study and by carrying out some cross‐checks on real measurement data.

A distributed broadband monolithic frequency multiplier

Abstract: A broadband frequency doubler that uses distributed amplifier techniques has been designed to operate over several octaves of bandwidth. The circuit design suppresses the fundamental frequency energy present at the output port while maximizing the second harmonic signal. The design can be realized using monolithic or conventional microwave circuit techniques for use in local oscillator chains. To demonstrate the multiplier concept, a two-cell monolithic circuit was designed. The doubler is composed of four FETs with gate widths of 176 mu m. The completed frequency doubler chip was used in the design of a 5-9-GHz (10-8-GHz output frequency) multiplier chain. The chain used several stages of post- and preamplification to set input drive levels and to provide increased local oscillator power. A 9-dB variation in input power produces only 3 dB of output power variation. With the chain fully driven, the total power output variation is less than +or-1 dB. The multipliers exhibit excellent power output characteristics, with fundamental frequency suppression, and require no tuning. >

A wearable multichannel tactile display of voice fundamental frequency.

Abstract: This paper describes a wearable sensory aid that provides the deaf with tactually encoded information about intonation. Fundamental frequency is represented as both place and rate of vibration in a linear array of solenoids. Pitch extraction is accomplished through low-pass filtering and peak detection. A microcomputer is used to measure pitch period, which in turn determines which of the solenoids is actuated. By comparing consecutive periods, the system discriminates against random, noise-related inputs. The device is switchable between 1-, 8-, and 16-channel operation. The electronics package is contained in a case that may be worn on a belt. The solenoid array is worn on the forearm. The system is powered by five, rechargeable lithium cells and runs for at least 6 hours between charges. Proposed developments include the incorporation of digital pitch extraction methods and the option to use the spatial output dimension to encode speech parameters other than fundamental frequency.

Wiggler taper optimization for free electron laser amplifiers with moderate space-charge effects

Abstract: The standard synchronous tapering method used to design the wiggler magnetic field for free electron laser (FEL) amplifiers operating in the Compton regime will not work for amplifier systems where space-charge effects are important. The space-charge effects lower the overall gain in the amplifier system and, even more importantly, shift the peak in the gain curve to magnetic field values that are significantly less than the synchronous magnetic field value. As a result, the overall predicted gain using the synchronous tapering method is too low. Moreover, the synchronous magnetic field corresponds to the peak in the gain curve for a frequency below the fundamental frequency. Consequently, shot noise at frequencies below the fundamental frequency can grow to levels that may prevent amplification of the fundamental. We have developed a new tapering strategy that improves the predicted amplifier gain and circumvents the shot-noise growth for systems with moderate space-charge effects. For this new strategy, we hold the wiggler magnetic field constant at a value below the synchronous value but near the peak of the gain curve for the fundamental frequency, for some optimized length at the front end of the wiggler. Beyond this constant wiggler section, the field is tapered using the standard synchronous tapering algorithm. This new tapering scheme results in significant improvement in predicted amplifier gains and limits the growth of shot noise to insignificant levels. We demonstrate the effectiveness of this new tapering algorithm using the tapered wiggler design for the proposed microwave heating experiment (MTX) at the Lawrence Livermore National Laboratory (LLNL).

An approach to co-channel talker interference suppression using a sinusoidal model for speech

Abstract: The technique fits a sinusoidal model to additive vocalic speech segments such that the least mean square error between the model and the summed waveforms is obtained. Enhancement is achieved by synthesizing a waveform from the sine waves attributed to the desired speaker. Least squares estimation is applied to obtain sine-wave amplitudes and phases for both talkers, based on either a priori sine-wave frequencies or a priori fundamental frequency contours. When the frequencies of the two waveforms are closely spaced, the performance is significantly improved by exploiting the time evolution of the sinusoidal parameters across multiple analysis frames. The least squares error approach is also extended to estimate fundamental frequency contours of both speakers from the summed waveform. The results obtained, though limited in their scope, provide evidence that the sinusoidal analysis/synthesis model with effective parameter estimation techniques offers a promising approach to the problem of cochannel talker interference suppression over a range of conditions. >

Changes in Vocal Fundamental Frequency at the Segmental Level

Abstract: in addition to cycle-by-cycle (jitter) and long-term (intonation contour and declination) changes, vocal fundamental frequency (F0) is known to vary during moments of production of individual phone...

Digital audio signal processor

Abstract: A digital signal processing apparatus is provided for identifying the octave, note and cent of a musical sound. The apparatus includes a transducer for converting the musical sound into an electrical signal, a digital detection unit, receiving the electrical signal from the transducer, for determining the octave, note and cent of the material sound by detecting a fundamental frequency of the electrical signal; and a display unit, responsive to the detection unit, for displaying the note as an alphanumeric character and the cent as a positive or negative decimal integral number from -49 to +50 with zero cents representing perfect concert pitch.

Second harmonic generation with 5-chloro-2-nitroaniline

Abstract: Devices for and method of generating coherent second harmonic light radiation The devices comprise a laser source of coherent light radiation at a fixed fundamental frequency, crystalline 5-chloro-2-nitroaniline that crystallizes in a non-centrosymmetric configuration, means for directing the output radiation of the laser onto the 5-chloro-2-nitroanilane, and output means for utilizing the second harmonic frequency