Showing papers on "Fundamental frequency published in 1985"

Relative dominance of individual partials in determining the pitch of complex tones

Abstract: These experiments were conducted to determine the dominance of each partial in determining the residue pitch of a complex tone. Subjects were required to make pitch matches to a complex tone which had one partial slightly mistuned from its ‘‘correct’’ harmonic value. The shift in residue pitch was measured as a function of the frequency shift of the harmonic, for each harmonic in turn. For mistunings up to ±2%–3% the shift in residue pitch was approximately a linear function of the shift in the harmonic, but for greater mistunings the shift in residue pitch was reduced. The degree to which a given harmonic can influence residue pitch gives a measure of the dominance of that harmonic. The dominant harmonics were always contained within the lowest six harmonics (for fundamental frequencies of 100, 200, and 400 Hz), but there were marked individual differences in the exact distribution of dominance across harmonics. The level of a harmonic relative to adjacent harmonics can have a significant effect on its dominance. The implications of the results for theories of pitch perception are discussed.

Thresholds for the detection of inharmonicity in complex tones

Abstract: Thresholds were measured for the detection of inharmonicity in complex tones. Subjects were required to distinguish a complex tone whose partials were all at exact harmonic frequencies from a similar complex tone with one of the partials slightly mistuned. The mistuning which allowed 71% correct identification in a two‐alternative forced‐choice task was estimated for each partial in turn. In experiment I the fundamental frequency was either 100, 200, or 400 Hz, and the complex tones contained the first 12 harmonics at equal levels of 60 dB SPL per component. The stimulus duration was 410 ms. For each fundamental the thresholds were roughly constant when expressed in Hz, having a mean value of about 4 Hz (range 2.4–7.3 Hz). In experiment II the fundamental frequency was fixed at 200 Hz, and thresholds for inharmonicity were measured for stimulus durations of 50, 110, 410, and 1610 ms. For harmonics above the fifth the thresholds increased from less than 1 Hz to about 40 Hz as duration was decreased from 1610–50 ms. For the lower harmonics (up to the fourth) threshold changed much less with duration, and for the three shorter durations thresholds for each duration were roughly a constant proportion of the harmonic frequency. The results suggest that inharmonicity is detected in different ways for high and low harmonics. For low harmonics the inharmonic partial appears to ‘‘stand out’’ from the complex tone as a whole. For high harmonics the mistuning is detected as a kind of ‘‘beat’’ or ‘‘roughness,’’ presumably reflecting a sensitivity to the changing relative phase of the mistuned harmonic relative to the other harmonics. The results are discussed in relation to theories of pitch perception.

A spherical source model for low frequency volcanic earthquakes

Abstract: A resonant magma chamber is modeled by a spherically symmetric whole space consisting of a small gas-filled chamber surrounded by magma which is encased in country rock. Source boundary conditions are specified on the cavity boundary, simulating a possible sudden gas expansion in the magma. The simplicity of this model leads to an analytical closed form solution for the Fourier transform of radial displacement which predicts a peaked spectrum and an oscillating, decaying seismogram. For physically reasonable values of the rock and magma elastic properties and dimensions of the model, the dominant frequency of the signal is in the range of 1 to 5 Hz, near the values observed for low-frequency volcanic earthquakes and volcanic tremor. Furthermore, the seismograms and spectra bear resemblance to those observed for low-frequency earthquakes. The fundamental mode of oscillation is a pure radial “breathing” mode which has markedly different properties from single-cavity solutions. The fundamental frequency is insensitive to the magma chamber boundary radius when both the inner and outer radii are greater than specified values. This may help to explain the apparent similarity of the dominant frequency of volcanic earthquakes over a wide range of physical situations. The presence of an inner effective “bubble” of a certain minimum size is necessary for the existence of the dominant low fundamental frequency spectral peak. Although highly idealized, we believe that this fundamental fluid-solid cavity mode may provide an explanation for the observations of tremor and low-frequency volcanic earthquakes.

Period-doubling systems as small-signal amplifiers.

Abstract: Near the onset of a period-doubling bifurcation, any dynamical system can be used to amplify perturbations near half the fundamental frequency: The closer the bifurcation point, the greater the amplification. An analytic expression for the frequency response curve is derived explicitly for the driven Duffing oscillator. Results of analog simulations are presented to check the main features of the theory. We propose that the superconducting Josephson parametric amplifier is an example of this amplification process.

Infant pitch perception: evidence for responding to pitch categories and the missing fundamental.

Abstract: While numerous studies on infant perception have demonstrated the infant’s ability to discriminate sounds having different frequencies, little research has evaluated more sophisticated pitch perception abilities such as perceptual constancy and perception of the missing fundamental. In the present study 7–8‐month‐old infants demonstrated the ability to discriminate harmonic complexes from two pitch categories that differed in pitch by approximately 20% (e.g., 160 vs 200 Hz). Using a visually reinforced conditioned head‐turning paradigm, a number of spectrally different tonal complexes that contained varying harmonic components but signaled the same two pitch categories were presented. After learning the basic pitch discrimination, the same infants learned to categorize spectrally different tonal complexes according to the pitches signaled by their fundamental frequencies. That is, the infants showed evidence of perceptual constancy for the pitch of harmonic complexes. Finally, infants heard tonal complexes that signaled the same pitch categories but for which the fundamental frequency was removed. Infants were still able to categorize the harmonic complexes according to their pitch categories. These results suggest that by 7 months of age infants show fairly sophisticated pitch perception abilities similar to those demonstrated by adults.

Speech transformations based on a sinusoidal representation

Abstract: This paper presents a new speech analysis/synthesis technique based on a sinusoidal representation of the speech production mechanism but which is independent of pitch and the voiced/unvoiced speech state. The resulting synthetic speech preserves the waveform shape and is essentially perceptually indistinguishable from the original. The method provides the basis for a general class of speech transformations and is successfully applied to time-scale modification, frequency scaling, and scaling of pitch. Furthermore, these modifications can be performed with a time-varying rate of change, allowing, for example, continuous adjustment of a speaker's fundamental frequency and rate of articulation. Although the analysis/synthesis system was originally designed for single-speaker signals, it is equally capable of recovering and modifying nonspeech signals such as music, multi-speakers, marine biologic sounds, and speech in the presence of interferences such as noise and musical backgrounds.

Optimal design of a vibrating beam with coupled bending and torsion

Abstract: The problem of maximizing the fundamental frequency of a thin-walled beam with coupled bending and torsional modes is studied in this paper. An optimality criterion approach is used to locate stationary values of an appropriate objective function subject to constraints. Optimal designs with and without coupling are discussed. b h

Application of a computable model of human spatial vision to phase discrimination

Abstract: A computable model of human spatial vision is used to make predictions for phase-discrimination experiments. This model is being developed to deal with a broad range of problems in vision and was not specifically formulated to deal with phase discrimination. In the model, cross-correlation of the stimuli with an array of sensors produces feature vectors that are operated on by a position-uncertain ideal observer to simulate detection and discrimination experiments. In this report, the stimuli are compound sinusoidal gratings composed of a fundamental and a higher-frequency component added in various phases. Model predictions are compared with three key results from the literature: (1) the effect of the contrast of the fundamental on phase discrimination, (2) threshold phase difference as a function of the fundamental frequency, and (3) the contrast required for phase discrimination as a function of the frequency ratio of the two grating components. In the first two cases, the predictions capture the main features of the data, although quantitative discrepancies remain. In the third case, the model fails, and this failure suggests additional restrictions on the combination of information across sensors.

Bandpass filter with dielectric resonators

Abstract: A bandpass filter in which a plurality of dielectric resonators are arranged in an array is disclosed. Two metallic posts each having a length which is substantially equal to a quarter of the wavelength of the fundamental frequency (center frequency of the bandpass filter) are arranged one between the dielectric resonator located at one end of the array and an input connector and the other between the dielectric resonator located at the other end of the array and an output connector. This suppresses propagation of spurious modes, particularly propagation at a twice higher frequency than the fundamental frequency.

A wearable tactile intonation display for the deaf

Abstract: A wearable device is described which represents the fundamental frequency of voiced sounds as the locus of pitch-synchronous vibrotactile stimulation of the skin. The pitch extractor, which accepts inputs from either a microphone or an accelerometer, uses a combination of low-pass filtering and peak detection to generate a square wave whose frequency is half that of the fundamental frequency of the speech signal. Using a shift register and a clock, the first half of each cycle is timed, the result determining which of eight output channels is actuated during the second half. The output transducer array consists of eight miniature solenoids mounted in a small plastic box. The electronics package is worn on a belt and the solenoid array is mounted on the forearm. The system is powered by thee 9 V NiCad batteries and runs for 2 to 3 h between charges. Experiments with normally hearing subjects confirmed that single channel changes of stimulus location can be detected with relative ease. It was also demonstrated that the system permits discrimination among some of the principal intonation contours of English. The potential value of this device in the rehabilitation of hearing-impaired children is currently under investigation.

Phase-locked loop for a directly mixing synchronous AM-receiver

Abstract: A phase-locked loop is constituted by a controllable oscillator coupled through a phase detection arrangement and a low-pass filter to receive an input carrier applied to a signal input of the phase detection arrangement. In order to decrease the phase synchronization between a carrier locally generated in the loop and an input carrier, an unwanted DC offset generated during phase detection is reduced. The phase detection arrangement has first, second and third cascade-coupled mixer stages. An auxiliary mixing signal is applied from a signal generator to the first and third mixer stages. An input of one of the first and second mixer stages is coupled to the signal input of the phase detection arrangement and an input of the other of the two last-mentioned stages is coupled to an output of the controllable oscillator. The low-pass filter has a cut-off frequency lower than the fundamental frequency of the auxiliary mixing signal, and the fundamental frequency is lower than the frequency of the input carrier. The phase-locked loop is used to generate a synchronous RF carrier in a directly mixing AM receiver.

Measurement of Power Frequency Fluctuations Using the FFT

Abstract: A new method for detecting fluctuations in the fundamental frequency component of a power system, by relating it to a leakage coefficient in the FFT, is presented. The phenomenon of leakage in the FFT is used advantageously to increase spectral resolution. The leakage coefficient is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency. Theoretical aspects are considered along with a method for on-line implementation.

Second‐Order Harmonic in the Current Response to Sinusoidal Perturbation Voltage for Lead‐Acid Battery An Application to a State‐of‐Charge Indicator

Abstract: Distortion of the current response to sinusoidal alternating perturbation voltage has been quantitatively measured as a function of state of charge for commercially available lead-acid batteries. The input amplitude adopted here was greater than those used for ordinary impedance measurement. The distortion is represented as a power spectrum. Among higher order harmonics, that of the second one was selected for the parameter of a state-of-charge indicator. Excellent linearity was observed for the state of charge. It was also clarified that, compared to other parameters of the indicator, such as terminal voltage, impedance of fundamental tone, and concentration of sulfuric acid this parameter is less influenced by other factors during practical operation, such as discharge current and rest time.

Pitch shift of pure and complex tones induced by masking noise

Abstract: Psychoacoustic experiments were performed to measure the pitch‐shift effects of pure and complex tones resulting from the addition of a masking noise to the tonal stimuli. Harmonic residue tones with either two or three harmonics and a fundamental frequency of 200 Hz were chosen as test tones. The pitch shifts of virtual and spectral pitches of the residue tones were measured as a function of the intensity of a low‐pass noise with 600‐Hz cutoff frequency. The SPL of this noise varied between 30 and 70 dB. In another experiment, the pitch shifts of single pure tones corresponding to the frequencies and SPLs of the harmonics of the residue tones were measured using the same masking noise. The results from five subjects for the harmonic residue tones show only a weak dependence of pitch shift on masking noise intensity. This dependence exists for both spectral and virtual pitches. In the case of single pure tones, pitch shift depends more distinctly on noise intensity. Pitch shifts of up to 5% were found in the range of noise intensity investigated. The magnitude of pitch shift shows pronounced interindividual differences, but the direction of the shift effect is always the same. In all cases pitch increases with higher masking noise levels.

Vibration characteristics of hexagonal radial rib and hoop platforms

Abstract: Experiment and analysis have been used to characterize the modes of vibration of planar radial rib and hoop hexagonal platforms. Finite element analysis correlated very well with experimental results. The sensitivity of mode shapes and frequencies to cable stiffness and initial tension is presented. Threshold values have been identified, above which changes in cable stiffness do not affect the first few platform vibration modes. Primary vibration modes of the radial rib platform involve beam bending. Vibration modes of the hoop platform exhibit both beam bending and frame bending and torsion. Results indicate for low order polygonal structures, the radial rib concept produced a higher fundamental frequency. For high order polygonal structures, the hoop concept has the potential to achieve a higher fundamental frequency than the radial rib concept.

Method and apparatus for measuring surface properties

Abstract: PURPOSE:To separately determine the blur and distortion degrees of the image on the surface of an object to be measured, by calculating power intensity at fundamental frequency and the ratio of the sum of power intensities at a plurality of frequencies integer times the fundamental frequency to said power intensity at the fundamental frequency. CONSTITUTION:A rectangular wave pattern is projected to an image forming surface by an image forming optical system through reflection on the surface of an object to be measured to form an image. Subsequently, the special light intensity distribution on said image forming surface is subjected to Fourier transform and the sharpness gloss of the surface of the object to be measured is quantified on the basis of the magnitude of light power intensity at specific space frequency. In this case, the blur degree of the image is determined by the power intensity at fundamental frequency while the distortion degree of the image is determined by the ratio of the sum of power intensities at a plurality of frequencies integer times the fundamental space frequencies to the power intensity at the fundamental space frequency.

Coupling stage for coupling coded information on a phase line of an electric network

Abstract: of EP00938821. A coupling stage (K) for coupling information coded as a pulse pattern of pulses and pulse gaps, on a phase line of an electric network, preferably installed in a building, wherein the pulse pattern is an amplitude-modulated signal formed by the envelope of a sinusoidal carrier frequency signal having a frequency that is high compared to the network frequency and the fundamental frequency of the pulse pattern, and wherein the coupling stage (K) is at least temporarily highohmic, characterised in that the coupling stage (K) brings about low-ohmic coupling during the duration of a pulse pattern.

The effect of fundamental frequency on the discriminability between pure and tempered fifths and major thirds

Abstract: Thresholds were determined for discrimination between pure and tempered musical intervals (DTs) consisting of simultaneous complex tones. Tempered intervals are characterized by small frequency differences between those harmonics that coincide in pure intervals, Interference of these nearly coinciding harmonics gives rise to the perception of beats. Two parameters of beats were varied independently: (l) beat frequency and (2) depth of level variation (temporal envelope) as a measure of DT. DTs were determined for musical fifths and major thirds at a tone duration of 0.5 sec, The geometric mean of the fundamental frequency of the tones was varied in octave steps from 92.5 to 740 Hz, The beat frequency of the intervals was varied within a range of 2 to 64 Hz. The major result of our experiment was that, for a frequency range comprising 3 to 4 octaves, DTs do not depend on the frequency of the fundamentals, provided that the DTs are ordered according to beat frequency, When tempering (T) is expressed in cents and only those conditions are considered in which the degree of T corresponds to that found in the relevant tuning systems, it can be concluded that perceptual differences between tempered and pure fifths are increasingly irrelevant for tones lower than about middle C (262 Hz). Tempered major thirds, even those in a compromise tuning system such as that proposed by Silbermann (T=6 cents), can be discriminated from pure major thirds for all fundamental frequencies that are relevant in musical composition.

Optical distance-measuring method

Abstract: The invention relates to an optical distance-measuring method for touching the surface of an object to be measured by means of a primary light bundle emitted in the direction towards the surface of the object and focused in the region of the surface at a focal point. The focal point is set into periodic oscillations of a defined fundamental frequency and amplitude about a central position which can be varied in distance from the surface, and the intensity of the secondary light retroreflected from the surface is measured. At least one harmonic, namely the octave component of the fundamental frequency, is isolated from the intensity signal for the secondary light, and a search is made for the amplitude maximum which occurs when the central position of the focal point is displaced precisely into the surface. It is possible to increase the measurement accuracy or the resolution substantially by evaluating the octave component of the intensity signal, since the passage of the central position of the focal point through the surface is expressed as a sharply delimited amplitude peak in the octave component of the intensity signal. By contrast, in the passage of the focal point through the surface, the original intensity signal has a flat maximum, which can be determined using measurement methods customary to date but can be localised only with difficulty.