Showing papers on "Fundamental frequency published in 1999"

Fixed point analysis of frequency to instantaneous frequency mapping for accurate estimation of F0 and periodicity

Abstract: An accurate fundamental frequency (F0) estimation method for non-stationary, speech-like sounds is proposed based on the differential properties of the instantaneous frequencies of two sets of filter outputs. A specific type of fixed points of mapping from the filter center frequency to the output instantaneous frequency provides frequencies of the constituent sinusoidal components of the input signal. When the filter is made from an isometric Gabor function convoluted with a cardinal B-spline basis function, the differential properties at the fixed points provide practical estimates of the carrier-to-noise ratio of the corresponding components. These estimates are used to select the fundamental component and to integrate the F0 information distributed among the other harmonic components.

The Effects of a Flattened Fundamental Frequency on Intelligibility at the Sentence Level

Abstract: The purpose of this preliminary experiment was to evaluate the effect of a flattened fundamental frequency (F0) contour on sentence intelligibility. The perceptual dimension monotone pitch is frequ...

Medical ultrasonic diagnostic imaging method and apparatus

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. The transmitting step includes the step of: applying the plurality of waveforms to a respective plurality of transducer elements, a first waveform of the plurality of waveforms characterized by a first value of a harmonic power ratio, waveforms transmitted from the transducer elements and corresponding to the plurality of waveforms summing as an acoustic waveform substantially at the point, the acoustic waveform characterized by a second value of the harmonic power ratio less than the first value. The imaging method can also include a step for subdividing the transmit aperture into two or more subapertures, each subaperture having at least four adjacent transducer elements. The subapertures are phased differently with respect to one another to selectively reduce either fundamental components or harmonic components of echoes from tissue. These techniques can be used to improve contrast agent harmonic imaging as well as tissue harmonic imaging, depending upon the phase shift selected.

Ultrasonic tissue harmonic imaging

Abstract: An ultrasonic diagnostic imaging system and methods are described which produce tissue harmonic ultrasonic images from harmonic echo components of a transmitted fundamental frequency. Fundamental frequency waves are transmitted by an array transducer to focus at a focal depth. As the transmitted waves penetrate the body, the harmonic effect develops as the wave components begin to focus. The harmonic response from the tissue is detected and displayed, while clutter from the fundamental response is reduced by excluding fundamental frequencies. The technique is especially useful for imaging the endocardial tissue of the heart.

AC and DC bipolar voltage source using quantized pulses

Abstract: We have developed an accurate bipolar voltage source for AC and DC metrology, based on the quantized pulses of Josephson junctions. The output voltage is a factor of 4-6 higher than the amplitude of previous unipolar waveforms; this is achieved by generating bipolar waveforms where arrays of junctions are driven with both a broadband two-level digital code and a sinusoidal frequency. We experimentally demonstrate two bipolar waveforms: a 5 kHz sine wave with /spl plusmn/18 mV peak amplitude and quantization noise power eight orders of magnitude below the power in the fundamental frequency, and a 3.5 kHz square wave with /spl plusmn/13 mV peak amplitude and even harmonics at -100 dB (carrier).

A Comparison of High Precision FO Extraction Algorithms for Sustained Vowels

Abstract: Perturbation analysis of sustained vowel waveforms is used routinely in the clinical evaluation of pathological voices and in monitoring patient progress during treatment. Accurate estimation of voice fundamental frequency (F0) is essential for accurate perturbation analysis. Several algorithms have been proposed for fundamental frequency extraction. To be appropriate for clinical use, a key consideration is that an F0 extraction algorithm be robust to such extraneous factors as the presence of noise and modulations in voice frequency and amplitude that are commonly associated with the voice pathologies under study. This work examines the performance of seven F0 algorithms, based on the average magnitude difference function (AMDF), the input autocorrelation function (AC), the autocorrelation function of the center-clipped signal (ACC), the autocorrelation function of the inverse filtered signal (IFAC), the signal cepstrum (CEP), the Harmonic Product Spectrum (HPS) of the signal, and the waveform matching function (WM) respectively. These algorithms were evaluated using sustained vowel samples collected from normal and pathological subjects. The effect of background noise and of frequency and amplitude modulations on these algorithms was also investigated, using synthetic vowel waveforms.

Effects on nonlinearity on the estimation of in situ values of acoustic output parameters.

Abstract: Water can generate extreme waveform distortion compared to tissue, as indicated by the Gol’dberg number for water, which is 20 times larger than that of tissue at typical diagnostic ultrasound levels. This result was demonstrated by using tofu as a tissue mimicking material. By adjusting transducer voltage drive levels in water to match the peak rarefactional pressures in water to those of waveforms in tofu, a close correspondence was obtained for the peak compressional pressure and time average intensity with depth. A poorer correspondence was found by comparing tofu waveforms with water waveforms that were compensated for broadband attenuation and driven at the same voltage level as tofu. A simplified broadband derating factor, allowing for bandwidth adjustment, was shown to be more accurate than the standard monochromatic derating. Several new indicators for quantifying the degree of observed nonlinearity are suggested: a field based nonlinearity parameter, a peak pressure ratio pc/pr, and a second harmonic to fundamental frequency spectral ratio. These indicators may have the potential for more consistent characterization of nonlinear relationships among output parameters and drive levels. KEY WORDS: Nonlinearity; Attenuation; Ultrasonic exposimetery; Harmonic; Hydrophone.

Planar Schottky diode frequency multiplier for molecular spectroscopy up to 1.3 THz

Abstract: We present a novel and compact frequency multiplier design for broad-band spectroscopy up to 1.38 THz. The multiplier generates harmonics of a fundamental frequency between 110 and 240 GHz. The key element of the multiplier is a newly developed planar Schottky diode. Harmonic power generation is optimized with the aid of three tuning elements. The performance of the multiplier was checked spectroscopically.

Dynamics of the quantized radiation field in a cavity vibrating at the fundamental frequency

Abstract: We present a method to solve exactly a one-dimensional model of quantized radiations in a cavity oscillating in the fundamental resonance, using the effective Hamiltonian derived by C. K. Law [Phys. Rev. A 49, 433 (1994)]. With this method. we derived explicit analytical expressions for the diagonalized Hamiltonian, the time-varying annihilation, creation, and photon number operators for the radiation field, which completely specify the dynamics of the system. [S1050-2947(99)00604-6].

Low complexity frequency estimator and interference cancellation method and device

Abstract: A method and apparatus for estimating the frequency of a periodic signal and for canceling the interference in a modem signal. Power line noise may interfere with electronic signals. Since power lines may be either 50 Hz or 60 Hz, depending on the country, frequency estimation of the periodic power line noise is necessary. Modem signals are received and autocorrelated in order to identify the periodic characteristics of the signal over time. Once the frequency is identified, the power line noise is modeled based on creating a circular buffer. Initially, the circular buffer is composed of scaled samples of one cycle of the fundamental frequency of the power line noise. Thereafter, samples are received, scaled, and combined with previous buffer values in order to update the buffer. In this manner, the buffer models the power line noise, so that the power line noise may be removed from the system.

Medical diagnostic ultrasound method and system for contrast specific frequency imaging

Abstract: A medical diagnostic ultrasound imaging method and system insonify a tissue containing a contrast agent with ultrasonic transmit signals at a fundamental frequency f. Backscattered ultrasonic receive signals are acquired and filtered to emphasize frequency components between the fundamental frequency f and the second harmonic frequency 2 f, and the filtered receive signals are processed for display. This filtering enhances the ability of the method and system to discriminate between contrast agent and adjacent tissue.

Fourth harmonic generation apparatus

Abstract: A fourth harmonic frequency generating method and apparatus is provided The system includes within the optical cavity an active laser medium (LM), a second harmonic generator for generating second harmonic frequency of the fundamental frequency emitted by the laser The fundamental beam is directed to a second harmonic generation crystal (NLC1) where a portion of the fundamental beam is converted to a second harmonic beam Both the second harmonic and unconverted fundamental beams are directed back across the second harmonic generator by reflective surfaces for a second pass prior to any conversion of second harmonic beam to a higher harmonic beam Preferably the second harmonic and fundamental beams are reflected by one of the laser cavity reflective surfaces for the second pass Optionally, there can be separate reflective surfaces to reflect each of the fundamental and second harmonic beams A third harmonic generator (NLC2) for generating third harmonic frequency of the fundamental frequency, a fourth harmonic generator (NLC3) for generating a fourth harmonic frequency of the fundamental frequency and a wavelength selective coupling (MD) to facilitate the removal of the fourth harmonic beam from the optical cavity are provided in optical communication with the reflected second harmonic and fundamental beam Optionally the unconverted second harmonic beam can be directed through the laser medium as additional pumping Optionally substantially all UV beams are removed from the laser cavity The resulting laser has improved conversion efficiency and an improved mode quality

Mechanical behavior and sound generation efficiency of prestressed, elastically clamped and thermomechanically driven thin film sandwiches

Abstract: A model of thermomechanically driven plates as used, e.g., for acoustic microresonators is reported. The model describes the quasibuckling, excitation, fundamental frequency and vibration mode of multilayered plates under plane strain. The plates consist of stacked thin films with individual elastic modulus, Poisson's ratio, prestress, heat capacity and coefficient of thermal expansion. Membrane edges are elastically clamped to lateral supports. In thin plates two driving mechanisms are identified: the first couples the thermomechanical bending moment to the curvature of the vibration mode; the second couples the thermomechanical line stress to the periodic length change of the vibrating quasibuckled structure. Results of the model include vibration amplitude, sound field pressure, emitted power and quality factor as functions of the membrane properties. Maximum output is obtained close to the quasibuckling transition of the structures, where their resonance frequency is minimum. Largest sound pressures are generated by structures with rigid supports or with vanishing initial bending moment. The model shows excellent agreement with experimental data from micromachined resonant silicon membranes.

Surface acoustic wave harmonic analysis

Abstract: A method for sensing and analyzing data with surface acoustic wave (SAW) devices comprises the steps of: propagating a sampling signal at a fundamental frequency through a SAW device (12) coated for selective adsorption; measuring at least one parameter of at least one higher order harmonic of the fundamental frequency sampling signal; exposing the coated SAW device (12) to enable the selective adsorption; measuring the at least one higher order harmonic of the fundamental frequency sampling signal after the exposing step; comparing the measurements of the at least one parameter of the at least one higher order harmonic before and after the exposing step; and, deriving a result of the selective adsorption based upon the comparing step. The at least one parameter is harmonic power and harmonic frequency. The at least one higher order harmonic is one or more odd harmonics.

Context dependence of fundamental-frequency discrimination: lateralized temporal fringes.

Abstract: In a two-interval, two-alternative, forced-choice (2I-2AFC) adaptive procedure, listeners discriminated between the fundamental frequencies (F0s) of two 100-ms harmonic target complexes. This ability can be impaired substantially by the presence of another complex (the “fringe”) immediately before and after each target complex. It has been shown that for the impairment to occur (i) target and fringes have to be in the same frequency region; (ii) if all harmonics of target and fringes are unresolved then they may differ in F0; otherwise, they have to be similar [C. Micheyl and R. P. Carlyon, J. Acoust. Soc. Am. 104, 3006–3018 (1998)]. These findings have been discussed in terms of information about the fringe’s F0 being included in the estimate of the F0 of the target, and in terms of auditory streaming. The present study investigated the role of perceived location and ipsilateral versus contralateral presentation of the fringes on F0 discrimination of the target. Experiment 1 used interaural level differe...

Multiple voice tracking system and method

Abstract: For tracking multiple, simultaneous voices, predicted tracking is used to follow individual voices through time, even when the voices are very similar in fundamental frequency. An acoustic waveform comprised of a group of voices is submitted to a frequency estimator, which may employ an average magnitude difference function (AMDF) calculation to determine the voice fundamental frequencies that are present for each voice. These frequency estimates are then used as input values to a recurrent neural network that tracks each of the frequencies by predicting the current fundamental frequency value for each voice present based on past fundamental frequency values in order to disambiguate any fundamental frequency trajectories that may be converging in frequency.

Medical diagnostic ultrasound imaging system and method with fractional harmonic seed signal

Abstract: Medical diagnostic ultrasonic imaging systems and methods image at a fractional harmonic such as f 0 /2 or 3f 0 /2, where f 0 is the fundamental frequency of the associated transmit beam. In order to improve fractional harmonic imaging, the transmit beam includes a fractional harmonic seed component, which may also have a center frequency of f 0 /2 or 3f 0 /2. Multiple pulse imaging methods using transmit beams having such fractional harmonic seed components further enhance fractional harmonic imaging.

Signal representation and estimation of spectral parameters by inharmonic comb filters with application to the piano

Abstract: A method for signal representation in the frequency domain is described, using a comb filter design with nonequidistant spacing of the filter bands (inharmonic comb filter). This approach offers several advantages when studying the properties of a signal source with inharmonic components. An analytical relation between the partial frequencies, or some hypothesis of this relation, is needed beforehand. An application of the method is presented in which piano tones are visualized in a new way, allowing for an automatic and accurate measurement of fundamental frequency and inharmonicity coefficient. Possible directions for further development and some interesting application areas are discussed.

Integrating pitch and LPC-residual information with LPC-cepstrum for text-independent speaker recognition

Abstract: In the speaker recognition, when the cepstral coefficients are calculated from the LPC analysis parameters, the prediction error, or LPC residual signal, is usually ignored. However, there is an evidence that it contains a speaker specific information. The fundamental frequency of the speech signal or the pitch, which is usually extracted from the LPC residual, has been used for speaker recognition purposes, but because of the high intraspeaker variability of the pitch it is also often ignored. This paper describes our approach to integrating the pitch and LPC-residual with the LPC-cepstrum in a Gaussian Mixture Model (GMM) based speaker recognition system. The pitch and/or LPC-residual are considered as an additional features to the main LPC derived cepstral coefficients and are represented as a logarithm of the F0 and as a filter bank mel frequency cepstral (MFCC) vector respectively. The second task of this research was to verify whether the correlation between the different information sources is useful for the speaker recognition task. For the experiments we used the NTT database consisting of high quality speech samples. The speaker recognition system was evaluated in three modes-integrating only pitch or only LPC-residual and integrating both of them. The results showed that adding the pitch gives significant improvement only when the correlation between the pitch and cepstral coefficients is used. Adding only LPC-residual also gives significant improvement, but in contrast to the pitch, using the correlation with the cepstral coefficients does not have big effect. The best results we achieved using both the pitch and LPC-residual and are 98.5% speaker identification rate and 0.21% speaker verification equal error rate compared to 97.0% and 1.07% of the baseline system respectively.

Electronic music system for detecting pitch

Abstract: A method for detecting the pitch of a musical signal comprising the steps of receiving the musical signal, identifying an active portion of the musical signal, identifying a periodic portion of the active portion of the musical signal, and determining a fundamental frequency of the periodic portion of the musical signal.