Showing papers on "Fundamental frequency published in 1975"
TL;DR: In this article, the process of internal gravity wave generation by the simple harmonic flow (U = U0, cos ω0t) of a stably stratified fluid over an obstacle is investigated in some detail.
Abstract: The process of internal gravity wave generation by the simple harmonic flow (U = U0, cos ω0t) of a stably stratified fluid (Brunt–Vaisala frequency N) over an obstacle is investigated in some detail. Attention is primarily directed to the behaviour of the solution in various limiting cases, and to estimating the flux of energy into the internal wave field. In general, waves are generated not only at the fundamental frequency ω0, but also at all of its harmonics. But, for values of ω0/N greater than about one half, the waves of fundamental frequency are dominant. For values of ω0/N, less than about one half, the quasi-static approximation, in which the problem is considered as a slowly-varying version of the classical lee wave problem, is found to provide a viable estimate for the wave field. The general solution is found to compare favourably with the limited available experimental data.
275 citations
TL;DR: In this paper, a partly experimental approach to the complex relationship that exists between the abstract, global structures of intonation, and the concrete, atomistic features of the course of the fundamental frequency is presented.
140 citations
TL;DR: In this article, the magnitude of sampling errors associated with estimates of the mean, median, and standard deviation of voice fundamental frequencies (fo) during oral readin' was investigated.
Abstract: Two experiments are reported in which the magnitude of sampling errors associated with estimates of the mean, median, and standard deviation of voice fundamental frequencies (fo) during oral readin...
88 citations
TL;DR: An algorithm that determines the fundamental frequency of sampled speech by segmenting the signal into pitch periods, which processes both male and female speech, provides a voiced-unvoiced decision, and operates in real time on a medium speed, general purpose computer.
Abstract: This paper presents an algorithm that determines the fundamental frequency of sampled speech by segmenting the signal into pitch periods. Segmentation is achieved by identifying those samples of the waveform corresponding to the beginning of each pitch period. The segmentation is accomplished in three phases. First, using zero crossing and energy measurements, a data structure is constructed from the speech samples. This structure contains candidates for pitch period markers. Next, the number of candidate markers within this structure is reduced utilizing syllabic segmentation, coarse pitch frequency estimations, and discrimination functions. Finally, the remaining pitch period markers are corrected, compensating for errors introduced by the data reduction process. This algorithm processes both male and female speech, provides a voiced-unvoiced decision, and operates in real time on a medium speed, general purpose computer.
56 citations
01 Nov 1975
TL;DR: In this article, the fundamental system impedance as seen from the relaying point is used as the basis for the decision to give the trip signal, which can be calculated from knowledge of the fundamental frequency components of the voltage and current waveforms, in turn, being determined by processing appropriate waveforms sampled at the relay point.
Abstract: For distance-relay applications, the fundamental system impedance as seen from the relaying point is used as the basis for the decision to give the trip signal. This system impedance can be calculated from knowledge of the fundamental frequency components of the voltage and current waveforms, these, in turn, being determined by processing appropriate waveforms sampled at the relay point. Fourier-series analysis is one method suitable for processing the sampled waveforms and for determining their fundamental components. The analysis is designed for continuous, periodic waveforms and, in these circumstances, separates the various harmonic components of the waveform. Its behaviour under the nonperiodic conditions of fault incidence and transient interference will be demonstrated.
47 citations
TL;DR: In this article, the fundamental frequency of vibration of a thin elastic plate elastically restrained against rotation along the boundary and subjected to a hydrostatic state of in-plane stress was determined.
46 citations
Patent•
14 Jan 1975
TL;DR: In this article, the presence of an active magnetic marker in the alternating magnetic field is detected by detecting a predetermined even harmonic of the fundamental frequency, which is then detected by demagnetizing the control element of the marker associated with an article authorized for removal from the protected area to permit that article to pass through the magnetic field undetected.
Abstract: In a pilferage detection system employing apparatus for generating a magnetic field of alternating polarity and predetermined fundamental frequency through which articles subject to pilferage must pass to leave a protected area and a magnetic marker associated with each article in the protected area, markers are provided which generate both odd and even harmonics of the fundamental frequency in response to the alternating magnetic field when the marker is active (i.e., a control element of the marker is magnetized) and which generate only odd harmonics of the fundamental frequency when the marker is inactive. The presence of an active marker in the alternating magnetic field is therefore detected by detecting a predetermined even harmonic of the fundamental frequency. Apparatus is also provided for demagnetizing the control element of the marker associated with an article authorized for removal from the protected area to permit that article to pass through the alternating magnetic field undetected.
40 citations
TL;DR: This experiment in aural speaker identification attempts to ascertain the relative contributions of fundamental frequency and formant frequencies in speech samples.
Abstract: This experiment in aural speaker identification attempts to ascertain the relative contributions of fundamental frequency and formant frequencies. Speech samples were four voiced, whispered, and low-p
32 citations
TL;DR: In this article, the free extensional (in plane) vibration of thin plates of Hookean material of various shapes was studied, and solutions for dilatational and rotational vibrations were obtained separately.
Abstract: The problem of free extensional (in plane) vibration of thin plates of Hookean material of various shapes was studied. Solutions for dilatational and rotational vibrations were obtained separately. The boundary conditions were satisfied in a least‐square sense. Numerical computations were performed for circular, elliptical, triangular, square, and hexagonal plates. The nodal pattern corresponding to each natural frequency for different modes was obtained. The frequency parameters computed for the circular plate are found to be within 0.05% of published results. For plates where known results were not available, the accuracy was checked by taking additional terms in the series solution and by dividing the boundary perimeter into finer intervals. It was found that the circular plate had the lowest fundamental frequency (k1) at 2.049. The value increases as the shape is changed from a circle, with the triangular plate having the highest value at 6.733 in dilatational vibration while the frequencies in rotati...
27 citations
01 Jan 1975
TL;DR: In this paper, the authors studied how dogs discriminate synthesized speech-like sounds that are perceived by man as vowels and found the features which may be used as cues for the discrimination.
Abstract: In the present research we have studied how animals (dogs) discriminate synthesized speech-like sounds that are perceived by man as vowels [a] and [i]. By varying signal parameters (the fundamental frequency, intensity, duration and the number of formants) we tried to find the features which may be used as cues for the discrimination.
25 citations
TL;DR: In this paper, an approximate formula for the fundamental frequency of thin elastic plates is presented, and the degree of accuracy of this approximation is compared with values computed by more exact analysis for several different plates with combinations of clamped and simply supported boundary conditions.
Patent•
02 Jun 1975
TL;DR: In this article, an electronic musical instrument of the keyboard type used to electronically reproduce piano sounds is described, where means are provided for producing a fundamental square wave frequency and the second and fourth harmonics thereof, in response to the actuation of a given key on the keyboard.
Abstract: The embodiment of the invention disclosed herein is directed to an electronic musical instrument of the keyboard type used to electronically reproduce piano sounds. The circuit has means to vary the amplitude of the piano voice in response to the velocity of the downward movement of the key. Means are provided for producing a fundamental square wave frequency and the second and fourth harmonics thereof, in response to the actuation of a given key on the keyboard. One circuit arrangement includes means for combining the fundamental frequency and the second and fourth harmonics in a predetermined time relation to produce the zero, attack, peak, and decay characteristics of a piano voice as actually produced by a piano string. Amplitude limiting means are coupled to the circuit for controlling the amplitude of the harmonics in response to predetermined values so that mixing of the fundamental frequency and the second and fourth harmonics along predetermined points of the piano voice characteristics curve will more accurately reproduce electronically the sounds of a piano. Another circuit arrangement provides means for rapid recovery of the piano circuit so that the keys can be actuated in rapid succession.
TL;DR: In this paper, the authors considered a closed tube driven at one-half of the fundamental frequency and showed that the theory of Chester breaks down in the inviscid case at a sufficient intensity of a first resonant overtone.
Abstract: A closed tube is considered driven at one-half of the fundamental frequency. The interesting fact appears that acoustic theory breaks down in the inviscid case. At a sufficient intensity of a first resonant overtone, the theory of Chester applies.
TL;DR: In this article, the infrared spectrum of HC 13 F 3 was reported for the first time and rotational analysis of several of the fundamental and combination bands were given, including Coriolis x - y and Fermi perturbations.
TL;DR: In this article, the minimum cross-section of a vibrating beam is controlled by the introduction of an inequality constraint, and a finite element displacement formulation is then used in an iterativve manner to arrive at the optimum fundamental frequency and the corresponding material distribution for the discretized beam models with various boundary conditions.
Abstract: Accounting for shear deformations and rotary inertia effects, necessary condition for optimum fundamental frequency of a vibrating beam of constant volume and with a given distribution of non-structural mass, is obtained through the calculus of variations. Minimum cross-section of the beam is controlled by the introduction of an inequality constraint. A finite element displacement formulation is then used in an iterativve manner to arrive at the optimum fundamental frequency and the corresponding material distribution for the discretized beam models with various boundary conditions. A comparison is then made with the corresponding results of an Euler beam.
TL;DR: In this article, the combined effects of amplitude and phase variations on the irradiance in the image of a sinusoidal complex object are investigated for a partially coherent optical system, which is defined as the ratio of the coefficient of a harmonic component to the background.
Abstract: Combined effects of amplitude and phase variations on the irradiance in the image of a sinusoidal complex object are investigated for a partially coherent optical system. For this purpose, the general expression for the irradiance in the image of a sinusoidal complex object that has amplitude transmittance (C + A cos2πx0u) and phase distribution of the form exp(B cos2πx0u) is formulated for a partially coherent optical system. The image irradiance obtained in such an optical system consists of the fundamental frequency and a number of harmonics produced by the nonlinear modulation of the object. The characteristics of the image are assessed in terms of the image contrast, which is defined as the ratio of the coefficient of a harmonic component to the background. By use of the general formula, the image contrast of the fundamental and harmonic components up to sixth order can be calculated for the partially coherent optical system illuminated with bounded and annular illuminations. The typical nonlinear effect occurs in the low-spatial-frequency region. Especially, maxima of the contrast curves occur in the low-frequency region; they may be caused by nonlinearity of the system and effects of phase variations. Analysis and computation showed that, in image formation in a partially coherent optical system, phase variation in the object is extremely influential for the appearance of the image and its contrast.
Patent•
18 Sep 1975
TL;DR: In this article, a set of waveforms are stored in the form of digitalized values of their amplitude at several discrete scanning points, one for each stop on the organ, and the harmonics of the note are in accordance with the waveform selected by the stop.
Abstract: The computerised organ includes a data store which contains a set of waveforms, one for each stop on the organ. Each waveform is stored in the form of digitalised values of its amplitude at several discrete scanning points. When a keyboard switch is actuated, a signal is selected at such a speed that, after conversion to an analogue signal, the corresponding sound signal has the same fundamental frequency as the sound associated with the actuated keyboard switch. The harmonics of the note are in accordance with the waveform selected by the stop. A summing circuit may be used so that several stops on the organ may be used at once.
Patent•
20 Aug 1975
TL;DR: In this paper, a system for time compression and expansion of audio signals comprises a filter for filtering the fundamental frequency component of an input signal reproduced at a speed differing from that at the time of recording, first and second memory devices for carrying out writing in or memorizing and reading out at speeds in accordance with the frequency of applied clock pulses.
Abstract: A system for time compression and expansion of audio signals comprises a filter for filtering the fundamental frequency component of an input signal reproduced at a speed differing from that at the time of recording, first and second memory devices for carrying out writing in or memorizing and reading out at speeds in accordance with the frequency of applied clock pulses, a control signal forming circuit for forming gate control signals and clock pulse signals of different frequency from the output fundamental frequency component of the filter in synchronism with the pitch period thereof, and gates controlled by the gate control signals to pass or not pass the output signals of the first and second memory devices. A time compressed or expanded signal synchronized with the pitch period of the fundamental frequency component of the input signal is led out through these gates.
TL;DR: In this paper, a frequency-domain analysis of the mode-locked intracavity frequency-doubled laser is pursued, and an expression for pulsewidth is derived based upon basic laser parameters and the nonlinear coupling of the frequency doubler.
Abstract: A frequency-domain analysis of the mode-locked intracavity frequency-doubled laser is pursued. An expression for pulse-width is derived based upon basic laser parameters and the nonlinear coupling of the frequency doubler. It is found that mode locking induces an additional loss to the cavity even in the ideal case, so that the frequency-doubled output power at optimum coupling is less than an optimally coupled fundamental frequency laser with identical losses.
TL;DR: In this article, an algorithm is proposed for extracting the pitch of voiced speech based on approximating a given segment of the speech waveform in a least-squares sense by a finite Fourier series.
Abstract: An algorithm is proposed for extracting the pitch of voiced speech. The method is based on approximating a given segment of the speech waveform in a least-squares sense by a finite Fourier series. In the approximation the fundamental frequency of the Fourier series, as well as its coefficients, is considered variable.
TL;DR: In this article, the performance of water filled acousto-optic cells is quantified with particular reference to their use for laser-Doppler anemometry, and the influence of the incident angle and the performance at frequencies close to but different from the fundamental frequency are quantified.
Abstract: The performance of water filled acousto-optic cells is quantified with particular reference to their use for laser-Doppler anemometry. With the cell operating at a frequency of 9.2 MHz, the intensities of the +1 and -1 order beams are shown to account for 76% of the transmitted light intensity for an electrical power input of 0.56W. The influence of the incident angle and the performance of a cell at frequencies close to but different from the fundamental frequency are quantified. Operation of the cells at a frequency of 30 MHz, i.e. close to a third harmonic, is shown to require significantly greater electrical power input but can without introducing thermal connection effects, allow the transmission of a first and zero order beams with equal intensities and a total loss of 8% of the incident intensity. To show that an acousto-optic cell can be used as a beam splitter and frequency shifter, measurements of three components of velocity are reported in the region of recirculation immediately downstream of the centre disc of an annular jet.
TL;DR: In this paper, a theory of steady-state single-frequency second-harmonic generation in a resonator is developed for the case when an active medium and a nonlinear crystal located inside the pump-laser resonator are separated by a beam splitter which deflects the harmonic out of the resonator.
Abstract: A theory of steady-state single-frequency second-harmonic generation in a resonator is developed for the case when an active medium and a nonlinear crystal located inside the pump-laser resonator are separated by a beam splitter which deflects the harmonic out of the resonator. No assumptions are made about the nature of the influence of the harmonic on the the generation of the pump (fundamental-frequency) radiation and the fields in the resonator are defined as superpositions of plane monochromatic waves traveling in opposite directions along the resonator axis. The case of a pump-laser resonator which does not transmit at the fundamental frequency is analyzed in detail. Moreover, a detailed discussion is given of the influence of the absorption in the nonlinear crystal, ratio of the pump and harmonic intensities in the case of their simultaneous generation at the exit from the resonator, influence of feedback at the harmonic frequency (introduced by an additional resonator tuned to the harmonic frequency and coupled optically to the pump-laser resonator), etc. A report is given of an experimental investigation of the dependence of the harmonic intensity on the thickness of the nonlinear crystal and of the influence of a feedback at the harmonic frequency. The experimental results are in good agreement with the theoretical predictions.
TL;DR: An algorithm for the extraction of fundamental frequency (pitch) from digitized speech is described, which operates in the frequency domain using autocorrelation spectra and is optimized for computational efficiency.
Abstract: An algorithm for the extraction of fundamental frequency (pitch) from digitized speech is described. The computer algorithm operates in the frequency domain using autocorrelation spectra and is optimized for computational efficiency. Three basic operations are performed: (1) the digitized speech is low‐pass filtered and down‐sampled to a rate of 2000 samples per second, thereby eliminating frequencies outside the range of possible fundamentals and reducing the quantity of data to be processed. (2) Autocorrelation spectra are computed every 10 msec and pitch values are extracted. (3) The values of fundamental frequency obtained above are edited to eliminate anomalies. Reliability in terms of making the correct voiced/unvoiced decision exceeds 99%, and the program runs in about 14 times real time on a 16‐bit minicomputer.
Journal Article•
TL;DR: Conclusions of the study indicate that fundamental frequency analysis is a valuable supplemental method for objective voice examination.
Abstract: The applicability of a newly developed fundamental frequency analyzer to diagnosis in phoniatrics is reviewed. During routine voice examination, the analyzer allows a quick and accurate measurement of fundamental frequency and sound level of the speaking voice, and of vocal range and maximum phonation time. By computing fundamental frequency histograms, the median fundamental frequency and the total pitch range can be better determined and compared. Objective studies of certain technical faculties of the singing voice, which usually are estimated subjectively by the speech therapist, may now be done by means of this analyzer. Several examples demonstrate the differences between correct and incorrect phonation. These studies compare the pitch perturbations during the crescendo and decrescendo of a swell-tone, and show typical traces of staccato, thrill and yodel. Conclusions of the study indicate that fundamental frequency analysis is a valuable supplemental method for objective voice examination.
TL;DR: In this paper, the problem of optimizing the frequencies of an elastic plate vibrating in an ideal fluid is investigated, and an integro-differential equation describing one-dimensional plate vibrations in a fluid is derived.
Patent•
18 Mar 1975TL;DR: In this article, the linearity of a sweep frequency generator is improved by generating a plurality of harmonics of a fundamental frequency, such harmonics being equally spaced apart in frequency, detecting the coincidences of the output frequency of the sweep generator with the individual frequencies of the various harmonics, generating a train of pulses in response to such coincidences.
Abstract: The linearity of a sweep frequency generator is improved by generating a plurality of harmonics of a fundamental frequency, such harmonics being equally spaced apart in frequency, detecting the coincidences of the output frequency of the sweep generator with the individual frequencies of the various harmonics, generating a train of pulses in response to such coincidences, and controlling the frequency of the sweep frequency generator with a control voltage derived from the pulse train.