Showing papers on "Fundamental frequency published in 1986"

Adaptive comb filtering for harmonic signal enhancement

Abstract: A new algorithm is presented for adaptive comb filtering and parametric spectral estimation of harmonic signals with additive white noise. The algorithm is composed of two cascaded parts. The first estimates the fundamental frequency and enhances the harmonic component in the input, and the second estimates the harmonic amplitudes and phases. Performance analysis provides new results for the asymptotic Cramer-Rao bound (CRB) on the parameters of harmonic signals with additive white noise. Results of simulations indicate that the variances of the estimates are of the same order of magnitude as the CRB for sufficiently large data sets, and illustrate the performance in enhancing noisy artificial periodic signals.

Thresholds for hearing mistuned partials as separate tones in harmonic complexes

Abstract: When a low harmonic in a harmonic complex tone is mistuned from its harmonic value by a sufficient amount it is heard as a separate tone, standing out from the complex as a whole. This experiment estimated the degree of mistuning required for this phenomenon to occur, for complex tones with 10 or 12 equal‐amplitude components (60 dB SPL per component). On each trial the subject was presented with a complex tone which either had all its partials at harmonic frequencies or had one partial mistuned from its harmonic frequency. The subject had to indicate whether he heard a single complex tone with one pitch or a complex tone plus a pure tone which did not ‘‘belong’’ to the complex. An adaptive procedure was used to track the degree of mistuning required to achieve a d’ value of 1. Threshold was determined for each ot the first six harmonics of each complex tone. In one set of conditions stimulus duration was held constant at 410 ms, and the fundamental frequency was either 100, 200, or 400 Hz. For most conditions the thresholds fell between 1% and 3% of the harmonic frequency, depending on the subject. However, thresholds tended to be greater for the first two harmonics of the 100‐Hz fundamental and, for some subjects, thresholds increased for the fifth and sixth harmonics. In a second set of conditions fundamental frequency was held constant at 200 Hz, and the duration was either 50, 110, 410, or 1610 ms. Thresholds increased by a factor of 3–5 as duration was decreased from 1610 ms to 50 ms. The results are discussed in terms of a hypothetical harmonic sieve and mechanisms for the formation of perceptual streams.

Speech transformations based on a sinusoidal representation

Abstract: In this paper a new speech analysis/synthesis technique is presented which provides the basis for a general class of speech transformations including time-scale modification, frequency scaling, and pitch modification. These modifications can be performed with a time-varying change, permitting continuous adjustment of a speaker's fundamental frequency and rate of articulation. The method is based on a sinusoidal representation of the speech production mechanism which has been shown to produce synthetic speech that preserves the wave-form shape and is perceptually indistinguishable from the original. Although the analysis/synthesis system was originally designed for single-speaker signals, it is also capable of recovering and modifying nonspeech signals such as music, multiple speakers, marine biologic sounds, and speakers in the presence of interferences such as noise and musical backgrounds.

Route to chaos in porous-medium thermal convection

Abstract: A pseudo-spectral numerical scheme is used to study two-dimensional, single-cell, time-dependent convection in a square cross-section of fluid saturated porous material heated from below. With increasing Rayleigh number R convection evolves from steady S to chaotic NP through the sequence of bifurcations S→P(1)→QP2→P(2)→NP, where P(1) and P(2) are simply periodic regimes and QP2 is a quasi-periodic state with two basic frequencies. The transitions (from onset of convection to chaos) occur at Rayleigh numbers of 4π2, 380–400, 500–520, 560–570, and 850–1000. In the first simply periodic regime the fundamental frequency f1 varies as . The chaotic states are characterized by spectral peaks with at least 3 fundamental frequencies superimposed on a broadband background noise. The time dependence of these states arises from the random generation of tongue-like disturbances within the horizontal thermal boundary layers. Transition to the chaotic regime is accompanied by the growth of spectral components that destroy the centre-symmetry of convection in the other states. Over-truncation can lead to spurious transitions and bifurcation sequences; in general it produces overly complex flows.

Harmonics from Transformer Saturation

Abstract: Saturation effects in transformers and shunt reactors can produce harmonics in power systems. Their magnitude can sometimes be found with an electromagnetic transients program, by going from an approximate linear ac steady-state solution directly into a transient simulation in which the nonlinear effects are included. In lightly damped systems, such simulations can take a long time, however, before the distorted steady state is reached. Therefore, another method was developed which uses superposition of steady-state phasor solutions at the fundamental frequency and at the most important harmonic frequencies, with nonlinear inductances represented as harmonic current sources. This method can either be used by itself, or as an improved initialization procedure for electromagnetic transients programs.

Pitch detection using the short-term phase spectrum

Abstract: A new frequency domain method for determining the fundamental frequency of speech is presented in this paper. This method uses the information contained in the short-term phase spectral whereas the previous methods were limited to the amplitude spectrum. The short-term spectrum is computed by DFT and it is interpreted as the output of a bank of band-pass overlapping filters. Harmonic components are detected by searching for sets of three contiguous filters having the same instantaneous frequency. The frequency of a detected harmonic is given by the instantaneous frequency itself. A conventional harmonic numbering algorithm is used to convert the set of detected harmonics to a value of the fundamental frequency. Preliminary results show the validity of the method.

Synthesis of natural sounding pitch contours in isolated utterances using hidden Markov models

Abstract: A novel technique is introduced for characterizing prosodic structure and is used for speech synthesis. The mechanism consists of modeling a set of observations as a probabilistic function of a hidden Markov chain. It uses mixtures of Gaussian continuous probability density functions to represent the essential, perceptually relevant structure of intonation by observing movements of fundamental frequency in monosyllabic words of varying phonetic structure. High-quality speech synthesis, using multipulse excitation, is used to demonstrate the power of the HMM in preserving the naturalness of the intonational meaning, conveyed by the variation of fundamental frequency and duration. The fundamental frequency contours are synthesized using a random number generator from the models, and are imposed on a synthesized prototype word which had the intonation of a low fall. The resulting monosyllabic words with imposed synthesized fundamental frequency contours show a high level of naturalness and are found to be perceptually indistinguishable from the original recordings with the same intonation. The results clearly show the high potential of hidden Markov models as a mechanism for the representation of prosodic structure by naturally capturing its essentials.

Testing a model of intonation in a tone language

Abstract: Schematic fundamental frequency curves of simple statements and questions are generated for Hausa, a two‐tone language of Nigeria, using a modified version of an intonational model developed by Garding and Bruce [Nordic Prosody II, edited by T. Fretheim (Tapir, Trondheim, 1981), pp. 33–39]. In this model, rules for intonation and tones are separated. Intonation is represented as sloping grids of (near) parallel lines, inside which tones are placed. The tones are associated with turning points of the fundamental frequency contour. Local rules may also modify the exact placement of a tone within the grid. The continuous fundamental frequency contour is modeled by concatenating the tonal points using polynomial equations. Thus the final pitch contour is modeled as an interaction between global and local factors. The slope of the intonational grid lines depends at least on sentence type (statement or question), sentence length, and tone pattern. The model is tested by reference to data from nine speakers of K...

Acoustic fish behavioural control device

Abstract: An acoustic device for eliciting either attraction or repulsion behavioral responses in fish comprises a water tight enclosure having a radiating surface rigidly supported in one end thereof. Drive means for the radiating surface are provided with the capability of causing the radiating surface to vibrate at its resonant frequencies so that an acoustic signal is generated capable of a peak sound pressure level of at least 0.5 kPa (0 to peak) at a distance of 3 meters from the radiating surface. The signal generated has one fundamental frequency component in the range 20 to 1000 Hz and a plurality of resonant and harmonic frequencies associated with said fundamental frequency. The drive means, radiating surface and enclosure coact to generate an acoustic signal having characteristics such as resonant frequencies, peak pressures and temporal patterns which may be selectively optimized to produce the desired behavioral response.

Perceptual Compensation for Segmentally Conditioned Fundamental Frequency Perturbation

Abstract: The paper deals with the role of two types of segmentally conditioned fundamental frequency (F₀) perturbation in speech perception, i. e. the differences in F₀ between high and low vowels

Distribution line carrier system

Abstract: PURPOSE:To reduce the influence of harmonic noise and to improve considerably a bit error rate by setting the transmission signal frequency to an integer-fold of system fundamental frequency and analyzing high frequencies on a basis of a system voltage in the reception side and performing always overall discrimination with stray higher harmonics to receive bits. CONSTITUTION:After confirming that there are no accidents or the like in the system, an address calling a transmission terminal is transmitted. After confirming that signals transmitted from the other slave stations do not exist, a master station starts reading with a voltage and a current in its own end as the input and defines the point of zero voltage as zero of the reference time in accordance with these voltage and current and obtains Fourier coefficients cm and dm of the signal frequency and Fourier coefficients cn and dn corresponding to another signal frequency near said signal frequency if said signal frequency is about m-fold fundamental wave. The slave station obtains Fourier coefficients of higher harmonics of the M-th order and the N-th order of the slave station current on a basis of zero voltage similarly to the master station and transmits them as data. The master station compares this data with cm, dm, cn, and dn measured in its own end to discriminate whether they are different or not; and if the result is within a determined range, it is judged to be normal, and transmission of regular data is requested to the slave station.

A High Q Cavity Stabilized Gunn Oscillator at 94 GHz

Abstract: The set up and the performance of a 94 GHz second harmonic Gunn oscillator that is cavity stabilized at its fundamental frequency is described. The cavity has a quality factor of about 7000 and reduces the phase noise by nearly 40 dB. The oscillator generates an output power of 40 mW, sufficient to drive low noise balanced mixers, to synchronize Impatt oscillators or to operate as a reference source in coherent radar systems.

Detailed spectral analysis of a female voice

Abstract: Several thousand DFT magnitude spectra have been produced for a selected sample of speech from a single female speaker having a pleasant voice quality. The speaker sustained a number of different vowels while undertaking different laryngeal gestures including (1) slow 1‐oct pitch glides up or down and (2) reiterant imitations of different sentences, using either [?V] of [hV] replacements for the pattern of stressed and unstressed syllables in each sentence, where [V] is one of six English vowels. An attempt has been made to quantify the effects on the harmonic spectrum of changes to fundamental frequency, syllable stress, and position of the syllable in the utterance. Also of interest is the detailed way that voicing is initiated and terminated in laryngealized versus breathy onsets and offsets. Previous analyses that used inverse filtering to study the glottal waveform seem to have missed several important aspects of the source spectrum and its change over time. Our analysis reveals the presence of considerable random breathiness noise at frequencies above 2 kHz over portions of many utterances. The strength of the fundamental component and of the various formant peaks relative to overall rms energy in the signal under all of the conditions outlined above have been quantified. There is variation in both the general tilt of the harmonic spectrum and the strength of the fundamental component depending largely on the (presumed) degree to which the larynx is spread/constricted. Locations of spectral zeros have been studied and related to the duration of the open part of glottal period. Synthesis has also been attempted using a modified version of the Klattalk synthesizer, which provides direct control over voicing source open period, source spectral tilt, breathiness noise, and degree of instability in the fundamental frequency contour (the latter parameter being particularly important for natural synthesis of a vowel sustained at constant pitch). Sentences spoken by replacing all of the syllables by [?V] were somewhat easier to synthesize—than sentences spoken by replacing all of the syllables by [hV]. The reason appears to be that in the latter materials, additional spectral peaks—presumably related to tracheal resonances—were sometimes observed in the vowel spectra. Except for this possibly important aspect of voice quality, the synthesis results are very encouraging; source control parameters and formant parameters are monotonic slowly varying continuous functions, suggesting that rules for the synthesis of more natural female voices might be formulated as a next step. [Work supported in part by NIH.]

Second harmonic generation by carbamic acid derivatives

Abstract: Devices for and method of generating coherent second harmonic light radiation. The devices comprise a laser source of coherent light radiation at a fixed fundamental frequency, a crystalline N-aryl carbamyl compound that crystallizes in a non-centrosymmetric configuration, means for directing the output radiation of the laser onto the crystalline chiral N-aryl carbamyl compound, and output means for utilizing the second harmonic frequency.

Circuit for a flash stroboscope for examining vocal chord functions

Abstract: A circuit for a flash stroboscope for examining vocal chord functions has a number of band-pass filters connected in parallel which have different cut-off frequencies. The acoustic signal generated by the vocal chords is fed to the inputs of these filters as an electrical signal after conversion in an electro-acoustic transducer. The output signal or fundamental wave signal allowed to pass by filter with a fundamental frequency of interest for the examination is supplied to a lamp circuit, which activates a flash lamp by trigger pulses generated from the fundamental wave. The band-pass filters are scanned automatically and successively to determine the presence of an output signal having the fundamental frequency of interest. The scanning operation is stopped upon detection of an output signal of this frequency at one of the filter outputs, so that the output of this filter can be connectd to the lamp circuit. The scanning operation is repeated cyclically so that the circuit can always be updated to the existing condition in the event of possible changes of the fundamental wave frequency.

Matching the pitch of a mistuned harmonic in an otherwise periodic complex tone

Abstract: Listeners adjusted the frequency of a sine tone to match the pitch of a single mistuned harmonic in a complex tone consisting of 16 harmonics. Fundamental frequencies were 200, 400, or 800 Hz, and mistunings ranged from 0.5% to 8.0%. The successful matches, those close to the actual mistuned harmonic, show highly consistent and unexpected pitch shift effects; the pitch shifts can be twice as large as the frequency shifts, for both positive and negative frequency shifts. The percentage of matches which are successful provides an estimate of a listener's ability to segregate the mistuned component from the complex tone. Best performance occurs for mistuned harmonics in the region of spectral dominance. The highest frequency which can be segregated is a decreasing function of the fundamental frequency. The latter result suggests that the segregation operation depends upon both place and time coding in the auditory system. [Work supported by the NIH, the NSF, and the CHRS—France.]

Frequency identification by complex spectrum

Abstract: The fundamental frequency of signal is one of the important information. We can obtain the frequency of periodic wave from the peak of spectrum calculated by FFT. But the resolution of peak frequency is not so high. To get higher resolution, some methods have been proposed. They require a great deal of calculation. To improve the calculation speed, this paper proposes a new method to estimate the fundamental frequency in short observation interval using the complex spectrum. The phase component of complex spectrum gives us a useful information to increase the resolution. Using the characteristics of complex spectrum, we obtained the peak frequency with negligible error. This method requires a little caliclation. The frequency of signal can be estimated in real time when an array processor is used.

An Investigation of the Fundamental-Frequency Impedance of a Single-Phase Distribution Lateral

Abstract: Fundamental-frequency impedance measurements conducted on a single-phase distribution feeder suggest that conventional methods of calculating line-impedance can lead to gross errors. These errors are shown to be due to lack of adequate modeling of the current division between earth and neutral as determined by neutral grounding. Models that include the effects of self-and mutual-impedances, pole-ground resistances, and endpoint impedances are presented and the results are compared with field test results. It is shown how Carson's equations can be correctly used in evaluating some of the model parameters. Simulation studies of the effects of pole-ground resistances on line impedance are presented. The use of probabilistic simulation in computing the statistics of impedance parameters, when pole-ground resistances are not accurately known, is also illustrated. Extensions of the approach to higher frequencies and to three-phase circuits are indicated.

Wideband tunable 140 GHz second-harmonic InP-TED oscillator

Abstract: A second-harmonic InP-TED oscillator, with an output power of more than 3dBm at 144 GHz and tunable over a 10% frequency range, has been developed. The design incorporates two waveguide resonators. One resonator determines the fundamental frequency of oscillation and the other optimises the second-harmonic output power.

A Microwave Frequency Halver with Conversion Gain

Abstract: A novel frequency halver circuit is presented, based on the concept of parametric division using a Schottky diode This technique utilizes the gate to source Schottky diodes of two FETs in a half frequency, resonant loop configuration Measurements of such a frequency divider, for an input signal in X-band, show conversion gain with good suppression of the fundamental frequency Unlike its predecessors, it is characterized by a low turn-on threshold

Electromagnetic surveillance system with improved signal processing

Abstract: Markers carried in an interrogation zone by articles to be monitored are subjected to an electromagnetic field varying in time at a fundamental frequency and respond by generating signals at harmonic frequencies of the fundamental frequency, characteristic of soft magnetic materials. The system comprises: a transmitter for the electromagnetic field signal; a receiver and processor for signals generated by the article markers; and, a clock for phase locking the transmitter, the receiver and processor with one another. Signal information corresponding to at least one even order harmonic of the fundamental frequency in the received signals is tested for, and the duration thereof is measured. Signal information corresponding to at least one odd order harmonic is tested for, and if present, the phase angle thereof is measured. An alarm condition is signaled whenever the at least one even order harmonic endures for a predetermined time period, and the at least one odd harmonic, if present, is in proper phase with the transmitted signal. The alarm is inhibited whenever the phase angle of the at least one odd harmonic is improper, or broad band noise with random phase angles is detected and measured. Sensitivity to valid alarm conditions is substantially increased and occurrence of false alarms is substantially eliminated.

Multi-frequency electro-acoustic transducer

Abstract: A transducer of the Tonpilz type comprises a horn (1), a motor (2) constituted by a piezo-electric stack of ceramics (5) alternating with electrodes 7a, 7b and a counter-mass (3). This transducer can transmit on a first band centred on a low frequency fb which is the fundamental frequency of the whole of the structure, and on a second frequency fh, of the order of three times fb, which is both the intrinsic frequency of the longitudinal mode of vibration of the whole of the structure and one of the fluttering frequencies of the horn alone. One application is the construction of high power sonar transmitters.