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Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.


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PatentDOI
Toshiaki Fukada1
TL;DR: In this article, a segment pitch pattern model is used to model time change in a fundamental frequency of a phoneme belonging to a predetermined phonemic environment with a polynomial segment model.
Abstract: A speech information processing apparatus and method performs speech recognition. Speech is input, and feature parameters of the input speech are extracted. The feature parameters are recognized based on a segment pitch pattern model. The segment pitch pattern model may be obtained by modeling time change in a fundamental frequency of a phoneme belonging to a predetermined phonemic environment with a polynomial segment model. The segment pitch pattern model may also be obtained by modeling with at least one of a single mixed distribution and a multiple mixed distribution.

36 citations

Journal ArticleDOI
TL;DR: In this paper, a voltage waveform tailoring approach is proposed for the control of the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and the generation of atomic nitrogen as well as helium metastables.
Abstract: Atmospheric pressure capacitively coupled radio frequency discharges operated in He/N2 mixtures and driven by tailored voltage waveforms are investigated experimentally using a COST microplasma reference jet and by means of kinetic simulations as a function of the reactive gas admixture and the number of consecutive harmonics used to drive the plasma. Pulse-type 'peaks'-waveforms, that consist of up to four consecutive harmonics of the fundamental frequency (f = 13.56 MHz), are used at a fixed peak-to-peak voltage of 400 V. Based on an excellent agreement between experimental and simulation results with respect to the DC self-bias and the spatio-temporal electron impact excitation dynamics, we demonstrate that Voltage Waveform Tailoring allows for the control of the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and, thus, the generation of atomic nitrogen as well as helium metastables, which are highly relevant for a variety of technological and biomedical applications. By tuning the number of driving frequencies and the reactive gas admixture, the generation of these important species can be optimised. The behaviour of the DC self-bias, which is different compared to that in low pressure capacitive radio frequency plasmas, is understood based on an analytical model.

36 citations

Journal ArticleDOI
TL;DR: This study reviews for the first time the effects of temperature on acoustic communication in fishes and analyses whether changes in sound properties are coupled to changes in auditory sensitivities, as determined in otophysines, which possess enhanced hearing abilities.
Abstract: Correspondence Friedrich Ladich, Department of Behavioural Biology, University of Vienna, Vienna, Austria. Email: friedrich.ladich@univie.ac.at Abstract Temperature affects peripheral and central mechanisms of signal production and detection in ectothermic animals. This study reviews for the first time the effects of temperature on acoustic communication in fishes and analyses whether changes in sound properties are coupled to changes in auditory sensitivities. Effects of temperature on sound production have been studied in approximately one dozen families of teleosts. Calling activity increased or was unaffected by temperature, in the latter case probably because seasonal, daily and lunar rhythms also influence mating behaviour and calling. Sound characteristics (pulse repetition rate, fundamental frequency) are positively correlated with temperature if pulses are directly based on sonic muscle contractions. In fishes possessing other sonic mechanisms, the dominant frequency of their pulsatile pectoral sounds may increase as well. Auditory sensitivities were mainly determined in otophysines, which possess enhanced hearing abilities. Studies revealed that hearing increased with temperature, in particular at higher frequencies. We know close to nothing about whether temperaturedependent changes in sound characteristics are coupled to changes in auditory sensitivity or mate choice. Female midshipman toadfish appear to choose males based on call frequency, which varies with temperature. Future studies need to address several topics: (i) temperature effects on sound production have to be separated from other sources of variation; (ii) effects on hearing need to be studied in many more taxa; (iii) potential negative effects of global warming on acoustic communication (because of temperature coupling) need to be investigated because fish constitute a major source of protein for humans.

36 citations

Journal ArticleDOI
TL;DR: A comprehensive evaluation of the pitch estimation results shows the superiority of the proposed method over some of the state-of-the-art methods under low levels of SNR.
Abstract: In this paper, a method for the estimation of pitch from noise-corrupted speech observations based on extracting a pitch harmonic and the corresponding harmonic number is proposed. Starting from the harmonic representation of clean speech, a simple yet accurate harmonic sinusoidal autocorrelation (HSAC) model is first derived. By employing this HSAC model expressed in terms of the pitch harmonics of the clean speech, a new autocorrelation-domain least-squares fitting optimization technique is developed to extract a pitch harmonic from the noisy speech. Then, the harmonic number associated with the pitch harmonic is determined by maximizing an objective function formulated as an impulse-train weighted symmetric average magnitude sum function (SAMSF) of the noisy speech. The period of the impulse-train is governed by the estimated pitch harmonic and the maximization of the objective function is carried out through a time-domain matching of periodicity of the impulse-train with that of the SAMSF. An SAMSF-based pitch tracking scheme using dynamic programming is devised to obtain a smoothed pitch contour. In order to demonstrate the efficacy of the proposed method, simulations are conducted by considering naturally spoken speech signals in the presence of white or multi-talker babble noise at different signal-to-noise ratio (SNR) levels. A comprehensive evaluation of the pitch estimation results shows the superiority of the proposed method over some of the state-of-the-art methods under low levels of SNR.

36 citations

Journal ArticleDOI
TL;DR: In this article, the frequency multiplication of a two-stage tapered gyrotron traveling wave tube amplifier is experimentally verified in lowvoltage and low-current operation by modulating an axis-encircling electron beam at the fundamental harmonic cyclotron frequency in the input stage.
Abstract: The frequency multiplication of a two-stage tapered gyrotron traveling wave tube amplifier is experimentally verified in low-voltage and low-current operation. By modulating an axis-encircling electron beam at the fundamental harmonic cyclotron frequency in the input stage, a frequency-tripled signal induced by the third-harmonic component of the modulated beam current is chosen to be extracted from the output stage. Both interaction stages are linearly tapered to improve stability and bandwidth. The third-harmonic frequency multiplication is predicted theoretically and investigated using a self-consistent large-signal theory and a particle-in-cell code simulation, which estimate a pure third-harmonic generation and a power-scaling law. In the experiment, X-band drive signals from 10.6-12 GHz are multiplied by a factor of three to produce Ka-band output frequencies from 31.8-36 GHz, showing reasonable agreement with theoretical predictions for a 30-kV, 160-mA axis-encircling electron beam.

36 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022101
2021236
2020335
2019421
2018375