Showing papers on "Fundamental frequency published in 1996"

Neural correlates of the pitch of complex tones. II. Pitch shift, pitch ambiguity, phase invariance, pitch circularity, rate pitch, and the dominance region for pitch.

Abstract: 1. The neural correlates of low pitches produced by complex tones were studied by analyzing temporal discharge patterns of auditory nerve fibers in Dial-anesthetized cats. In the previous paper it was observed that, for harmonic stimuli, the most frequent interspike interval present in the population of auditory nerve fibers always corresponded to the perceived pitch (predominant interval hypothesis). The fraction of these most frequent intervals relative to the total number of intervals qualitatively corresponded to strength (salience) of the low pitches that are heard. 2. This paper addresses the neural correlates of stimuli that produce more complex patterns of pitch judgments, such as shifts in pitch and multiple pitches. Correlates of pitch shift and pitch ambiguity were investigated with the use of harmonic and inharmonic amplitude-modulated (AM) tones varying either in carrier frequency or modulation frequency. Pitches estimated from the pooled interval distributions showed shifts corresponding to "the first effect of pitch shift" (de Boer's rule) that is observed psychophysically. Pooled interval distributions in response to inharmonic stimulus segments showed multiple maxima corresponding to the multiple pitches heard by human listeners (pitch ambiguity). 3. AM and quasi-frequency-modulated tones with low carrier frequencies produce very similar patterns of pitch judgments, despite great differences in their phase spectra and waveform envelopes. Pitches estimated from pooled interval distributions were remarkably similar for the two kinds of stimuli, consistent with the psychophysically observed phase invariance of pitches produced by sets of low-frequency components. 4. Trains of clicks having uniform and alternating polarities were used to investigate the relation between pitches associated with periodicity and those associated with click rate. For unipolar click trains, where periodicity and rate coincide, physiologically estimated pitches closely follow the fundamental period. This corresponds to the pitch at the fundamental frequency (F0) that is heard. For alternating click trains, where rate and periodicity do not coincide, physiologically estimated pitches always closely followed the fundamental period. Although these pitch estimates corresponded to periodicity pitches that are heard for F0s > 150 Hz, they did not correspond to the rate pitches that are heard for F0s 150 Hz. Pitches for high-pass-filtered alternating click trains were estimated from pooled responses of fibers with characteristic frequencies (CFs) > 2 kHz. Roughly equal numbers of intervals at 1/rate and 1/F0 were found for all F0s studied, from 80 to 160 Hz, producing pitch estimates consistent with the rate pitches that are heard after high-pass filtering. The existence region for rate pitch also coincided with the presence of clear periodicities related to the click rate in pooled peristimulus time histograms. These periodicities were strongest for ensembles of fibers with CFs > 2 kHz, where there is widespread synchrony of discharges across many fibers. 6. The "dominance region for pitch" was studied with the use of two harmonic complexes consisting of harmonics 3-5 of one F0 and harmonics 6-12 of another fundamental 20% higher in frequency. When the complexes were presented individually, pitch estimates were always close to the fundamental of the complex. When the complexes were presented concurrently, pitch estimates always followed the fundamental of harmonics 3-5 for F0s of 150-480 Hz. For F0s of 125-150 Hz, pitch estimates followed one or the other fundamental, and for F0s < 125 Hz, pitch estimates followed the fundamental of harmonics 6-12. (ABSTRACT TRUNCATED)

Unsteadiness and convective instabilities in two-dimensional flow over a backward-facing step

Abstract: A systematic study of the stability of the two-dimensional flow over a backward-facing step with a nominal expansion ratio of 2 is presented up to Reynolds number Re = 2500 using direct numerical simulation as well as local and global stability analysis. Three different spectral element computer codes are used for the simulations. The stability analysis is performed both locally (at a number of streamwise locations) and globally (on the entire field) by computing the leading eigenvalues of a base flow state. The distinction is made between convectively and absolutely unstable mean flow. In two dimensions, it is shown that all the asymptotic flow states up to Re = 2500 are time-independent in the absence of any external excitation, whereas the flow is convectively unstable, in a large portion of the flow domain, for Reynolds numbers in the range 700 [les ] Re [les ] 2500. Consequently, upstream generated small disturbances propagate downstream at exponentially amplified amplitude with a space-dependent speed. For small excitation disturbances, the amplitude of the resulting waveform is proportional to the disturbance amplitude. However, selective sustained external excitation (even at small amplitudes) can alter the behaviour of the system and lead to time-dependent flow. Two different types of excitation are imposed at the inflow: (i) monochromatic waves with frequency chosen to be either close to or very far from the shear layer frequency; and (ii) random noise. It is found that for small-amplitude monochromatic excitation the flow acquires a time-periodic behaviour if perturbed close to the shear layer frequency, whereas the flow remains unaffected for high values of the excitation frequency. On the other hand, for the random noise as input, an unsteady behaviour is obtained with a fundamental frequency close to the shear layer frequency.

Control of square-wave inverters in high power hybrid active filter systems

Abstract: This paper presents a new control scheme for a hybrid parallel active filter (HPAF) system intended for high-power applications-up to 100 MW nonlinear loads-to meet IEEE 519 recommended harmonic standards. The active filter inverter is realized with small-rated (1%-2% of the load rating) square-wave inverters operating at the dominant harmonic frequencies. The proposed system achieves harmonic isolation at desired dominant harmonic frequencies, such as the fifth and seventh, even in the presence of supply voltage harmonic distortions. A novel method of active filter inverter DC-bus control, as proposed here, achieves power balancing by exchanging energy at the fundamental frequency and at the dominant harmonic frequency (such as the fifth). The proposed square-wave inverter-based HPAF system provides improved filtering characteristics as compared to the conventional passive filter and is expected to be cost effective for high-power nonlinear loads compared to the conventional passive filter or other active filtering solutions. The concept of harmonic isolation at dominant harmonic frequencies by square-wave inverters with the proposed control scheme is validated by simulation results.

Adaptive suppression of vibrations - a repetitive control approach

Abstract: The aim of this paper is to present an adaptive solution to suppression of vibrations. Adaptation is appropriate whenever the fundamental frequency is unknown or drifting, e.g., when the vibration is caused by a rotational machine with unknown rotational speed. The approach presented here has its roots in repetitive control based on models of isolated frequencies rather than the commonly used delay model. The relationship between different modeled frequencies is fixed by the model structure, and the fundamental frequency is obtained by gradient descent or Newton's method. To show the feasibility of this approach, it was used to reduce the vibrations on a lever that were caused by a motor with imbalance in its rotation. As an actuator, a standard loudspeaker was used, and the vibration was sensed by an accelerometer.

Experimental study of self-sustained oscillations in a confined jet.

Abstract: We present an experimental study of a planar jet confined in a rectangular cavity. In certain geometrical configurations and for sufficiently large Reynolds numbers, this system exhibits self-sustained oscillations characterized by a well-defined wavelength and frequency of the jet. We describe flow regimes observed by varying the Reynolds number and the cavity length. The self-sustained oscillation regime is studied in detail: we extract the fundamental frequency and determine the selection criterion for the wavelength using a method of visualization, which has the advantage of being non intrusive. We show the existence of a band of allowed wavelengths and establish the upper and lower limits for the wavelength selection criterion. We discuss the validity of the visualization method for the measurement of the wavelength and frequency using a simple analytical model of the streaklines. \textcopyright{} 1996 The American Physical Society.

Acoustic characteristics of less‐masculine‐sounding male speech

Abstract: This study compared samples of less‐masculine‐sounding (LMS) and more‐masculine‐sounding (MMS) male speech to identify acoustic characteristics, other than fundamental frequency, that might contribute to the perception of these categories. In the first phase, audiorecorded speech samples provided by 35 males were presented to 35 female listeners in a paired‐comparison perceptual experiment. Nineteen of the male speech samples were judged reliably to fall within the LMS or MMS categories. Within those 19 samples, 8 speakers (4 LMS and 4 MMS) exhibited similar distributions of habitual fundamental frequency values in connected speech and in sustained phonation. In the second phase of the experiment, various acoustic measures of these eight connected speech samples were conducted. Significant differences between measures of fundamental frequency contours, vowel formant midpoint values, and in the first, third and fourth spectral moments of two fricatives were revealed. These findings may be useful in creatin...

Vibration of geometrically imperfect panels subjected to thermal and mechanical loads

Abstract: The results of a study of the vibration response of transversely isotropic flat and curved panels subjected to temperature fields and to mechanical loads into the postbuckling load range are presented. The results were obtained using a higher-order transverse-shear-deformation theory of shallow shells that includes the effects of geometric nonlinearities and initial geometric imperfections. The results focus on the interaction between the temperature field, the applied mechanical load, and the fundamental frequency associated with small vibrations about the prebuckling and postbuckling equilibrium states. Results are presented for a wide range of temperatures and mechanical load magnitudes and of geometric parameters. The results show that transverse-shear flexibility has a significant effect on the analytical prediction of panel response and that the fundamental frequency of a panel may be substantially overestimated in the prebuckling load range and underestimated in the postbuckling load range. Results are also presented that indicate that the fundamental frequency of flat panels generally increases as the initial geometric imperfection amplitude increases for both the prebuckling and postbuckling load ranges. The results, however, also indicate that the fundamental frequency of curved panels generally decreases in the prebuckling load range and increases in the postbuckling load ranges.

Method and system for controlling combustion engines

Abstract: The invention relates to a method and system for controlling combustion engines by detection of the present air/fuel ratio within the cylinders of the combustion engine, using an analysis of the characteristics of the ionisation current, as detected via a measuring gap with a bias voltage applied being arranged in the combustion chamber, preferably using the spark plug gap in an Otto-engine. A measuring voltage corresponding to the degree of ionisation is detected during the flame ionisation phase and during a time- or crankshaft position dependent period A, B, C or D, which duration is dependent of the present air/fuel ratio, and at finally will be finished by an amplitude maximum PF during the flame ionisation phase. A parameter characteristic for the fundamental frequency of the measuring voltage during the period A, B, C or D is detected, which parameter indicates a tendency towards the rich direction of stochiometric when the fundamental frequency increases, and inversely indicates lean tendency when the fundamental frequency decreases. The fundamental frequency is preferably detected from the differential value of the measuring voltage during the period A, B, C or D, in respect of time t or crankshaft degrees VC, dUION/dt respectively dUION/dVC. The differential value multiplied with a constant is used at least partly when determining a relative or absolute air/fuel ratio.

A laterally driven micromachined resonant pressure sensor

Abstract: A new type of resonant pressure sensor is presented which employs a laterally driven resonant strain gauge. The resonant strain gauge is designed using simple linear elastic theory and the sensor fabricated by a combination of bulk- and surface-micromachining techniques. The strain gauge is driven electrostatically and the resultant vibration sensed capacitively. Its lateral mode of oscillation offers several advantages, such as a Q-factor insensitive to the leakage of cavity gases. The resonator has been designed to have a fundamental frequency of 52 kHz and a gauge factor of 60 Hz μN−1. Preliminary measurements of devices yield a fundamental frequency of 52 ± 15 kHz, a Q-factor in air of 50 and a pressure sensitivity of 8.8 kHz bar−1.

Phase control of absorption in large polyatomic molecules

Abstract: The phenomenon of interference of the amplitude for absorption of one photon of frequency 3ω and the amplitude for absorption of three photons of frequency ω was theoretically predicted by Shapiro, Hepburn, and Brumer. The interference was demonstrated experimentally by varying the relative phase between the tripled frequency photon and three photons with the fundamental frequency by the groups of Elliott and Gordon in atoms and small molecules. In order to see how general this phenomenon is, five compounds were studied, ammonia, trimethylamine, triethylamine, cyclooctatetraene, and 1,1‐dimethylhydrazine. CH3I was used as the tripling gas for light in the range 604–600 nm. Interference was observed in all cases. The last four compounds have low ionization potentials and interference was observed between a 3+1 and a 1+1 ionization process with a maximum modulation of 22%. NH3 with a higher ionization potential requires absorption of 3+2 or 1+2 photons and exhibits a maximum modulation of 33%. We conclude that molecular size is no obstacle and that as long as a molecule has sufficiently strong absorption at the tripled frequency, and sufficient vapor pressure, and the laser fundamental beam is very strong, phase control of interference is observable.

Multi-mode resonances in fluids

Abstract: When a lightly damped fluid resonator is forced near its fundamental frequency, the most usual response is one in which the fluid oscillates in the corresponding eigenmode with an amplitude response similar to that of a Duffing oscillator. Examples are the sloshing of a horizontally oscillated tank or acoustic oscillations in a resonator of general shape. However, multiple eigenmodes can be excited if the spectrum is either commensurate or degenerate and both acoustic resonance and the sloshing of shallow water in a nearly square container exemplify both these exceptional cases. In this paper we investigate how the response of such systems depends on geometry and dispersion.

Aliasing sampler for plasma probe detection

Abstract: An aliasing sampler probe (22, Fig 1) for detecting plasma RF voltage and current employs a sampling signal with a sampling rate slower that the RF fundamental frequency selected to produce an aliasing waveform at an aliasing frequency that is several orders of magnitude below the RF fundamental frequency In one embodiment, the RF power is applied at 1356 MHz (Fig 3A), and sampling pulses have a sampling rate of 2732 MHz (Fig 3B) to produce replicas of the RF voltage and current waveforms (Fig 4) at an aliasing frequency of about 100 KHz The aliasing replicas preserve phase and harmonic information with an accuracy that is not available from other sampling techniques

Communications method and apparatus for digital information

Abstract: A method and apparatus for single signal, multiple channel digital information transfer through pulses with time slot allocation. The apparatus consists of one or more transmitting devices and one or more receiving devices. Multiple source signals are each allocated a unique time slot between successive synchronization pulses. Digital signals from each source are converted to analog information pulses synthesized from a combination of a fundamental frequency wave and a finite number of its harmonics. The total signal, which consists of successive synchronization pulses interspersed with information pulses for each signal source, each within its allocated time slot, is transmitted to the receivers. Each receiving device extracts the fundamental frequency and harmonic components through the use of narrow bandpass, high Q filters for each information pulse in its time slot and uses the known algorithm to reproduce the input digital signals. One or more of the harmonic components may be used for transmitting a reference calibration signal.

Doppler triangulation transmitter location system

Abstract: In a system for locating the position of a transmitter, a platform containing an antenna is moved through a measurement path. The frequency received by the antenna is measured at measurement points distributed along a measurement path. The frequency is measured by cross correlating coherent pulses of the received frequency signal. An inertial navigation system on the platform indicates the position of the measurement path. A computer determines estimated locations by non-linear least squares convergence starting from trial locations. The non-linear least squares convergence is based on the frequency equation for the received frequency ##EQU1## in which f 0 is the transmitter frequency, V is the antenna velocity and r is the range of the transmitter. The computer evaluates a cost function derived from the frequency equation, for each location estimated by the non-linear least squares convergence and selects the estimated location with the lowest cost function as the best solution.

A new computer-aided method for the efficiency measurement of low-loss transformers and inductors under nonsinusoidal operation

Abstract: The measurement of voltages, currents and losses of saturated magnetic devices under nonsinusoidal conditions is not well understood, because the principle of superposition does not apply. The complexity of the task is increased by the fact that internally generated harmonic currents can be compensated by externally applied currents of either the same harmonic frequency or of other harmonic frequencies. In other words, a transformation of fundamental power to harmonic power, and vice versa, takes place. In addition the flux-density waveshape varies-and therefore also the iron-core losses-as the harmonic phase shift of the externally applied harmonic voltage changes, although the percentage of the harmonic amplitude remains constant. It is the first objective of this paper to assemble a computer-aided testing circuit which enables the investigation of the variation of the iron-core losses with the amplitude of the fundamental flux density B/spl circ//sub 1/, the amplitude of the /spl nu//sup th/ harmonic B/spl circ//sub /spl nu//, the harmonic order /spl nu/ and the phase shift /spl phi//sub /spl nu//of the /spl nu//sup th/ harmonic with respect to the fundamental. Phase-factor functions-which reflect the dependency of the iron-core losses on the harmonic phase shift /spl phi//sub /spl nu//-are directly measured for given Epstein frame iron-core samples. Thereafter, the effect of these newly defined phase-factor functions on the total transformer losses is demonstrated. The attenuation of low-frequency (60 to 3,000 Hz) flux-density harmonics in inductors is determined, if the core is biased with fundamental flux density.

Frequency ratios of spectral components of musical sounds

Abstract: A recently developed high resolution frequency tracker [J. C. Brown and M. S. Puckette, ‘‘A high resolution fundamental frequency determination based on phase changes of the fourier transform,’’ J. Acoust. Soc. Am. 94, 662–667 (1993)] has made it possible to measure the ratios of the frequencies of the upper harmonics of a sound with respect to its fundamental frequency with high accuracy. Calculations were carried out on digitized sounds produced by a clarinet, alto flute, voice, piano, violin, viola, and cello. The sounds produced by the stringed instruments included examples played pizzicato and bowed both with and without vibrato. Measured ratios were exactly equal to integers for all instruments except the piano and strings played pizzicato. Anomalous behavior was observed for the fundamental frequency for vibrato sounds played by stringed instruments with the frequency deviation exceeding the extrema of the other harmonics divided by their harmonic number by about 1% on average. Piano inharmonicity ...

On-line tracking of changing harmonics in stressed power systems: application to Hydro-Quebec network

Abstract: This paper applies, to a practical test case, two schemes for determining harmonics in power systems that are not limited to stationary waveforms, but can equally estimate harmonic phasors in waveforms with time-varying amplitudes and changing fundamental frequency. The first scheme relies on the short-time Fourier analysis performed using the fast Fourier transform (FFT) with time-domain windowing and frequency-domain interpolation. Another scheme combines fundamental-frequency tracking with a Kalman filter-based harmonic analyzer, yielding a uniformly sampled, self-synchronizing harmonics tracker. The performance of these advanced measurement schemes for changing harmonics is illustrated convincingly on nonstationary waveforms generated in the EMTP using a realistic series-compensated transmission network.

Robust method of measurement of fundamental frequency by ACLOS: autocorrelation of log spectrum

Abstract: Correct and robust measurement of fundamental frequency F/sub 0/ is requested in the analysis of speech sound, speech enhancement systems and analysis synthesis telephony employing F/sub 0/. This article proposes a new method to estimate F/sub 0/ utilizing the autocorrelation function of the log spectrum. This method is named ACLOS (autocorrelation of log spectrum). In this method, the fundamental frequency is estimated from the peak of the autocorrelation function along the frequency axis of the spectral pattern. It means that F/sub 0/ is measured by enhancing the periodic feature of harmonics on the spectrum. Experimental results indicate that ACLOS gives more robust and reasonable pitch information than other methods give.

Ultrasonic treatment device

Abstract: PROBLEM TO BE SOLVED: To improve the safety and certainty of a treatment by receiving the echo of first ultrasonic waves from an ultrasonicwave-for-treatment generation source and the echo of second ultrasonic waves from an ultrasonic probe and constituting the intensity distribution of the ultrasonic waves for the treatment based on reception signals. SOLUTION: The ultrasonic waves for the intensity distribution are cyclically generated from the ultrasonic-wave-for-treatment generation source 2 in a band whose center is a first fundamental frequency and the echo of the ultrasonic waves for the intensity distribution is received by a probe 16 for imaging. The piezo element of the probe 16 for imaging is highly sensitive for both of the first fundamental frequency of the ultrasonic waves for the intensity distribution and the second fundamental frequency of the ultrasonic waves for imaging. Since the intensity distribution is imaged based on lower harmonic components largely included in the echo of the ultrasonic waves for the intensity distribution, the intensity distribution faithful to the actual intensity distribution is obtained and judgement such as the estimation or the like of a heat generation area or the like is highly accurately performed based on the intensity distribution.

80 GHz AlGaAs HBT oscillator

Abstract: This paper describes an 80 GHz monolithic fundamental frequency oscillator using an AlGaAs heterojunction bipolar transistor technology. The transistor performs a unity current gain frequency f/sub T/=130 GHz and a maximum frequency of oscillation f/sub max/=180 GHz. The output signal level of the oscillator is -9 dBm, and the SSB phase noise is estimated as -80 dBc/Hz at 1 MHz offset frequency. A couple of coplanar waveguides are utilized for resonators.

Multiple-scattering effects in the second-harmonic generation of light in reflection from a randomly rough metal surface.

Abstract: We present a rigorous numerical simulation analysis of the second-harmonic generation of p-polarized light in reflection from a one-dimensional, randomly rough, metal surface when the plane of incidence is perpendicular to the generators of the surface. When the incident light cannot couple to surface electromagnetic waves supported by the metal surface at the fundamental frequency, the angular distribution of the intensity of the incoherent component of the scattered light at the harmonic frequency displays either well-defined peaks or dips in the retroreflection direction and in the direction normal to the mean plane of the surface. These effects are suppressed by the direct excitation of surface polaritons at the fundamental frequency.

A comparison of several recent methods of fundamental frequency and voicing decision estimation

Abstract: The authors are interested in the comparison of several kinds of methods for fundamental frequency estimation and GCI (glottal closure instant) detection. These methods operate in various domains (time-, frequency- or joint time-frequency domains). Their performances have been compared for both fundamental frequency estimation and voicing decision tasks as well as GCI detection, when applicable. This comparison was designed to be as unbiased as possible, so as to reflect the intrinsic properties of each method. A method based on a "Born-Jordan" kernel bilinear time-frequency representation of speech signals achieves the best performance in terms of GCI detection accuracy but is not as robust to inter-speaker variability as the SIFT algorithm. An auditory model, which has been applied on the same data in a previous study has been shown to compare favourably to other methods (such as SIFT) in adverse noisy conditions only.

Free and forced vibrations of a spinning viscoelastic beam

Abstract: The free and forced response of spinning, viscoelastic, Rayleigh shafts is studied. Viscoelasticity is included using the three parameter solid model. The closed form polynomial frequency equation and integral expressions for the response to a general forcing function are derived. A convenient decay parameter is described. Results are given for natural frequencies and decay rates as functions of shaft rotation speed, stiffness, and viscosity. It is found that shaft materials are possible which have desirable damping and natural frequency characteristics. A parameter case is discussed in which natural frequency and damping simultaneous increase, while stiffness is held constant. Also, the special case of forced response to a step load is derived and used to illustrate the combined effects of viscoelasticity and gyroscopic forces.

Coherent control in four-photon excitation schemes

Abstract: We report the observation of coherent control of the ionization rate in four-photon resonant, five-photon ionization schemes in Kr and Xe. The intermediate resonance is excited via different interfering channels involving four-photon absorption of the fundamental laser frequency ( ionization) as well as one third harmonic and one fundamental frequency photon absorption ( excitation), a particular aspect of the scheme being that interference occurs at a virtual level. By varying the relative phase of the two electromagnetic fields, a large modulation depth has been observed which is due to the chosen non-linear excitation scheme. In the Xe excitation experiment the interference between the different channels could be additionally probed through the modulation of the third-harmonic signal.

Frequency–temperature relations of thickness‐shear and flexural vibrations of contoured quartz resonators

Abstract: The two‐dimensional first‐order equations of incremental vibrations superposed on the steady and homogeneous thermal deformations of crystal plates by Lee and Yong are reduced to a set of four coupled equations for frequencies up to and including those of the fundamental x1x2 (or slow) thickness‐shear mode. These equations are employed to study the frequency–temperature relations of the thickness‐shear and flexural vibrations of beveled plates of AT cut of quartz. Closed form solutions for the uniform portion and analytical solutions in terms of infinite power series for the contoured portions are obtained. By requiring these solutions to satisfy the continuity conditions and traction‐free edge conditions, the frequency equation is obtained. Effects of the contouring and the orientation angle of the plate are examined systematically by computing the frequency changes as a function of temperature increment for various values of geometric parameters and the orientation angle of the plate. Similar results fo...

Localization by harmonic structure and its application to harmonic sound stream segregation

Abstract: Sound stream segregation is essential for understanding auditory events in the real-world. In this paper, we present a new method for sound stream segregation using harmonic structure and localization, or direction, in the horizontal plane. The direction of the sound source is determined by using the harmonic structure extracted from binaural inputs. The fundamental frequency of each sound is then refined by using the direction of its source. This paper discusses how the effectiveness of the harmonic-based stream segregation system (HBSS) is improved by incorporating the new method and presents the binaural HBSS (Bi-HBSS). In particular, experimental results show that the Bi-HBSS reduces the spectrum distortions and the fundamental frequency errors, compared with the HBSS and with a direction-based stream segregation system.