Showing papers on "Fundamental frequency published in 1977"

A pitch extraction algorithm based on LPC inverse filtering and AMDF

Abstract: We present an efficient algorithm for determining fundamental frequency and voiced/unvoiced (V/UV) decision of speech. The pitch extractor utilizes the cross-correlation average magnitude difference function (AMDF) waveform that is obtained from the linear prediction residual signal. The decision logic used in pitch extraction is simple and reliable. The periodicity and null depth of AMDF waveforms, together with the average residual energy and the past pitch information, are used in the decision logic for fundamental frequency and V/UV decision. Computer simulation of the algorithm yielded accurate results, even for difficult phonemes for pitch extraction.

Pseudo-maximum-likelihood speech pitch extraction

Abstract: The pitch of a voiced speech segment may be estimated by minimizing the squared error in approximating the segment by the repeated weighted average of successive assumed pitch periods, after a "maximum-likelihood" solution originally due to Slepian. A modification is proposed which allows use of an arbitrary window function and corrects two faults of the "likelihood" function noted by Noll: a linear baseline rise and ambiguous identification of the proper peak. Computationally, the entire formulation is in the time domain. Results are presented for speech both before and after bandpass filtering to simulate telephone transmission. Comparison of these two cases implies that the algorithm is effective for speech in which the fundamental frequency itself is missing.

Acoustic Bulk Wave Resonators and Filters Operating in the Fundamental Mode at Frequencies Greater Than 100 MHz

Abstract: A localised ion-beam milling has been used to increase the fundamental frequency of acoustic-bulk-wave resonators. Monolithic filters in lithium niobate (Y+37°) and lithium tantalate (X) operating, respectively, at 220 and 230 MHz have been realised. The relative bandwidth is equal to 1% and the insertion loss is about 4 dB. An a.t.-cut quartz resonator working in the fundamental mode at 270 MHz with a Q-factor of 12 000 has also been obtained. In this case, the vibrating membrane is 6 μm thick, with a centre portion of diameter 2.5 mm.

Open-loop electric drive with corrective controller

Abstract: A controller minimizes periodic torque or force perturbations in an inductor-type synchronous motor drive by supplying current waveforms to each motor phase that contain a fundamental frequency component and selected harmonic components. The harmonic components in the phase currents heterodyne with the periodic permanent magnet flux fundamental frequency to create periodic torques or forces which subtract from the unwanted torques or forces perturbing the moving portion of the motor. The controller, which includes an interpolator, a memory, and a converter, provides for smooth incremental movement of a member such as a plot head, at substantially constant velocity, by applying selected continuous periodic waveform signals as phase currents to the windings of inductor-type synchronous motors.

Electronic music sampling techniques

Abstract: The disclosure describes improved apparatus for sampling a digitally-stored waveshape only at a rate 2N times the fundamental frequency of a note synthesized, where N is an integer The apparatus includes a digital memory for storing a digital representation of the waveshape A top octave synthesizer produces clock pulses at a rate 2N times the fundamental frequency of a desired note An octave oscillator generates addresses for the digital memory in response to at least some of the clock pulses depending on the octave in which the desired note is located A digital-to-analog converter converts the output from the digital memory into an analog signal suitable for sound production

Optimized mode-locked, frequency doubled laser

Abstract: In a solid state, folded cavity, laser having a fundamental frequency and a second harmonic frequency, the efficiency of the laser is improved by placing a quarter wave plate, at the lower frequency, in the leg of the cavity containing the lasing element and positioning the quarter wave plate by angular rotation to compensate for any polarization discrimination to the laser rod gain.

Electrical apparatus for determining the pitch or fundamental frequency of a musical note

Abstract: An electrical apparatus for determining the fundamental frequency of a musical note wherein the apparatus comprises a plurality of means for generating and responding to pulse type signals. More particularly, first and second means responsive to an electrical representation of the musical note are provided for generating first and second pulse trains whose pulses corresponding to the maxima and minima, respectively, of the electrical representation. The aforesaid first pulse train is applied to a first input of a first logic circuit means whose second input is fed a further pulse train from the output of a second logic circuit means. The second logic circuit means provides at its output either the second pulse train or a pulse train whose pulses are delayed relative to the pulses of the pulse train at the output of the first logic circuit means. In particular, during the initial stages of the electrical representation, the second logic circuit means is controlled to couple the former pulse train to its output and, thereafter, the latter pulse train. With the logic circuit means so controlled and with the first logic circuit means designed to provide an output pulse only for successively occurring pulses at its first and second inputs, respectively, the output pulse train of the first logic circuit means will have a fundamental frequency which accurately portrays that of the electrical representation and, hence, the musical note represented thereby.

An Optimal Control Approach to Minimum-Weight Vibrating Beam Design

Abstract: A gradient projection algorithm is applied to a class of vibrating cantilever beam optimization problems which are formulated as optimal control problems The cross-section area is distributed along the beam for minimum total weight subject to fixed natural frequency constraints and a minimum allowed area limit Three topics receive major emphasis: the effects of shear deformation and rotary inertia, higher-mode frequency constraints, and multiple frequency constraints Computational results are presented for the cases of fixed fundamental frequency, fixed second-mode frequency, and fixed fundamental and second-mode frequencies under a variety of conditions

Frequency measuring apparatus

Abstract: A frequency measuring apparatus is disclosed wherein a plurality of sets of harmonic signals is mixed with a received signal to produce a plurality of groups of beat frequency signals. A plurality of filters, each one being fed by a corresponding one of the groups of beat frequency signals, is provided to reject the beat frequency signals in such group having frequencies greater than one-half the fundamental frequency of the set of signals producing the group of beat frequency signals fed to such one of the filters. A plurality of counters, each one coupled to the output of a corresponding one of the filters, converts the frequency of the beat frequency signals fed to such counter to corresponding digital words. A logic network is provided to calculate the frequency of the received signal from the digital words provided by the counter.

Increase of the first natural frequency and buckling load of plates by optimal fields of initial stresses

Abstract: Departing from the common way of optimization of vibrating structures by an optimal mass distribution this paper deals with the problem of maximizing the fundamental frequency of structures by optimizing fields of initial stresses without varying the given appropriate shape of the structure. Thin elastic circular and rectangular plates are considered, which may be loaded by external inplane forces, and optimal initial membrane stress fields are calculated, which produce values of the first natural frequency of the free bending vibrations as high as possible. As a constraint, the strain energy caused by the field of initial stresses in the resting, externally unloaded plate is given. The computation leads to a max-min-problem solved numerically with the help of gradient methods. The optimal fields of initial stresses of the buckling plates are calculated as extreme cases in the same manner.

Crystal overtone oscillator using cascade connected transistors

Abstract: An overtone oscillator of the feedback type is provided by a transistor, a crystal resonant at a fundamental frequency and higher odd overtone frequencies, and a feedback circuit that includes the crystal, a second transistor connected in cascade with the first transistor and an RC network. This feedback circuit provides the correct phase shift to achieve and sustain oscillations at the desired overtone frequency.

Subharmonic non-linear acoustic resonances in open tubes—Part I, theory

Abstract: An open 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 resonant overtone, the distortion effects become too strong to use an expansion scheme

Computer recognition of linguistic stress patterns in connected speech

Abstract: This paper presents an automatic method which estimates the magnitude of syllable stress in continuous speech using a composite of three acoustic parameters: fundamental frequency, intensity, and duration. Results show that fundamental frequency is the most prominent cue of stress, followed by intensity and vowel duration. Estimations of stress magnitudes based on these three cues are shown to yield stable values in spite of differences in the vowels used, in speakers, and in syllable positions.

Parametric generation of infrared picosecond pulses in LiNbO3 crystals

Abstract: Efficient parametric generation of infrared radiation in LiNbO3 crystals was obtained when these crystals were pumped with the fundamental frequency and second harmonic of a YAG:Nd3+ picosecond laser (the pulse repetition frequency was up to 25 Hz). The maximum energy efficiency of conversion was 17% (the energy of the parametric signal in the 2 μ range was 9×10–4 J) and continuous frequency tuning was obtained in the 1365–4825 and 660–2700 nm ranges (for the fundamental frequency and second harmonic, respectively). The possibility of narrowing the width of the output spectrum by the use of a twocrystal system were considered.

Helix type travelling-wave tube amplifier

Abstract: A band-rejection filter which rejects harmonic components of the fundamental frequency of the output of a helix type travelling-wave tube is built into the connection of the output connection from the tube to its external circuit. A wide variety of specific filter structures are disclosed.

Reduced-cross talk telemetry system and method of manufacture thereof

Abstract: Method and apparatus for providing a multi-channel telemetry system in which the fundamental frequencies of the transmit-receive channels of the system are selected from a series of tentative fundamental frequencies. The successive fundamental frequencies in series therewith each having the same geometric relation to the immediately preceding and immediately succeeding fundamental frequency such that potentially interfering cross talking channels in similar geometric relation may be identified and eliminated.

Acoustic-bulk-wave resonators and filters operating in the fundamental mode at frequencies greater than 100 MHz

Abstract: A localised ion-beam milling has been used to increase the fundamental frequency of acoustic-bulk-wave resonators. Monolithic filters in lithium niobate (Y+37°) and lithium tantalate (X) operating, respectively, at 220 and 230 MHz have been realised. The relative bandwidth is equal to 1% and the insertion loss is about 4 dB. An a.t.-cut quartz resonator working in the fundamental mode at 270 MHz with a Q-factor of 12 000 has also been obtained. In this case, the vibrating membrane is 6 μm thick, with a centre portion of diameter 2.5 mm.

Symmetrical phase shifting apparatus, digital delaying device used therein and harmonic neutralized inverter system using the apparatus

Abstract: A voltage controlled AC static power supply of the harmonic neutralization type uses symmetrical digital phase shifting in order to reconstruct, with pulses of variable width and predetermined different magnitudes generated by inverters, a sinusoidal wave of fundamental frequency. Phase-shifts are obtained digitally from a single pair of frequency signals. Variable length delay lines are used consisting of random-access-memory (RAM) devices in which a selected shift between read and write addresses establishes the desired amount of delay.

Resonator for a musical tone synthesizer

Abstract: A tone synthesizer in which a musical tone of selected fundamental frequency is generated with a resonance effect at selected harmonics of the tone. The resonance effect is produced by adding an amplitude modulated carrier signal to the musical tone, the carrier signal being modulated by a signal having the fundamental frequency of the musical tone and the carrier frequency being an integral multiple of the fundamental.

Apparatus for extracting the fundamental frequency from a complex audio wave form

Abstract: Apparatus for extracting the fundamental frequency from a complex audio wave form and for producing a pulse representation of said fundamental frequency includes a low pass filter having a frequency response characteristic which tends to exclude harmonics together with a control circuit including amplifier means, peak detector means and voltage to current converter means for supplying a control signal to the low pass filter thereby to vary the cutoff frequency of the filter and to maintain substantially constant amplitude of the fundmental wave form together with voltage comparator means for comparing the peaks of an alternating current quantity dependent upon the output of said filter with a direct current quantity proportional to the output of the filter, said comparator means thereby producing a pulse per cycle of said fundamental frequency.

Circuit arrangement for producing an open magnetic field

Abstract: A magnetic field for coupling to a load is produced by means of apparatus having first and second amplifiers operating in phase opposition and connected to a first oscillating circuit for generating a first oscillating voltage of predetermined fundamental frequency, an inductor producing the magnetic field being an element of the first oscillating circuit. A second oscillating circuit connected to the first circuit furnishes a second oscillating voltage having a frequency corresponding to the third harmonic of the fundamental frequency and includes a coil positioned relative to the load in such a manner that substantially no energy is transferred from the coil to the load.