Showing papers on "Fundamental frequency published in 1997"

Ultrasonic diagnostic imaging of response frequency differing from transmit frequency

Abstract: An ultrasonic diagnostic imaging system and methods are described which produces ultrasonic images from harmonic echo components of a transmitted fundamental frequency. Preferably, a programmable digital filter is used to pass harmonic echo components for image processing to the exclusion of fundamental frequency signals. In a preferred embodiment, artifacts are removed by producing decorrelated replicas of the harmonic signals, which are then combined and used for imaging. To produce an image in the presence of depth dependent attenuation of high frequency echo signals, both fundamental and harmonic echo signals are processed and used to produce an image blended from components of both fundamental and harmonic echo signals.

Harmonic modelling of non-linear load by means of crossed frequency admittance matrix

Abstract: An alternative harmonic model for representing power system nonlinear loads by a "crossed-frequency" admittance matrix is presented in the paper. This harmonic model is applicable to passive and stationary electrical loads assuming a constant fundamental frequency voltage. Results of the proposed harmonic model are reported and compared with experimental tests.

Ultrasound imaging method and system for transmit signal generation for an ultrasonic imaging system capable of harmonic imaging

Abstract: An improvement to the method for harmonic imaging including the steps of (a) transmitting ultrasonic energy at a fundamental frequency and (b) receiving reflected ultrasonic energy at a harmonic of the fundamental frequency is provided. For the improvement, the transmitting step includes the step of transmitting a uni-polar waveform or a waveform characterized by an amplitude change rate of 8 or fewer times pre carrier cycle, said waveform comprising an envelope shape rising gradually to a respective maximum value and falling gradually from the respective maximum value.

Method and apparatus for measuring pressure in a coriolis mass flowmeter

Abstract: A method for determining pressure in an operating Coriolis effect mass flowmeter (10). The Coriolis flowmeter flow tubes (130, 130') are vibrated in both a bending mode (as is normal for measuring mass flow rate) and in a twisting mode. The ratio of the fundamental frequencies at which the flow tubes vibrate in each of the two vibration modes is proportional to the pressure within the flow tubes. In the preferred embodiment, a sum/difference method initially isolates the superposed sinusoids representing the fundamental frequencies of the two vibrational modes. Fast conjugate gradient (FCG) digital filters (512, 514) are then used to rapidly estimate the fundamental frequencies in each of the two vibration modes. The estimated frequencies are then used by filter chains including digital notch (518, 508) and band pass filters (506, 1520) as well as recursive maximum likelihood (RML) digital filter (510, 522) techniques to enhance the bending mode and twisting mode fundamental frequency estimates. The enhanced bending mode andtwisting mode frequency estimates are used to determine the pressure within the flow tubes as a function of the ratio of the two frequencies as well as to center the notch and band pass filter chains used to enhance the bending mode frequency of the two vibration sensor channels for mass flow rate computations. The pressureso determined may then be used to correct mass flow rate computations or for other pressure measurement purposes per se.

Solitary waves in quadratically nonlinear resonators

Abstract: We identify two-dimensional stable and unstable bright solitary waves or localized structures in a planar resonator with a quadratically nonlinear medium driven by a field at the fundamental frequency only. These waves are extremely localized while the nonlocal interaction between the fundamental and second harmonics prevents a collapse. To a certain extent they can be regarded as residuals of coexisting hexagon patterns.

Method and system for enhancing quality of sound signal

Abstract: An apparatus for conveying to a listener a pseudo low frequency psycho-acoustic sensation (Pseudo-LFPS) of a sound signal, including: frequency unit capable of deriving from the sound signal high frequency signal and low frequency signal (LF signal) that extends over a low frequency range of interest. Harmonics generator coupled to the frequency generator and being capable of generating, for each fundamental frequency within the low frequency range of interest, a residue harmonic signal having a sequence of harmonics. The sequence of harmonics, generated with respect to each fundamental frequency contains a first group of harmonics that includes at least three consecutive harmonics from among a primary set of harmonics of the fundamental frequency. Loudness generator coupled to the harmonics generator and being capable of bringing the loudness of the residue harmonic signal to match the loudness of the low frequency signal. Summation unit capable of summing the residue harmonic signal and the high frequency signal so as to obtain psychoacoustic alternative signal.

Speech analysis and synthesis using an AM-FM modulation model.

Abstract: In this paper, the AM‐FM modulation model is applied to speech analysis, synthesis and coding. The AM‐FM model represents the speech signal as the sum of formant resonance signals each of which contains amplitude and frequency modulation. Multiband filtering and demodulation using the energy separation algorithm are the basic tools used for speech analysis. First, multiband demodulation analysis (MDA) is applied to the problem of fundamental frequency estimation using the average instantaneous frequency as estimates of pitch harmonics. The MDA pitch tracking algorithm is shown to produce smooth and accurate fundamental frequency contours. Next, the AM‐FM modulation vocoder is introduced, which represents speech as the sum of resonance signals. A time-varying filterbank is used to extract the formant bands and then the energy separation algorithm is used to demodulate the resonance signals into the amplitude envelope and instantaneous frequency signals. EAcient modeling and coding (at 4.8‐9.6 kbits/sec) algorithms are proposed for the amplitude envelope and instantaneous frequency of speech resonances. Finally, the perceptual importance of modulations in speech resonances is investigated and it is shown that amplitude modulation patterns are both speaker and phone dependent. ” 1999 Elsevier Science B.V. All rights reserved. Zusammenfassung

Multi axle order tracking with the Vold-Kalman tracking filter

Abstract: The Vold-Kalman filter allows for the high performance simultaneous tracking of orders in systems with multiple independent axles. The interactions associated with close and crossing orders give rise to beating and complex psychoacoustic phenomena. With this new filter and using multiple tachometer references, waveforms as well as amplitude and phase may be extracted without the beating interactions that are associated with conventional methods. The Vold-Kalman filter provides several filter shapes for optimum resolution and stopband suppression. Orders extracted as waveforms have no phase bias and may, therefore, be used in synthesis and tailoring. Vold and Leuridan 1 in 1993 introduced an algorithm for high resolution, slew rate independent order tracking based on the concepts of Kalman filters. 9,10 The algorithm has been highly successful as implemented in a commercial software system in solving data analysis problems previously intractable with other analysis methods. At the same time certain deficiencies have surfaced, prompting the development of an improved formulation. This article presents the new Vold-Kalman algorithm and some of its applications in the Bruel & Kjaer PULSE, MultiAnalyzer system. 5 Order tracking is the art and science of extracting the sinusoidal content of measurements from acousto-mechanical systems under periodic loading. Order tracking is used for troubleshooting, design and synthesis. Each periodic loading produces sinusoidal overtones, or orders, or harmonics, at frequencies that are multiples of that for the fundamental tone. The orders may be regarded as amplitude modulated carrier waves that frequency hop. Many practical systems have multiple axles that may run coherently through locked up transmissions, may be partially related through belt slippage and control loops, or may run independently, such as when a cooling fan cycles in an engine compartment. The Vold-Kalman algorithm allows for the simultaneous estimation of multiple orders, effectively decoupling close and crossing orders. This is especially important for acoustics applications, where order crossings cause transient beating events. The new algorithm allows for a much wider range of filter shapes, such that signals with sideband modulations are processed with high fidelity. Finally, systems subject to radical RPM changes, such as transmissions, are also tracked through the transient events associated with abrupt changes in inertia and boundary conditions. The order functions are extracted without phase error, and may then be used in synthesis applications for sound quality and laboratory simulations.

Analysis of accumulated timing jitter in the time domain

Abstract: This paper deals with the effects of accumulated timing-jitter on the signal-to-noise ratio (SNR) of real sine waves. Such a problem was recently investigated by the author, using the discrete-Fourier method. However, the frequency-domain analysis has some limitations due to the fact that some of the accumulated timing-jitter noise power, found at the fundamental frequency component, would be added to the power of the input signal itself. Thus, in this paper, the analysis is performed in the time-domain and is restricted to the SNR measurement. An expression for the SNR in terms of timing-jitter distribution parameters, and the number of samples of the input signal, is developed. Computer simulations are presented, which showed excellent agreement with the developed expression. Also, a comparison between the results obtained from the time-domain analysis and the frequency-domain, is presented.

Method of transforming periodic signal using smoothed spectrogram, method of transforming sound using phasing component and method of analyzing signal using optimum interpolation function

Abstract: At a smoothing spectrogram calculation portion, a triangular interpolation function having a frequency width twice that of the fundamental frequency of a signal is obtained based on information on the fundamental frequency of the signal. The interpolation function and a spectrum obtained at an adaptive frequency analysis portion are convoluted in the direction of frequency. Then, using a triangular interpolation function having a time length twice that of a fundamental period, the spectrum interpolated in the frequency direction described above is further interpolated in the temporal direction, in order to produce a smoothed spectrogram having the space between grid points on the time-frequency plane filled with the surface of a bilinear function. Using the smoothed spectrogram, a speech sound is transformed. Therefore, the influence of periodicity in the frequency direction and the temporal direction can be reduced.

Determination of the nonlinear ultrasonic parameter ? using a Michelson interferometer

Abstract: We describe an accurate optical technique for determining the nonlinear ultrasonic parameter . Our technique uses a path-stabilized Michelson laser interferometer, in contrast to more conventional methods which use piezoelectric or capacitive detectors. Features include high spatial resolution (typically ), flat bandpass response over a wide range (> 30 MHz) and simple self-calibration. We demonstrate the technique using a fused silica disc 19.15 mm thick and a fundamental frequency of 10 MHz. For comparison, was also obtained for the same specimen using capacitive and piezoelectric detectors. Errors and correction factors for all three methods are discussed; in particular, we note the importance of including ultrasonic diffraction effects. When such corrections are applied, we obtain the following results: , and . These values are in reasonable agreement with each other as well as with published values of .

Draft revision of IEEE STD 1139-1988 standard definitions of physical quantities for fundamental, frequency and time metrology-random instabilities

Abstract: This is a draft revision of IEEE Std 1139-1988 Standard Definitions of Physical Quantities for Fundamental Frequency and Time Metrology. This draft standard covers the fundamental metrology for describing random instabilities of importance to frequency and time metrology. Quantities covered include frequency, amplitude, and phase instabilities; spectral densities of frequency, amplitude, and phase fluctuations; variances of frequency and phase fluctuations; time prediction; and confidence limits when estimating the variance from a finite data set. The standard unit of measure for characterizing phase and frequency instabilities in the frequency domain is L(f), defined as one half of the double-sideband spectral density of phase fluctuations. In the time domain, the standard unit of measure of frequency and phase instabilities is the fully overlapped Allan deviation /spl sigma//sub y/(/spl tau/) or the fully overlapped modified Allan deviation Mod /sub /spl sigma//(/spl tau/).

Transverse Vibration of a Simply Supported Beam with Symmetric Overhang of Arbitrary Length

Abstract: The numerical solution to the frequency equation for the transverse vibration of a simple beam with symmetric overhang is found. The numerical results converge to the analytical solutions for the two limiting cases of a beam with no overhang and a beam with no span and agree with the case in which the supports are at the nodal points of a freely vibrating beam. An approximation to the solution of the frequency equation for beams with small overhang is presented and compared to the numerical solution. This simple yet accurate approximation is most useful to determine a beam's flexural stiffness, EI, or modulus of elasticity, E, by freely vibrating a simply supported beam.

Infants' pitch perception: masking by low- and high-frequency noises.

Abstract: The present research employed an operant conditioning procedure typically used with infants to test noise masking of pure tones and tonal complexes in adults and in 7-month-old infants. Adults and infants were presented with either pure tones of 160 and 200 Hz or harmonic tonal complexes with pitches equivalent to 160 and 200 Hz. The tonal complexes did not contain energy at the fundamental frequency. After learning these tasks, subjects in the tonal complex group categorized spectrally varying tonal complexes according to the pitch of the missing fundamental. Stimuli were subsequently presented in combination with either a low- or a high-frequency noise. Both age groups successfully discriminated pure tones when combined with a high-frequency noise but not when combined with a low-frequency noise in the same frequency range as the pure tone. Infants, like adults, successfully categorized harmonic tonal complexes based on the pitch of the missing fundamental when those stimuli were combined with a low-frequency noise in the range of the missing fundamental but not when combined with a high-frequency noise which covered the frequency range of the harmonics themselves. These results suggest that infants rely primarily on a central process and not peripherally generated combination tones to hear the pitch of the missing fundamental.

Sinusoidal Voltammetry for the Analysis of Carbohydrates at Copper Electrodes

Abstract: A digital approach for the collection and analysis of electrochemical frequency domain spectra is presented for the oxidation of carbohydrates at a copper electrode using a continuous, large-amplitude sine wave as an excitation waveform. The background charging current response is a phase-shifted sine wave with the major frequency component concentrated at the fundamental frequency. A nonlinear faradaic response due to the oxidation of sugars produces significant signal intensities at the higher harmonics as well as the fundamental frequency. Examination of the frequency spectra of glucose and maltose leads to selective and sensitive detection of these sugars at a copper electrode. The selectivity of this measurement relies on the inherent difference in the frequency domain spectra (i.e., magnitude and phase of each harmonic) of sugars of different sizes. This frequency distribution is dramatically affected by temperature, indicating the effect of kinetics in the mechanism for the oxidation of sugars. The...

Psychoacoustical evaluation of the pitch-synchronous overlap-and-add speech-waveform manipulation technique using single-formant stimuli

Abstract: This article presents two experiments dealing with a psychoacoustical evaluation of the pitch synchronous overlap-and-add (PSOLA) technique. This technique has been developed for modification of duration and fundamental frequency of speech and is based on simple waveform manipulations. Both experiments were aimed at deriving the sensitivity of the auditory system to the basic distortions introduced by PSOLA. In experiment I, manipulation of fundamental frequency was applied to synthetic single-formant stimuli under minimal stimulus uncertainty, level roving, and formant-frequency roving. In experiment II, the influence of the positioning of the so-called “pitch markers” was studied. Depending on the formant and fundamental frequency, experimental data could be described reasonably well by either a spectral intensity-discrimination model or a temporal model based on detecting changes in modulation of the output of a single auditory filter. Generally, the results were in line with psychoacoustical theory on the auditory processing of resolved and unresolved harmonics.

Dynamic Response of Equipment in Structures with Sliding Support

Abstract: The dynamic behaviour of a single degree-of-freedom (DOF) equipment mounted on a sliding primary structures subjected to harmonic and earthquake ground motions is studied numerically. To deal with the discontinuity nature of sliding structural systems, in this work the fictitious spring model is adopted. With the problem formulated in a state space form, an incremental numerical scheme capable of dealing with multi-DOF sliding structural systems is proposed for solving the time history responses. Numerical examples excited by harmonic and real earthquake ground motions are considered in order to study the following three effects: (1) the variation of the frictional coefficient of the sliding support, (2) subharmonic resonance and (3) effect of tuning (i.e. when the frequency of the equipment is coincident with or close to the fundamental frequency of the primary structure) on the mounted equipment. The dynamic characteristics of the mounted equipment are highlighted in the analysis of the numerical examples.

Temporal processing of pitch in the auditory system

Abstract: In order to understand our ability to perceive music, we have to understand how our auditory neurons process acoustic signals It is demonstrated here that temporal processing mechanisms in the auditory brainstem are essential for important aspects of musical perception, like the perception of pitch Neurophysiological experiments revealed that the temporal feature important for pitch is the periodicity of signal envelopes The corresponding evidence from neurophysiological, anatomical, and psychophysical experiments will be summarized The envelope periodicity corresponds to the fundamental frequency of signals and reflects periodic vibrations of sound sources As a consequence of the cochlear analysis, periodicity is represented not only in the firing patterns of auditory nerve fibers which code the fundamental frequency, but also in those which are involved in the spectral coding of overtones In the brainstem intrinsic neuronal oscillations, temporal integration, and coincidence detection con

Real-time frequency domain temperature and oxygen sensor with a single optical fiber

Abstract: The combined excited-state phosphorescence lifetimes of an alexandrite crystal and platinum tetraphenylporphyrin Pt(TPP) in a single-fiber sensor are used to monitor temperature and oxygen concentration in the physiological range from 15-45/spl deg/C and 0-50% O/sub 2/ with precision of 0.24/spl deg/C and 0.15% O/sub 2/ and accuracy of 0.28/spl deg/C and 0.2% O/sub 2/. A 500-/spl mu/m cubic alexandrite crystal bound to the distal end of a 750-/spl mu/m-diameter optical fiber core and the Pt(TPP) coated circumferentially with a length of 1 cm from the end of the same fiber are excited with pulsed super-bright blue LED light. This apparatus uses a 125-kHz sampler for data acquisition and frequency domain methods for signal processing. The instrument amplifies both the dc and ac components of the photomultiplier output and band limits the signal to 20 kHz. The fundamental frequency of the excitation is set to 488.3 Hz and the highest harmonic used is the 35th. This bandlimited signal is sampled and averaged over a few hundred cycles in the time domain. The frequency domain representation of the data is obtained by employing fast Fourier transform algorithms. The phase delay and the modulation ratio of each sampled harmonic are then computed. At least four log-spaced harmonic phases or modulations are averaged before decoding the two lifetimes of temperature and oxygen phosphorescent sensors. A component of zero lifetime is introduced to account for the excitation backscatter leakage through optical interference filters seen by the photodetector. Linear and second-order empirical polynomials are employed to compute the temperatures and oxygen concentrations from the inverse lifetimes. In the situation of constant oxygen concentration, the lifetime of Pt(TPP) changes with temperature but can be compensated using the measured temperature lifetime. The system drift is 0.24/spl deg/C for the temperature measurement and 0.59% for the oxygen concentration measurement over 30 h of continuous operation. The instrumentation and methods allow for 6-s update times and 90-s full-response times.

Real-time fundamental frequency estimation by least-square fitting

Abstract: For real-time applications, a fundamental frequency estimation algorithm must be able to obtain accurate estimates from short signal segments. Characterization of the error function of fitting a sinusoid to the signal segment allows its spectrum to be deduced and the algorithm to be implemented efficiently. Musical signals are discussed in particular.

Measuring internal electric fields in organic light‐emitting diodes using electroabsorption spectroscopy

Abstract: A widely applicable electroabsorption technique to measure internal electric fields in organic light-emitting diodes is presented The technique exploits the change in the ac electroabsorption response in the presence of a dc electric field The electroabsorption signal is modulated at the fundamental frequency of the ac test signal, in addition to the usual modulation at the second harmonic frequency, when a dc bias is present In metal/organic film/metal devices employing different metal contacts there is a built-in electric field in the organic film caused by the difference in work function between the two contacts The electroabsorption response at the fundamental frequency of the applied ac bias is measured as a function of an external dc bias The electroabsorption signal is nulled when the applied dc bias cancels the built-in electric field established by the different metals We apply this technique to measure changes in metal–polymer Schottky barrier heights as a function of the contact metal In metal/multiple organic films/metal structures the electroabsorption signals from the constituent organic films are identified spectroscopically and measured at both the fundamental and second harmonic frequency of the ac test signal The amplitudes of the electroabsorption responses are then used to determine the ac and dc electric fields present in the organic layers We apply this technique to determine the dc electric field distribution within a multi-layer organic light-emitting diode These results highlight the general applicability of electroabsorption methods to probe internal electric fields in organic light-emitting diodes © 1997 John Wiley & Sons, Ltd

A new PWM method to reduce beat phenomenon in large capacity inverters with low-switching frequency

Abstract: In an asynchronous pulsewidth modulation (PWM) method, the ratio of the carrier frequency to the fundamental frequency must be at least 15-20 in order to suppress the beat phenomenon. However, it is impossible to achieve this condition for large-capacity inverters (e.g., gate-turn-off thyristor inverters), when the fundamental frequency is high. Assuming that the beat phenomenon is caused by an error generated in the PWM process, the authors have introduced a compensator to reduce the error. As a result, beat phenomenon can be decreased for a low carrier frequency. Effectiveness of the proposed method is shown by experimental results.

Method and apparatus for reducing harmonic distortion

Abstract: The present invention relates to a control system for a vibrator system capable of generating and applying a reciprocating force to an object, such as the underlying ground or water. The control system is generally provided with a means for outputting a drive signal having a fundamental frequency to the vibrator system to activate the reciprocating of the base plate of the vibrating system and a means for receiving a vibrator output signal indicative of the force applied to the object. The vibrator output signal includes at least one harmonic frequency signal and is delayed with respect to the phase of the initial drive signal. To increase the signal-to-noise ratio of the vibrator system, the control system includes a harmonic distortion reduction means receiving the vibrator output signal for outputting at least one harmonic drive signal to the vibrator system. The harmonic drive signal has a proper phase, amplitude, polarity, and frequency which are adjusted to minimize at least one of the harmonic frequency signals being produced by the vibrator system.

Method for igniting high frequency operated, high intensity discharge lamps

Abstract: The present invention describes a method and circuitry for igniting high frequency operated, high intensity discharge lamps by means of a dual resonant circuit driven by a nonsinusoidal waveform; typically a square wave in the preferred embodiment. A capacitor in series with the lamp is selected to resonate at the fundamental frequency of the applied waveform when the lamp is in the on condition, providing thereby the high frequency power to the lamp for its normal operation. A capacitor in parallel with the lamp is chosen to resonate at a higher harmonic of the applied frequency, typically the third harmonic, when the lamp is in the off condition. Hysteresis heating causes the ignition voltage of the lamp to decrease as higher frequency power is applied, leading to ignition of the lamp at the third harmonic without applying to the lamp one or more pulses of high voltage. An alternative embodiment of the present invention uses dc offset circuitry to apply dc voltage to the lamp at typically an integral multiple of the peak value of the alternating applied voltage.

A DC to X-band frequency doubler using GaAs HBT MMIC

Abstract: An analog frequency doubler is developed using GaAs HBT MMIC technology. In this doubler circuit, a novel push-push circuit configuration is used to provide the efficient frequency conversion and the fundamental frequency rejection over a broad bandwidth. The measurement results of the MMIC demonstrate an average 0 to 3 dB conversion gain and a 10 dB rejection on fundamental frequency up to 14 GHz. Thus, this MMIC can be used as a low-cost insertion block to achieve any stable local-oscillation signals up to X-band by multiplying the high quality VCOs at low frequencies, especially the inexpensive Si BJT based VCOs at wireless frequencies.

A new fundamental frequency modification algorithm with transformation of spectrum envelope according to F/sub 0/

Abstract: This paper proposes a new speech modification algorithm which makes it possible to change the fundamental frequency (F/sub 0/) while preserving high quality. One novel point of the algorithm is that the spectrum envelope is transformed according to amount of F/sub 0/ modification. Based on a codebook mapping formulation, transformation rules are generated using speech data uttered in a different F/sub 0/ range. The rules have two purposes: one is transforming the spectrum envelope of the low frequency band and the other is adjusting the balance between low band power and high band power. The proposed algorithm is applied to a text-to-speech system based on waveform concatenation, and good performance is confirmed by listening tests.

Ultrasonic imaging method and system

Abstract: An ultrasonic imaging system and method provide a composite image having a near-field region and a far-field region that are displayed in a common imaging mode. The near-field region emphasizes received ultrasonic imaging at a harmonic of the fundamental of the transmit waveform, while the far-field region emphasizes received ultrasonic information at the fundamental frequency. In this way the advantages of harmonic imaging are obtained in the near-field without sacrificing penetration performance in the far-field.