Showing papers on "Fundamental frequency published in 1983"

Visual cortical neurons as localized spatial frequency filters

Abstract: This paper relates to the receptive field properties of neurons in the primary visual cortex, i.e. the striate cortex, to current issues in spatial visual information processing. Particular attention is given to the fact that receptive field profiles of simple cells in the visual cortex often resemble even-symmetric or odd-symmetric Gabor filters; i.e. their receptive field profiles can be described by the product of a Gaussian and either a cosine or sine function. Their spatial frequency tuning is of medium bandwidth (~one octave) which is narrow enough for a cell to distinguish the third harmonic from the fundamental frequency for square-wave gratings of low spatial frequency. The responses of adjacent simple cells, tuned to the same spatial frequency, orientation, and direction, differ in their phase response to drifting sine-wave gratings by approximately either 90° or 180°. This latter result makes it possible to consider two adjacent simple cell pairs as operating like paired Gaussian-attenuated sine and cosine filters of Gabor filters for restricted regions of visual space. The entire set of simple cells provides a complete representation of the visual scene, yet each simple cell is unique in its response properties. At the complex cell stage, the cell's mean firing rate appears to represent the amplitude of a local Fourier coefficient, but phase information is seldom conveyed with much precision in the action potential code.

Pitch Determination of Speech Signals: Algorithms and Devices

Abstract: 1. Introduction.- 1.1 Voice Source Parameter Measurement and the Speech Signal.- 1.2 A Short Look at the Areas of Application.- 1.3 Organization of the Book.- 2. Basic Terminology. A Short Introduction to Digital Signal Processing.- 2.1 The Simplified Model of Speech Excitation.- 2.2 Digital Signal Processing 1: Signal Representation.- 2.3 Digital Signal Processing 2: Filters.- 2.4 Time-Variant Systems. The Principle of Short-Term Analysis.- 2.5 Definition of the Task. The Linear Model of Speech Production.- 2.6 A First Categorization of Pitch Determination Algorithms (PDAs).- 3. The Human Voice Source.- 3.1 Mechanism of Sound Generation at the Larynx.- 3.2 Operational Modes of the Larynx. Registers.- 3.3 The Glottal Source (Excitation) Signal.- 3.4 The Influence of the Vocal Tract Upon Voice Source Parameters.- 3.5 The Voiceless and the Transient Sources.- 4. Measuring Range, Accuracy, Pitch Perception.- 4.1 The Range of Fundamental Frequency.- 4.2 Pitch Perception. Toward a Redefinition of the Task.- 4.2.1 Pitch Perception: Spectral and Virtual Pitch.- 4.2.2 Toward a Redefinition of the Task.- 4.2.3 Difference Limens for Fundamental-Frequency Change.- 4.3 Measurement Accuracy.- 4.4 Representation of the Pitch Information in the Signal.- 4.5 Calibration and Performance Evaluation of a PDA.- 5. Manual and Instrumental Pitch Determination, Voicing Determination.- 5.1 Manual Pitch Determination.- 5.1.1 Time-Domain Manual Pitch Determination.- 5.1.2 Frequency-Domain Manual Pitch Determination.- 5.2 Pitch Determination Instruments (PDIs).- 5.2.1 Clinical Methods for Larynx Inspection.- 5.2.2 Mechanic PDIs.- 5.2.3 Electric PDIs.- 5.2.4 Ultrasonic PDIs.- 5.2.5 Photoelectric PDIs (Transillumination of the Glottis).- 5.2.6 Comparative Evaluation of PDIs.- 5.3 Voicing Determination - Selected Examples.- 5.3.1 Voicing Determination: Parameters.- 5.3.2 Voicing Determination - Simple Voicing Determination Algo-rithms (VDAs) Combined VDA-PDA Systems.- 5.3.3 Multiparameter VDAs. Voicing Determination by Means of Pattern Recognition Methods.- 5.3.4 Summary and Conclusions.- 6. Time-Domain Pitch Determination.- 6.1 Pitch Determination by Fundamental-Harmonic Extraction.- 6.1.1 The Basic Extractor.- 6.1.2 The Simplest Pitch Determination Device - Low-Pass Filter and Zero (or Threshold) Crossings Analysis Basic Extractor.- 6.1.3 Enhancement of the First Harmonic by Nonlinear Means.- 6.1.4 Manual Preset and Tunable (Adaptive) Filters.- 6.2 The Other Extreme - Temporal Structure Analysis.- 6.2.1 Envelope Modeling - the Analog Approach.- 6.2.2 Simple Peak Detector and Global Correction.- 6.2.3 Zero Crossings and Excursion Cycles.- 6.2.4 Mixed-Feature Algorithms.- 6.2.5 Other PDAs That Investigate the Temporal Structure of the Signal.- 6.3 The Intermediate Device: Temporal Structure Transformation and Simplification.- 6.3.1 Temporal Structure Simplification by Inverse Filtering.- 6.3.2 The Discontinuity in the Excitation Signal: Event Detection.- 6.4 Parallel Processing in Fundamental Period Determination. Multichannel PDAs.- 6.4.1 PDAs with Multichannel Preprocessor Filters.- 6.4.2 PDAs with Several Channels Applying Different Extraction Principles.- 6.5 Special-Purpose (High-Accuracy) Time-Domain PDAs.- 6.5.1 Glottal Inverse Filtering.- 6.5.2 Determining the Instant of Glottal Closure.- 6.6 The Postprocessor.- 6.6.1 Time-to-Frequency Conversion Display.- 6.6.2 f0 Determination With Basic Extractor Omitted.- 6.6.3 Global Error Correction Routines.- 6.6.4 Smoothing Pitch Contours.- 6.7 Final Comments.- 7. Design and Implementation of a Time-Domain PDA for Undistorted and Band-Limited Signals.- 7.1 The Linear Algorithm.- 7.1.1 Prefiltering.- 7.1.2 Measurement and Suppression of F1.- 7.1.3 The Basic Extractor.- 7.1.4 Problems with the Formant F2. Implementation of a Multiple Two-Pulse Filter (TPF).- 7.1.5 Phase Relations and Starting Point of the Period.- 7.1.6 Performance of the Algorithm with Respect to Linear Distortions, Especially to Band Limitations.- 7.2 Band-Limited Signals in Time-Domain PDAs.- 7.2.1 Concept of the Universal PDA.- 7.2.2 Once More: Use of Nonlinear Distortion in Time-Domain PDAs.- 7.3 An Experimental Study Towards a Universal Time-Domain PDA Applying a Nonlinear Function and a Threshold Analysis Basic Extractor.- 7.3.1 Setup of the Experiment.- 7.3.2 Relative Amplitude and Enhancement of First Harmonic.- 7.4 Toward a Choice of Optimal Nonlinear Functions.- 7.4.1 Selection with Respect to Phase Distortions.- 7.4.2 Selection with Respect to Amplitude Characteristics.- 7.4.3 Selection with Respect to the Sequence of Processing.- 7.5 Implementation of a Three-Channel PDA with Nonlinear Processing.- 7.5.1 Selection of Nonlinear Functions.- 7.5.2 Determination of the Parameter for the Comb Filter.- 7.5.3 Threshold Function in the Basic Extractor.- 7.5.4 Selection of the Most Likely Channel in the Basic Extractor.- 8. Short-Term Analysis Pitch Determination.- 8.1 The Short-Term Transformation and Its Consequences.- 8.2 Autocorrelation Pitch Determination.- 8.2.1 The Autocorrelation Function and Its Relation to the Power Spectrum.- 8.2.2 Analog Realizations.- 8.2.3 "Ordinary" Autocorrelation PDAs.- 8.2.4 Autocorrelation PDAs with Nonlinear Preprocessing.- 8.2.5 Autocorrelation PDAs with Linear Adaptive Preprocessing.- 8.3 "Anticorrelation" Pitch Determination: Average Magnitude Difference Function, Distance and Dissimilarity Measures, and Other Nonstationary Short-Term Analysis PDAs.- 8.3.1 Average Magnitude Difference Function (AMDF).- 8.3.2 Generalized Distance Functions.- 8.3.3 Nonstationary Short-Term Analysis and Incremental Time-Domain PDAs.- 8.4 Multiple Spectral Transform ("Cepstrum") Pitch Determination.- 8.4.1 The More General Aspect: Deconvolution.- 8.4.2 Cepstrum Pitch Determination.- 8.5 Frequency-Domain PDAs.- 8.5.1 Spectral Compression: Frequency and Period Histogram Product Spectrum.- 8.5.2 Harmonic Matching. Psychoacoustic PDAs.- 8.5.3 Determination of f0 from the Distance of Adjacent Spectral Peaks.- 8.5.4 The Fast Fourier Transform, Spectral Resolution, and the Computing Effort.- 8.6 Maximum-Likelihood (Least-Squares) Pitch Determination.- 8.6.1 The Least-Squares Algorithm.- 8.6.2 A Multichannel Solution.- 8.6.3 Computing Complexity, Relation to Comb Filters, Simplified Realizations.- 8.7 Summary and Conclusions.- 9. General Discussion: Summary, Error Analysis, Applications.- 9.1 A Short Survey of the Principal Methods of Pitch Determination.- 9.1.1 Categorization of PDAs and Definitions of Pitch.- 9.1.2 The Basic Extractor.- 9.1.3 The Postprocessor.- 9.1.4 Methods of Preprocessing.- 9.1.5 The Impact of Technology of the Design of PDAs and the Question of Computing Effort.- 9.2 Calibration, Search for Standards.- 9.2.1 Data Acquisition.- 9.2.2 Creating the Standard Pitch Contour Manually, Automatically, and by an Interactive PDA.- 9.2.3 Creating a Standard Contour by Means of a PDI.- 9.3 Performance Evaluation of PDAs.- 9.3.1 Comparative Performance Evaluation of PDAs: Some Examples from the Literature.- 9.3.2 Methods of Error Analysis.- 9.4 A Closer Look at the Applications.- 9.4.1 Has the Problem Been Solved?.- 9.4.2 Application in Phonetics, Linguistics, and Musicology.- 9.4.3 Application in Education and in Pathology.- 9.4.4 The "Technical" Application: Speech Communication.- 9.4.5 A Way Around the Problem in Speech Communication: Voice-Excited and Residual-Excited Vocoding (Baseband Coding).- 9.5 Possible Paths Towards a General Solution.- Appendix A. Experimental Data on the Behavior of Nonlinear Functions in Time-Domain Pitch Determination Algorithms.- A.1 The Data Base of the Investigation.- A.2 Examples for the Behavior of the Nonlinear Functions.- A.3 Relative Amplitude RA1 and Enhancement RE1 of the First Harmonic.- A.4 Relative Amplitude RASM of Spurious Maximum and Autocorrelation Threshold.- A.5 Processing Sequence, Preemphasis, Phase, Band Limitation.- A.6 Optimal Performance of Nonlinear Functions.- A.7 Performance of the Comb Filters.- Appendix B. Original Text of the Quotations in Foreign Languages Throughout This Book.- List of Abbreviations.- Author and Subject Index.

Speaking fundamental frequency: some physical and social correlates.

Abstract: Previous correlational studies have found no relationship between speaker height, weight and speaking fundamental frequency, although it has often been claimed that listeners can correctly identify the height, weight, and bodily build of speakers and that voice pitch is one of the cues used. In this study various social factors were controlled for, and contrasting samples of speech from each subject were analysed. Twelve men and 15 women, drawn from a socially homogeneous group, were asked to read two passages and to phonate the vowel /a:/ at "their lowest attainable pitch." The median speaking fundamental frequency from both passages was calculated and a measure of basal F0 was obtained from the phonation of /a:/. In contrast to other studies, a relationship was found between speaker height and median speaking fundamental frequency, but no relationship was found between speaker weight and F0. The correlation between median speaking fundamental frequency and height was significant only in the male sample ...

Fundamental and Harmonic Operation of Millimeter-Wave Gunn Diodes

Abstract: Pulsed and CW measurements in the range 26-110 GHz were performed on gallium arsenide (GaAs) Gunn diodes having active lengths of 1.8-2.6 µm, bonded into commercially available packages. The diodes were operated in full-height waveguides in the V-(WR-15), E-(WR-12), and W-(WR- 10) bands, using coaxial-bias circuits aud a disc-post resonator to provide the required resonance at their fundamental frequency in the range from about 25-65 GHz. Frequency and power measurements were performed up to 110 GHz on the fundamental, second, and third harmonics. The main emphasis of this experimental investigation has been the study of frequency changes caused by changes made in the various parameters of the disc, post, diode, diode package, and embedding waveguide sections.

Determination of Synchronous Machine Electrical Characteristics by Test

Abstract: A method of obtaining synchronous machine d and q axis impedances by test as function of frequency of d, q components is presented. The test involves running the machine at reduced speeds, with a line-to-line short circuit between phases, and temporarily applying excitation to produce line-to-line short circuit current at fundamental frequency corresponding to the particular running speed. Records of line-to-line voltages and short circuit current, along with measurement of rotor angle, are processed to yield d and q components of voltages, currents and flux linkages which turn out to be periodic functions of the fundamental frequency plus harmonics. Straight forward Fourier analysis yields the complex values of operational inductances or impedances L d (j2?), L q (j2?), Z d (j2?) or Z g (j2?) where ?is equal to the speed of the machine at which the tests are conducted.

Pitch period detection and chaining: method and evaluation.

Abstract: An algorithm is presented which detects quasi-periodic parts in a given speech signal, and provides the fundamental frequency for these parts. The algorithm analyses the structure of the time-amplitud

Microwave oscillator injection locked at its fundamental frequency for producing a harmonic frequency output

Abstract: A microwave oscillator suitable for millimeter wavelengths comprises a Gunn diode (3) coupled to a waveguide (1) by a resonant-cap structure (5,6). The diode (3) generates microwave energy both at a fundamental frequency f o which is below the cut-off frequency of the waveguide (1) and at a second harmonic frequency 2f o above cut-off. To control the generation of microwave energy at 2f o , energy at f o is coupled into the waveguide (1) from an adjacent further waveguide (9) above its cut-off, by means of an electric probe (8) extending close to the cap (5). The probe (8) may couple in a locking signal at or close to the free-running value of f o from another oscillator having better noise performance and electronic tuning, thereby locking 2f o to twice the frequency of the locking signal, or alternatively may couple to a varactor-tuned cavity resonant at f o .

Frequency‐independent impedances of soil‐structure systems in horizontal and rocking modes

Abstract: The frequency-independent foundation impedances, commonly used in soil-structure dynamic interaction problems, are developed for a circular footing resting on a homogeneous halfspace. As they ignore the structure attached to the foundation, the error introduced in the structural response may be 50 per cent or more in the neighbourhood of the fundamental frequency of the soil-structure system. The present study proposes a new method developed for most dynamic soil-structure interaction problems. The key idea is to retain for the frequency-independent impedances values computed for the fundamental frequency of the soil-structure system; thus these values include the dynamic characteristics of the whole soil-structure system and lead to a satisfactory approximation of the exact solution over a wide frequency range. The method is developed here for the horizontal and rocking modes of a structure with a circular base resting on a homogeneous halfspace. Numerical applications are given for a simple linear oscillator in order to make possible a thorough parametric study. The response of some idealized building-foundation systems to harmonic excitation or to a seismic input is next examined in order to illustrate the efficiency of the proposed model.

Tuning fork resonator

Abstract: A piezoelectric coupled mode turning fork using the fundamental vibration of a flexural mode coupled with the fundamental mode of torsion. The fundamental frequency of the torsional mode is adjusted by masses near the side edges of the tine tips, and the fundamental frequency of the flexural mode being adjusted by masses near the center of the tine tips which are nodes of the fundamental torsional mode.

Musical note display device

Abstract: An input audio signal is AD converted into digital data which is processed by a central processing unit (CPU) in which Fast Fourier Transform (FFT) operation and power spectrum calculation are effected. Furthermore, spectrum data obtained in this way is processed to obtain a fundamental tone to determine the pitch of each sound of the input audio signal. After the pitch is determined, data indicative of a given pattern is produced so that a musical note is indicated at an appropriate position on a staff displayed on a screen of a display unit. Such data from the CPU is fed via a video display processor to a video RAM to be stored therein where the video display processor produces a video signal fed to the display unit in turn. Since the fundamental tone does not necessarily have the highest level within the spectrum of the input audio signal, various ways for accurate determination of the pitch are used. Furthermore, a reference pitch preset in the musical note display device may be changed so as to be equal to a reference pitch emitted from a musical instrument or the like by changing sampling frequency of sampling pulses fed to an AD converter.

Effects of frequency‐modulated auditory tones on the voice fundamental frequency in humans

Abstract: The sensitivity of audio‐laryngeal reflex pathways to sinusoidal changes in the fundamental frequency of complex auditory tones (AF0) was assessed indirectly in three young adult human subjects. The subjects sustained phonation at constant voice fundamental frequency (VF0) and voice intensity while listening to a sawtooth tone whose AF0 varied over time in a sinusoidal fashion (rates=5–13 Hz). The subjects phonated at a low voice intensity so that the intensity of the auditory tone (80–85 dB SL) completely masked their voice. Using computer signal averaging and Fourier analysis techniques it was found that the sinusoidally modulated AF0 induced similar modulations in the VF0 signal. The VF0 modulations were extremely small in amplitude and showed large phase shifts relative to the auditory input. These findings are discussed in relation to the role of auditory feedback in phonatory control.

Electromagnetic geophysical surveying apparatus and system

Abstract: A frequency domain geophysical electromagnetic surveying system is provided in which intermittent primary fields having sharp terminations are generated in a cycle having a fundamental frequency by a transmitter (8), and a receiver (14) includes a gate (22) passing only secondary signals received during interruptions of the primary field, the gated signal being applied to filters (24, 25) turned to harmonics of the predetermined frequency. The filter outputs are synchronously demodulated (261, 26Q, 281, 28Q) to provide signals corresponding to at least the in-phase component of the secondary signal at the fundamental frequency, and preferably in-phase and quadrature components at at least two harmonics. The system can provide improved resolution particularly of the characteristics of inphase secondary signals received from terrain being surveyed.

Automatic analysis of voice fundamental frequency and intensity using a visi-pitch.

Abstract: This research note describes a method for automatic analysis of voice fundamental frequency and intensity using a Visi-Pitch Model 6087 and an Apple II computer equipped with an analog-to-digital c...

Effect of finite ground impedance on the propagation of acoustic pulses

Abstract: The propagation of an acoustic transient in the vicinity of a finite impedance ground plane has been numerically simulated. A waveform characteristic of a small explosive charge was selected for analysis. Pulse waveforms and amplitudes were computed for propagation distances from 3 to 3000 m, for microphone heights from 0 to 30 m, and for flow resistances from 10 to 1000 g cm−3 s−1. Typical values of atmospheric variables were assumed. Nonlinear propagation effects, atmospheric refraction, and turbulence were excluded from the analysis. This study indicates that finite ground impedance can significantly affect acoustic pulses from explosives. The need to consider ground effects when relating the results of small‐scale explosive tests to larger scale explosions is demonstrated. Finite impedance effects are small (<2 dB) for the pulse shape studied if the numerical distance of the fundamental frequency is less than 0.1. The surface wave term as formulated by Donato [J. Acoust. Soc. Am. 60, 34–39 (1976)] pro...

Transistor oscillator/frequency doubler with optimized harmonic feedback

Abstract: A microwave transistor oscillator/doubler comprising a Field-Effect Transistor with Terminals G, D and S in combination with a coupling network connected to the terminals G, D and S and composed of microstrip lines with lengths equal to a quarter wavelength at the second harmonic of a fundamental frequency. The doubler further comprises a bias circuit for supplying appropriate voltages to the FET terminals, and an impedance coupler for coupling from the FET D-S terminals to a waveguide load. The coupling network optimizes feedback at the second harmonic between the D-S and G-S ports of the FET to prevent destructive harmonic feedback interaction with the desired signal while providing optimum conditions for feedback at the fundamental frequency. The bias circuit is connected to the coupling network and includes a second network of transmission line elements of lengths equal to a quarter wavelength at the fundamental in order to prevent dissipation of the fundamental frequency therein.

Spatial frequency characteristics of brisk and sluggish ganglion cells of the cat's retina.

Abstract: Receptive fields of cat retinal ganglion cells were stimulated by a drifting sinusoidal luminance pattern of fixed (50%) contrast and the amplitude of the fundamental frequency component of response was determined as a function of spatial frequency. Frequency response functions for most cells were unimodal and skewed towards zero frequency when plotted on linear scales. At a fixed retinal location, cells of different classes had different frequency response functions. Heterogeneity within some of the classes could be largely removed by normalizing the axes, thus, revealing a common shape of function for the class. At a fixed retinal location, the maximum response obtained at each spatial frequency was always obtained from a cell of the brisk, rather than sluggish, classes. Spatial frequency resolution was highest for brisk-sustained cells and usually lowest for brisk transient cells.

High efficiency high frequency power oscillator

Abstract: The invention relates to a high frequency, high mechanical energy output apparatus comprising a transducer, a filter circuit, and a driving circuit. The transducer and the filter circuit are serially coupled together, and the transducer operates at its fundamental frequency of oscillatory motion. The driving circuit serves to drive the transducer at its fundamental frequency and comprises first and second active devices, wherein each active device has an output circuit and a control circuit. Each of the active devices are cooperatively connected together and are responsive to control signals for producing an alternating output signal. There is also provided means coupling the output circuits of the active devices to the transducer so that an alternating series current signal is applied serially through the transducer. The filter circuit filters from the alternating series current signal substantially all harmonics of the fundamental frequency of oscillation of the transducer to produce a filtered series current signal. There is also provided means for coupling the filtered series current signal to the control circuits of the active devices such that the filtered series current signal constitutes the control signal for controlling each of the first and second active devices for producing an output signal from the driving circuit substantially at the fundamental frequency.

Embedding impedance of a millimeter wave Schottky mixer: Scaled model measurements and computer simulations

Abstract: Using scaled model measurements at 2.5–12 GHz the embedding network of a 3 mm Schottky diode mixer has been developed. The noise performance of a cryogenic millimeter wave receiver was simulated by computer applying the developed equivalent circuit and diode parameters. The effects of impedance match at the fundamental frequency as well as at harmonic frequencies were studied. Also the effect of diode I-V-curve steepness was studied. The calculated results were compared with the experimental noise performance.

Wind tunnel measurements of blade/vane ratio and spacing effects on fan noise

Abstract: Introduction R turbofan engine designs aimed at increasing the structural rigidity and reducing the weight of the engine frame lead to a reduced number of stator vanes and an abandonment of vane-blade ratios greater than required for fundamental tone cutoff.' These designs, which consider stator solidity aerodynamic constraints, consist of a relatively few longer chord, larger thickness stator vanes which are load-carrying members of an integrated vane-frame. Basic acoustic data on the effects of vane-blade ratio and spacing under conditions which simulate flight are needed to determine the acoustic consequences of adopting alternate designs such as the integrated vane-frame. Expected noise consequences of varying fan stage design parameters, such as vane-blade ratio and rotor-stator spacing have often been masked in static testing. This is largely due to the fact that the fundamental blade passing tone level and, to a lesser extent, the tone harmonics levels are controlled by rotor-inflow interaction mechanisms,' which mask the rotor-stator interaction noise. The blade passing tone level of a fan designed for fundamental tone cutoff is greatly reduced with forward velocity. Noise studies performed in an anechoic wind tunnel' have shown results similar to those obtained in flight tests. In the present study the noise of a 50.8-cm-diam research turbofan simulator was measured in the anechoic wind tunnel described in Refs. 6 and 7. Both vane-blade ratio and rotorstator spacing were varied. Specifically, two stator vane numbers were chosen to achieve a cuton and cutoff condition with respect to propagation of the fundamental rotor-stator interaction tone as predicted by the theory of Ref. 8. The noise associated with each of these stator configurations was measured at three rotor-stator spacings ranging from 0.5 to 2.0 rotor chords.

Amplitude modulator forms two phase-shifted pulse trains and combines them

Abstract: A system and method for amplitude modulating a carrier signal with an audio or other information input signal relies on multivibrators and comparators initiating a logic controlled processing technique for providing two sinusoids, each a fundamental frequency waveform, the two having a mutual phase relationship defined by intermediate processing steps such that they differ in phase from 0 to 180 electrical degrees. The comparators output first resultant pulses when the carrier signal is greater than the amplitude of the audio or other information input signal. The first resultant pulses are input to a logic processing network to trigger multivibrators which output overlapping 180° wide pulses, respective phase shifted resultant signal waveforms being formed from the respective comparator outputs. In the output stage, the respective resultant waveforms are amplified and filtered to form the two sinusoids which are added vectorially to form an amplitude modulated output signal which varies linearly with the audio or information input signal.

Stable sine wave generator

Abstract: A sine wave generator which utilizes a PROM for storing a predetermined bit pattern which is converted to a corresponding pulse waveform generated in response to a very accurate and stable clock pulse. The pulse waveform is shifted to a very exacting voltage level and is filtered by a band-pass filter to derive the desired fundamental frequency sine wave. The amplitude and frequency stable sine wave may be utilized in linear variable differential transformer (LVDT) apparatus for measuring the position of a controlled object such as a turbine valve. The arrangement may also be utilized for generating additional sine waves bearing some predetermined phase relationship with respect to one another for other control or signal processing applications.

Harmonic noise control in chopper type voltage regulators

Abstract: Voltage regulators of the waveform chopping type operable with alternating current sources are operated in a mode wherein a wave train complementary to the chopping wave train is provided with the property that each of the wave trains has equal amplitude and inverse polarity harmonics. Thus the two wave trains may be added together to cancel out all the noise introduced by the chopping. This is done by synchronously switching the respective wave trains in two corresponding processing channels leading to two respective power output channels, wherein one channel has incorporated therein amplitude regulation means, preferably of the feedback type. To remove the noise components, the higher frequency harmonics are isolated from the fundamental frequency which serves as the power supply medium, and then the equal amplitude and opposite sense harmonics are added together to cancel the noise components.

Odd harmonic signal generator

Abstract: Odd harmonic generator includes two amplitude limiting amplifiers and a frequency selective signal combining network. Sinusoidal signal at frequency of chrominance subcarrier is applied to inputs of both amplifiers. The first amplifier provides signal comprising fundamental and odd harmonic frequency components. The second amplifier provides signal comprising a fundamental frequency component and odd harmonic frequency components that are comparatively much smaller than the odd harmonic frequency components of the first amplifier's output signal. Signals are combined so that fundamental frequency components offset. Output signal at third harmonic of chrominance subcarrier frequency is used as clock signal for CCD comb filter in a color TV receiver.

A Study of the Reading and Speaking Fundamental Vocal Frequency of Aging Black Adults.

Abstract: The present study explored the relationships between fundamental frequency means and range extents for black adults in three decade intervals from 50-79 years of age during two speaking tasks. One hundred thirty-three males and 144 females participated in a spontaneous speaking task. Only 28 males and 65 females were able to participate in the reading activity. The results of the reading central tendencies for males suggested that the mean fundamental frequency increases with age for each decade interval (107.14 Hz, 111.00 Hz, and 129.09 Hz, respectively). The males in the 50and 60-year decades had significantly lower means than the 70-year decade group. The mean reading ranges were 80.71 157.14 Hz, 76.50 185.50 Hz and 89.54 178.63 Hz for the three decade groups, respectively. The range of the 60-year decade group was significantly wider than that of the 50-year decade group. No other significant differ­ ences in reading ranges for males were found.