Showing papers on "Fundamental frequency published in 2002"

YIN, a fundamental frequency estimator for speech and music

Abstract: An algorithm is presented for the estimation of the fundamental frequency (F0) of speech or musical sounds. It is based on the well-known autocorrelation method with a number of modifications that combine to prevent errors. The algorithm has several desirable features. Error rates are about three times lower than the best competing methods, as evaluated over a database of speech recorded together with a laryngograph signal. There is no upper limit on the frequency search range, so the algorithm is suited for high-pitched voices and music. The algorithm is relatively simple and may be implemented efficiently and with low latency, and it involves few parameters that must be tuned. It is based on a signal model (periodic signal) that may be extended in several ways to handle various forms of aperiodicity that occur in particular applications. Finally, interesting parallels may be drawn with models of auditory processing.

Detecting emotions using voice signal analysis

Abstract: A system and method are provided for detecting emotional states using statistics. First, a speech signal is received. At least one acoustic parameter is extracted from the speech signal. Then statistics or features from samples of the voice are calculated from extracted speech parameters. The features serve as inputs to a classifier, which can be a computer program, a device or both. The classifier assigns at least one emotional state from a finite number of possible emotional states to the speech signal. The classifier also estimates the confidence of its decision. Features that are calculated may include a maximum value of a fundamental frequency, a standard deviation of the fundamental frequency, a range of the fundamental frequency, a mean of the fundamental frequency, and a variety of other statistics.

Basic acoustic properties of microbubbles.

Abstract: Small (encapsulated) gas bubbles in a contrast medium react to an external oscillating pressure field with volume pulsations. Depending on the magnitude of the ultrasound wave, the vibrations will be related either linearly or nonlinearly to the applied acoustic pressure. For low acoustic pressures, the instantaneous radius oscillates linearly in relation to the amplitude of the applied external pressure field. The oscillation of the bubble is governed by parameters such as resonance frequency, damping coefficients, and shell properties. For higher amplitudes of the external field, the pulsation of the bubbles becomes nonlinear. The spectrum of the scattered ultrasound wave also contains higher harmonics of the emitted frequency in addition to the fundamental frequency. The emitted frequency, bubble size, and nonlinear propagation effects have significant influence on the harmonic generation. For encapsulated bubbles exposed to even higher acoustic amplitudes, their scattering effectiveness increases dramatically and becomes transient. The scattered frequency spectrum broadens, containing higher harmonics. This consequence is due to rupture, disappearance, change of gas content, etc. Using these specific characteristics of the contrast bubbles will open new perspectives in imaging and analysis for medical diagnosis.

Bayesian harmonic models for musical pitch estimation and analysis

Abstract: Estimating the pitch of musical signals is complicated by the presence of partials in addition to the fundamental frequency. In this paper, we propose developments to an earlier Bayesian model which describes each component signal in terms of fundamental frequency, partials (‘harmonics’), and amplitude. This basic model is modified for greater realism to include non-white residual spectrum, time-varying amplitudes and partials ‘detuned’ from the natural linear relationship. The unknown parameters of the new model are simulated using a reversible jump MCMC algorithm, leading to a highly accurate pitch estimator. The models and algorithms can be applied for feature extraction, polyphonic music transcription, source separation and restoration of musical sources.

Radial oscillations of encapsulated microbubbles in viscoelastic liquids

Abstract: The small-amplitude radial oscillations of a gas microbubble encapsulated by a viscoelastic solid shell and surrounded by a slightly compressible viscoelastic liquid are studied theoretically. The Kelvin–Voigt and 4-constant Oldroyd models are used to describe the viscoelastic properties of the shell and liquid, respectively. The equation for radial oscillation is derived using the method of matched asymptotic expansions. Based on this equation, we present the expressions for damping coefficients and scattering cross sections at the fundamental frequency and at twice that frequency. The numerical maximization of the amplitude-frequency response function shows that the resonance frequency for the encapsulated microbubble highly depends on viscous damping, and therefore, significantly differs from the undamped natural frequency. The effects of the shell and liquid parameters on the resonance frequency and scattering cross sections are analyzed.

Ultrasonic wave cosmetic device

Abstract: An ultrasonic wave cosmetic device for producing ultrasonic wave stimulation on the facial skin by a vibration unit having an ultrasonic wave vibration element. The ultrasonic wave cosmetic device includes a probe provided with a vibration unit where one surface of the vibration unit contacts the skin and another surface is structured by a horn connected to the ultrasonic wave vibration element, and a drive unit for driving the ultrasonic wave vibration element. The drive unit produces one of either a first fundamental frequency where a half-wave length thereof matches a thickness of the vibration unit, which is a sum of the ultrasonic wave vibration element and the horn, when propagating therethrough, or a first harmonic frequency which is an integer multiple of the first fundamental frequency, as a drive frequency for driving the ultrasonic wave vibration element.

Frequency domain identification of Hammerstein models

Abstract: This paper discusses Hammerstein model identification in frequency domain using the sampled input-output data. By exploring the fundamental frequency and harmonics generated by the unknown nonlinearity, we propose a frequency domain approach and show its convergence for both the linear and nonlinear subsystems in the presence of noise. No a priori knowledge of the structure of the nonlinearity is required and the linear part can be non-parametric.

Determination of material properties by use of third-harmonic generation microscopy.

Abstract: The fundamental features of third-harmonic generation microscopy are examined both theoretically and experimentally, and the technique is applied to the characterization of layered structures. Measurements and model calculations have been performed of the third-harmonic yield generated from homogeneous layers. Model calculations based on the paraxial approximation show good agreement with the experimental results, despite the conditions of high numerical aperture. The method proposed here allows for the determination of (i) the layer’s third-order susceptibility relative to that of the substrate, (ii) its index of refraction at the third-harmonic frequency relative to that at the fundamental frequency, and (iii) its thickness and for the identification of a gradient region between two adjacent layers.

Analytical derivation of a two-section impedance transformer for a frequency and its first harmonic

Abstract: The feasibility of an electrically small two-section transformer (total length one-third-wavelength at the fundamental) capable of achieving ideal impedance matching at a fundamental frequency and its first harmonic is demonstrated, analytically. To achieve this, the exact solution to the resulting transcendental transmission line equations for two sections is obtained with no restrictions. The parameters of the transformer are presented in explicit closed form and are exact. The results of this study are useful for a number of practical design problems, including dual-band antennas and RF circuits in general.

Evidence for two pitch encoding mechanisms using a selective auditory training paradigm.

Abstract: The neural mechanisms underlying the perception of pitch, a sensory attribute of paramount importance in hearing, have been a matter of debate for over a century. A question currently at the heart of the debate is whether the pitch of all harmonic complex tones can be determined by the auditory system’s using a single mechanism, or whether two different neural mechanisms are involved, depending on the stimulus conditions. When the harmonics are widely spaced, as is the case at high fundamental frequencies (F0s), and/or when the frequencies of the harmonics are low, the frequency components of the sound fall in different peripheral auditory channels and are then “resolved” by the peripheral auditory system. In contrast, at lowF0s, or when the harmonics are high in frequency, several harmonics interact within the passbands of the same auditory filters, being thus “unresolved” by the peripheral auditory system. The idea that more than one mechanism mediates the encoding of pitch depending on the resolvability status of the harmonics was investigated here by testing for transfer of learning inF0 discrimination between different stimulus conditions involving either resolved or unresolved harmonics after specific training in one of these conditions. The results, which show some resolvability-specificity ofF0-discrimination learning, support the hypothesis that two different underlying mechanisms mediate the encoding of theF0 of resolved and unresolved harmonics.

Ultrasound imaging system and method based on simultaneous multiple transmit-focusing using weighted orthogonal chirp signals

Abstract: The present invention discloses an ultrasound imaging system and method which make a harmonic image of a good SNR (signal-to-noise ratio) by effectively removing fundamental frequency components through a pulse-compressing using the weighted chirp signals. The ultrasound imaging system includes: a transducer array for converting weighted chirp signals to ultrasound signals, and transmitting the ultrasound signals to a target object; a receiver for receiving signals reflected from the target object; a pulse-compressor for selectively pulse-compressing fundamental frequency components or harmonic frequency components in the reflected signals; and a producer for producing receive-focused signals from the pulse-compressed signals. Therefore, the ultrasound imaging system can form ultrasound image using the fundamental frequency components, and can form ultrasound harmonic image using the harmonic frequency components according to 2fo-correlation method or 2fo-correlation(PI) method.

Characterization of a Compliant-Backplate Helmholtz Resonator for An Electromechanical Acoustic Liner

Abstract: Passive acoustic liners are currently used to reduce the noise radiated from aircraft engine nacelles. This study is the first phase in the development of an actively-tuned electromechanical acoustic liner that potentially offers improved noise suppression over conventional multi-layer liners. The underlying technical concept is based on the idea that the fundamental frequency of a Helmholtz resonator may be adjusted by adding degrees of freedom (DOF) via substitution of a rigid wall with a piezoelectric composite diaphragm coupled to a passive electrical shunt network. In this paper, a Helmholtz resonator containing a compliant aluminum diaphragm is investigated to provide a fundamental understanding of this two DOF system, before adding complexity via the piezoelectric composite material. Using lumped elements, an equivalent circuit model is derived, from which the transfer function and acoustic impedance are obtained. Additionally, a mass ratio is introduced that quantifies the amount of coupling betwe...

Fundamental frequency Gabor filters for object recognition

Abstract: Gabor filters are a widely used feature extraction method in image analysis. In this study, a method is presented that utilises Gabor filters for extracting fundamental frequencies of objects. The fundamental frequencies represent the shape of an object and can be used to classify objects with dissimilar spatial dimensions. Theoretical results are verified by experiments with real images of electronic components. Experiments indicate that the fundamental frequency Gabor filters are a robust tool for rotation and translation invariant object recognition.

An Analytic Method for Measuring Accurate Fundamental Frequency Components

Abstract: This paper proposes an analytic method for measuring the accurate fundamental frequency component of a fault current signal distorted with a DC-offset, a characteristic frequency component, and harmonics. The proposed algorithm is composed of four stages: sine filter, linear filter, Prony's method, and measurement. The sine filter and the linear filter eliminate harmonics and the fundamental frequency component, respectively. Then Prony's method is used to estimate the parameters of the DC-offset and the characteristic frequency component. Finally, the fundamental frequency component is measured by compensating the sine-filtered signal with the estimated parameters. The performance evaluation of the proposed method is presented for a-phase to ground faults on a 345 kV 200 km overhead transmission line. The electromagnetic transient program (EMTP) is used to generate fault current signals under different fault locations and fault inception angles. It is shown that the analytic method accurately measures the fundamental frequency component regardless of the characteristic frequency component as well as the DC-offset.

Multi-level voltage sourced conversion by voltage reinjection at six times the fundamental frequency

Abstract: The proposed multilevel voltage-sourced converter is based on the reinjection of DC voltage pulses at six times the fundamental frequency. The extra (reinjection) components required are justified by a substantial reduction in the capacitor size. It is shown that the resulting voltage and current harmonics are well within the present standards without the assistance of pulse-width modulation. Theoretical waveforms are verified by computer simulation using the PSCAD/EMTDC package.

Nonlinear Vibration of Liquid Droplet by Surface Acoustic Wave Excitation

Abstract: Vibration of a liquid droplet is easily controlled by the Rayleigh surface acoustic wave (SAW). In the vibration of a liquid droplet, two cases are considered: free vibration and forced vibration when it is excited without and with SAW excitation, respectively. For the free vibration, the theoretical and experimental results have already been reported. In the forced vibration, when input excitation was increased, we had determined experimentally that vibration of a liquid droplet shows two nonlinear phenomena. One is, with the increase in SAW input voltage, resonance frequency decreases and vibration amplitude exhibits jump phenomenon. The other, in addition to the fundamental frequency, second and third harmonics, and 1/2 and 3/2 subharmonics are observed. In this report, we explain the two nonlinear phenomena qualitatively using the Duffing equation including the term of a nonlinear spring.

Method and device for attenuating harmonics in semiconductor plasma processing systems

Abstract: A system and method for maintaining a plasma in a plasma region, by supplying RF power at a fundamental frequency to the plasma region together with a gas in order to create an RF electromagnetic field which interacts with the gas to create a plasma that contains electromagnetic energy components at frequencies that are harmonics of the fundamental frequency. The components at frequencies that are harmonics of the fundamental frequency are removed from the plasma by placing a body of an RF absorber material in energy receiving communication with the plasma, the body having a frequency dependent attenuation characteristic such that the body attenuates electrical energy at frequencies higher than the fundamental frequency more strongly than energy at the fundamental frequency.

38 GHz push-push GaAs-HBT MMIC oscillator

Abstract: Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset.