Showing papers on "Noise published in 1982"
TL;DR: In this article, the authors present a review of the methods of Kalman filtering in attitude estimation and their development over the last two decades, focusing on three-axis gyros and attitude sensors.
Abstract: HIS report reviews the methods of Kalman filtering in attitude estimation and their development over the last two decades. This review is not intended to be complete but is limited to algorithms suitable for spacecraft equipped with three-axis gyros as well as attitude sensors. These are the systems to which we feel that Kalman filtering is most ap- plicable. The Kalman filter uses a dynamical model for the time development of the system and a model of the sensor measurements to obtain the most accurate estimate possible of the system state using a linear estimator based on present and past measurements. It is, thus, ideally suited to both ground-based and on-board attitude determination. However, the applicability of the Kalman filtering technique rests on the availability of an accurate dynamical model. The dynamic equations for the spacecraft attitude pose many difficulties in the filter modeling. In particular, the external torques and the distribution of momentum internally due to the use of rotating or rastering instruments lead to significant uncertainties in the modeling. For autonomous spacecraft the use of inertial reference units as a model replacement permits the circumvention of these problems. In this representation the angular velocity of the spacecraft is obtained from the gyro data. The kinematic equations are used to obtain the attitude state and this is augmented by means of additional state-vector components for the gyro biases. Thus, gyro data are not treated as observations and the gyro noise appears as state noise rather than as observation noise. It is theoretically possible that a spacecraft is three-axis stabilized with such rigidity that the time development of the system can be described accurately without gyro information, or that it is one-axis stabilized so that only a single gyro is needed to provide information on the time history of the system. The modification of the algorithms presented here in order to apply to those cases is slight. However, this is of little practical importance because a control system capable of such
1,266 citations
TL;DR: In this paper, the estimation procedure presented here makes use of "backward prediction" in addition to singular value decomposition (SVD) for accurate estimation of closely spaced frequencies of sinusoidal signals in noise.
Abstract: We have presented techniques [1] - [6] based on linear prediction (LP) and singular value decomposition (SVD) for accurate estimation of closely spaced frequencies of sinusoidal signals in noise. In this note we extend these techniques to estimate the parameters of exponentially damped sinusoidal signals in noise. The estimation procedure presented here makes use of "backward prediction" in addition to SVD. First, the method is applied to data consisting of one and two exponentially damped sinusoids. The choice of one and two signal components facilitates the comparison of estimation error in pole damping factors and pole frequencies to the appropriate Cramer-Rao (CR) bounds and to traditional methods of linear prediction. Second, our method is applied to an example due to Steiglitz [8] in which the data consists of noisy values of the impulse response samples (composed of many exponentially damped sinusoids) of a linear system having both poles and zeros. The poles of the system are accurately determined by our method and the zeros are obtained subsequently, using Shanks' method.
881 citations
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TL;DR: In this paper, a non-stationary autocorrelation function for 1/f noise was developed to demonstrate that its present behavior is equally correlated with both the recent and distant past.
Abstract: 1/f noise is a nonstationary random process suitable for modeling evolutionary or developmental systems. It combines the strong influence of past events on the future and, hence somewhat predictable behavior, with the influence of random events. Nonstationary autocorrelation functions for 1/f noise are developed to demonstrate that its present behavior is equally correlated with both the recent and distant past. The minimum amount of memory for a system that exhibits 1/f noise is shown to be one state variable per decade of frequency. The system condenses its past history into the present values of its state variables, one of which represents an average over the most recent 1 unit of time, one for the last 10 time units, 100 units, 1000, 10000, and so on. Each such state variable has an equal influence on present behavior.
879 citations
TL;DR: The important new feature of the proposed algorithms is their ability to ignore redundant data and the efficient data extraction property of the new algorithms is achieved with small computational effort and with improved performance when compared to the least square algorithm.
725 citations
TL;DR: The harmonics-to-noise (H/N) ratio proved useful in quantitatively assessing the results of treatment for hoarseness and showed a highly significant agreement between H/N calculations and the subjective evaluations of the spectrograms.
Abstract: Degree of hoarseness can be evaluated by judging the extent to which noise replaces the harmonic structure in the spectrogram of a sustained vowel. However, this visual method is subjective. The present study was undertaken to develop the harmonics‐to‐noise (H/N) ratio as an objective and quantitative evaluation of the degree of hoarseness. The computation is conceptually straightforward; 50 consecutive pitch periods of a sustained vowel /a/ are averaged; H is the energy of the averaged waveform, while N is the mean energy of the differences between the individual periods and the averaged waveform. Recordings of 42 normal voices and 41 samples with varying degrees of hoarseness were analyzed. Two experts rated the spectrogram of each voice sample, based on the amount of noise relative to that of the harmonic component. The results showed a highly significant agreement (the rank correlation coefficient = 0.849) between H/N calculations and the subjective evaluations of the spectrograms. The H/N ratio also proved useful in quantitatively assessing the results of treatment for hoarseness.
548 citations
04 May 1982
TL;DR: In this paper, the Ffowcs Williams-Hawkings (FW-H) equation is used for the calculation of the noise produced by helicopter rotors, which can be used to control the noise of existing helicopters by avoiding noisy regimes of flight or by redesigning the main and tail rotors.
Abstract: An accurate prediction of the noise produced by helicopters requires a good understanding of the noise generating mechanisms involved Such an understanding can lead to controlling the noise of existing helicopters by avoiding noisy regimes of flight or by redesigning the main and tail rotors The present investigation is concerned with approaches which are suitable for the calculation of discrete frequency noise of helicopter rotors The governing differential equation of acoustics used in a consideration of acoustic formulations is the Ffowcs Williams-Hawkings (FW-H) equation Attention is given to a method reported by Farassat (1981), a method developed by Succi (1979), and a procedure discussed by Woan and Gregorek (1978)
326 citations
TL;DR: Early cry and the later vocalizations of cooing and babbling appear to be vocal performances in continuity, from a strictly acoustic perspective.
Abstract: Recordings were obtained of the comfort‐state vocalizations of infants at 3, 6, and 9 months of age during a session of play and vocal interaction with the infant’s mother and the experimenter. Acoustic analysis, primarily spectrography, was used to determine utterance durations, formant frequencies of vocalic utterances, patterns of f0 frequency change during vocalizations, variations in source excitation of the vocal tract, and general properties of the utterances. Most utterances had durations of less than 400 ms although occasional sounds lasted 2 s or more. An increase in the ranges of both the F1 and F2 frequencies was observed across both periods of age increase, but the center of the F1–F2 plot for the group vowels appeared to change very little. Phonatory characteristics were at least generally compatible with published descriptions of infant cry. The f0 frequency averaged 445 Hz for 3‐month‐olds, 450 Hz for 6‐month‐olds, and 415 Hz for 9‐month‐olds. As has been previously reported for infant cry, the vocalizations frequently were associated with tremor (vibrato), harmonic doubling, abrupt f0 shift, vocal fry (or roll), and noise segments. Thus, from a strictly acoustic perspective, early cry and the later vocalizations of cooing and babbling appear to be vocal performances in continuity. Implications of the acoustic analyses are discussed for phonetic development and speech acquisition.
288 citations
TL;DR: It is shown here with simulated community data that ordi- nation selectively recovers patterns affecting several species simultaneously in early ordination axes, while selectively deferring noise to late axes, which helps to explain the observation that ordinations of field data are frequently useful even when the percentage of variance accounted for by the first few Ordination axes is small.
Abstract: Field data on the species content of plant and animal communities are noisy. Variation in community samples partly reflects interesting variation in environmental and historical factors, and partly reflects random fluctuations in species abundances. Routinely community data are analyzed by eigenvector ordination techniques, such as principal components analysis, reciprocal averaging, and detrended correspondence analysis. It is shown here with simulated community data that ordi- nation selectively recovers patterns affecting several species simultaneously in early ordination axes, while selectively deferring noise to late axes. Eigenvector ordinations thus appear to be effective for reducing noise. This result helps to explain the observation that ordinations of field data are frequently useful even when the percentage of variance accounted for by the first few ordination axes is small. A related conclusion is that rounding of the abundance values of community data sets has little effect on results from ordination, and consequently fairly crude field data are entirely adequate for ordination purposes.
248 citations
TL;DR: Increased temporal difference limen and longer gap‐detection thresholds were found to correlate significantly with reduced speech intelligibility in noise, even when the effects of the pure‐tone threshold loss were partialed out.
Abstract: Four measures of auditory temporal processing were obtained from 16 normals and 16 individuals with a hearing loss of heterogeneous origin. These measures were: (1) temporal integration—the difference in detection thresholds between signals of 10‐ and 1000‐ms duration (which was determined to provide an estimate of the ability to integrate energy over time), (2) gap detection—the shortest duration of silence between two noise bursts that can be discriminated from an uninterrupted noise, (3) temporal difference limen—the increment in duration necessary to detect a difference in the duration of a noise burst, (4) gap difference limen—the increment in duration necessary to detect a difference in the duration of a silent interval between two noise bursts. Each measure was obtained for stimuli centered both at 500 and at 4000 Hz using a three‐alternative forced‐choice procedure. In addition, measures of identification and discrimination were obtained for two sets of synthetic speech syllables varying chiefly in a temporal parameter, voice‐onset‐time, from /ba/ to /pa/ and from /bi/ to /pi/. Finally, speech identification in noise was measured with the FAAF test. Most of the hearing‐impaired listeners displayed poorer temporal analysis than the normals on all of the psychoacoustical tasks, regardless of whether the two groups were compared at similar sound pressure levels or at similar sensation levels. Although the hearing‐impaired listeners displayed a reduction in the ability to discriminate subphonemic cues for the voiced–voiceless distinction, their identification of that distinction in stop consonants appeared to be normal. The hearing‐impaired group made about twice as many errors as did the normals on each of the consonant features of place, manner, and voicing when identifying speech in noise. Increased temporal difference limen and longer gap‐detection thresholds were found to correlate significantly with reduced speech intelligibility in noise, even when the effects of the pure‐tone threshold loss were partialed out.
234 citations
TL;DR: In this paper, a brief review of the formulation of the finite element method for structural-acoustic analysis of an enclosed cavity, and illustrations are given of the application of this analytical method at General Motors Corporation to investigate the acoustics of the automobile passenger compartment.
232 citations
TL;DR: The spatial parameters that describe the visual detection of spatio-temporal correlation in moving two-dimensional noise patterns were determined and the span of the elementary correlators rose monotonically with the velocity to which the correlator is most sensitive.
Abstract: We obtained movement detection thresholds for two-dimensional random speck-patterns ("Julesz" patterns) homogeneously moving over the whole target field (5.21 x 5.31 degrees of visual angle). We alternated between two uncorrelated but otherwise similar patterns, one moving with velocity leads to V1, the other with velocity leads to V2, such that each pattern was on for T ms. We masked this pattern (signal) with spatio-temporal white noise ("snow"). The total r.m.s. contrast was kept constant, whereas the ration of the r.m.s. contrasts of signal and noise was varied. The square of this ratio was designated SNR. At low SNR values the pattern was not perceptually different from the snow alone. At high SNR values the subject detected spatio-temporal correlation (e.g., movement). In these experiments we determined the threshold SNR values as a measure of the detectability of spatio-temporal correlation as a function of the parameters T, leads to V1, and leads to V2. When leads to V1 and leads to V2 were sufficiently dissimilar one of three percepts occurred: for very large T the alternation could be followed, for very small T two transparent, simultaneously moving sheets of noise-pattern with different velocities could be seen. For intermediate T-values no systematic movement at all could be observed. At these T-values the threshold SNR was maximal. This "'critical" T-value decreased with increasing velocity. We found that it was possible to have more than one percept of uniform smooth movement at a single location in the visual field if these movements had velocity vectors with an angular difference of at least 30 deg or if their magnitudes differed by at least a factor of 4.
01 Sep 1982
TL;DR: In this article, the autoregressive coefficients are themselves estimated robustly in an iterative loop along with the data-cleaning operation, and the well-cleaned data are then used along with a smoothed spectral density estimate via prewhitening.
Abstract: Conventional spectrum estimates of both the smoothed-periodogram and autoregressive variety lack robustness toward outliers in the original data. Outliers and other local perturbations are modeled by non-Gaussian additive noise, which is zero most of the time. Correspondingly, the lack of robustness of the conventional estimates of the spectrum manifest not only inflated variances but also damaging asymptotic biases. This paper discusses robust-resistant methods of spectrum estimation which do not suffer in this way. The main approach involves "data cleaning" by either one-sided or two-sided outlier interpolators based on autoregressive approximations. The autoregressive coefficients are themselves estimated robustly in an iterative loop along with the data-cleaning operation. The well-cleaned data are then used along with the autoregressive model to form smoothed spectral density estimates via prewhitening. Study of the so-called "linear part" of the nonlinear outlier interpolator algorithm shows that considerable bias reduction is realizable through use of the robust procedure. Some examples of applications of the robust methodology are presented. Special considerations for real-time processing and large data sets are discussed. Extensions of the method to cross-spectrum estimation, missing data, and irregularly spaced data problems are briefly mentioned.
TL;DR: The noise response of switched capacitor networks is reviewed with emphasis on simplifying approximations suitable for SPICE noise simulation, which shows close agreement between predicted and measured noise responses for several monolithic SCNs.
Abstract: The noise response of switched capacitor networks (SCNs) is reviewed with emphasis on simplifying approximations suitable for SPICE noise simulation. The techniques developed cover all op-amp noise sources, as well as capacitor switching noise. The close agreement between predicted and measured noise responses for several monolithic SCNs bears out the validity of these simulation techniques.
01 Feb 1982
TL;DR: The prediction of data which affect noise generation and propagation is addressed, including the aircraft flight dynamics, the source noise parameters, and the propagation effects.
Abstract: Detailed prediction methods for specific aircraft noise sources are given. These sources are airframe noise, combustion noise, fan noise, single and dual stream jet noise, and turbine noise. Modifications to the NASA methods which comply with the International Civil Aviation Organization standard method for aircraft noise prediction are given.
Journal Article•
TL;DR: In this paper, the authors reviewed nine empirical studies of highway noise and property values, conducted since 1974, using cross-sectional housing data concerning cities in Canada and the USA, and concluded that highway noise does not lead to delays in selling property and should not therefore reduce residential mobility.
Abstract: The paper critically reviews nine empirical studies of highway noise and property values. These studies, conducted since 1974, use cross-sectional housing data concerning cities in Canada and the USA. A number of assumptions that underlie the price model are discussed, and also highway noise measurement fundamentals are reviewed. The results of the surveys are summarised in the form of a noise depreciation sensitivity index which is the ratio of the price of quiet to the price of an average property. The range of values for this index provides a means of evaluating the consistency of the studies and of their results. Empirical studies received employ a variey of traffic noise measures and model specifications. The evidence reviewed suggests that highway noise does not lead to delays in selling property and should not therefore reduce residential mobility. (Author/TRRL)
TL;DR: The authors examined reactions to traffic noise from the opening of a major new highway and found no evidence of appreciable adaptation in self-reported noise effects, annoyance, or tendency to focus attention on the noise.
TL;DR: In this paper, the authors investigated the accuracy of the compensated least squares (CLS) method and proved that the estimates are asymptotically gaussian distributed. And they also showed that a commonly used instrumental variable method gives a better accuracy than the CLS method.
Abstract: The least-squares method in system identification leads generally to biased parameter estimates. A conceptually simple modification is to estimate the bias and to compute compensated parameter estimates. When white output noise is the only disturbance this principle (compensated least squares, CLS) can readily be used to obtain consistent estimates. The main purpose of the paper is to investigate the accuracy of the parameter estimates obtained when the CLS method is used. It is proved that the estimates are asymptotically gaussian distributed. An explicit expression for the covariance matrix is given. It is also shown that a commonly used instrumental variable method gives (asymptotically) better accuracy than the compensated least-squares method.
TL;DR: In this paper, an adaptable waveform generator, an electro-acoustic transducer, and an adaptor are used to improve the audibility of incident sound to a person operating in an environment where there is a substantial background noise field coming from a source of repetitive noise.
Abstract: Apparatus for improving the audibility of incident sound (4) to a person (3) operating in an environment where there is a substantial background noise field (2) coming from a source (1) of repetitive noise, comprises an adaptable waveform generator (7), a first electro-acoustic transducer (10) receiving a synthesized cancelling waveform from the generator (7) and generating a cancelling noise to at least partly null the background noise, a second electro-acoustic transducer (11) to sense the partially nulled background noise, and adaptor (13) to modify the output of the generator (7) on the basis of the electrical output signal from the second transducer to minimize the nulled background noise, and sensor (5) to feed a triggering signal (6) derived from the source to the waveform generator. The electro-acoustic transducers (10, 11) can be mounted in headset (8) holding the transducers adjacent to an ear of said person without substantially impeding the arrival of said incident sound (4) to said ear.
TL;DR: A minimum cost capacitated network flow algorithm is discussed, which yields the optimal solution with respect to the priori information, and is shown that this method can also be used in the presence of observation noise.
TL;DR: In this paper, the properties of correlated double sampling techniques are discussed in detail and the relative merits of each scheme depend on the exact nature of the noise sources and the relationship between output noise and such parameters as signal integration time can be used to determine the noise spectrum.
Abstract: The properties of several widely used CCD signal-processing schemes are discussed in detail. A common feature is that correlated double sampling techniques are used to attenuate low frequency noise. The relative merits of each scheme depend on the exact nature of the noise sources. Formulae are derived which enable assessment of the best scheme to use for a particular device once its noise spectrum is konwn; conversely, the relationship between output noise and such parameters as signal integration time can be used to determine the noise spectrum. The analysis also applies to charge injection devices and voltage sampling diode arrays. For each scheme the formulae are used to predict the readout noise for a system employing a cooled GEC MA328 CCD.
TL;DR: Data analysis suggests that the extent of the increments and decrements in perceived magnitude depends on the absolute loudness of the component stimuli, the interaction between a specific tone frequency and noise spectrum, and the attribute judged.
Abstract: Single tones centered within the noise spectrum were added to three different broadband spectra: flat, low pass, and high pass. Judgments of overall loudness, annoyance, and noisiness (perceived magnitude) were obtained by absolute magnitude estimation (AME) supplemented by loudness matching. The data were evaluated to determine how the overall SPL of the noise‐tone complex, and tone‐to‐noise ratio affect judged perceived magnitude. In addition, the relationship among the three judged attributes was assessed. Results obtained with the different noise spectra show that the growth of perceived magnitude is a nonmonotonic function of the overall SPL of the noise‐tone complex. More summation between tone and noise was found for relatively small tone‐ to‐noise ratios (+5, +10, +15 dB), as measured in 1/3‐octave bands, than for relatively large tone‐to‐noise ratios (+20 dB and greater). Data analysis suggests that the extent of the increments and decrements in perceived magnitude depends on the absolute loudnesses of the component stimuli, the interaction between a specific tone frequency and noise spectrum, and the attribute judged. An attempt is made to quantify the observed effects and to relate them to the published results of other investigators.
TL;DR: A reconstruction algorithm for TOF-positron computed tomography (PCT) based on the back-projection with 1-dimensional weight and 2-dimensional filtering is presented and a formula to evaluate the variance of the reconstructed image and the optimal back- projection function are presented.
Abstract: In positron CT, the path difference of annhilation pair gamma rays can be measured by time-of-flight (TOF) difference of pair gamma rays. This TOF information gives us rough position information along a projection line and will reduce noise propagation in the reconstruction process. A reconstruction algorithm for TOF-positron computed tomography (PCT) based on the back-projection with 1-dimensional weight and 2-dimensional filtering is presented. Also a formula to evaluate the variance of the reconstructed image and the optimal back-projection function are presented. The advantage of TOF-PCT over conventional PCT was investigated in view of noise figure. An example of such noise figure evaluations for CsF and liquid Xenon scintillators is given.
TL;DR: Novel experimental data is reported for an all-fiber gyroscope with a noise density of 0.004(deg/h)(2)/Hz compatible with the requirements for inertial navigation.
Abstract: We report new experimental data for an all-fiber gyroscope with a noise density of 0.004(deg/h)2/Hz. This is compatible with the requirements for inertial navigation. Noise contributions from the coherent Rayleigh backscatter when a phase-modulation bias scheme is used and also from acoustic vibrations are discussed.
TL;DR: In this article, a system for the active acoustic attenuation of noise produced in the interior of an enclosure by a source of noise is presented, which in one aspect comprises input sensing operable to sense the source noise to be attenuated, cancellor adapted to produce noise 180° out of phase with the source noises and error sensor operable for sense the acoustic summation of the noise and the noise produced by the cancellor.
Abstract: This invention is directed to a system for the active acoustic attenuation of noise produced in the interior of an enclosure by a source of noise which in one aspect comprises input sensing operable to sense the source noise to be attenuated, cancellor adapted to produce noise 180° out of phase with the source noise and error sensor operable to sense the acoustic summation of the source noise and the noise produced by the cancellor. The input sensor, cancellor and error sensor are each preferably disposed at or immediately adjacent an area of high acoustic pressure within the enclosure. The system further includes a second input sensor disposed adjacent the source of noise, a second cancellor adapted to introduce noise 180° out of phase with the source noise at a location at or immediately adjacent the enclosure wall and second error sensor disposed in the interior of the enclosure. Each set of input sensing means, cancellor and error sensor are adapted to be connected to an electronic controller means operable to process signals from the input sensor, produce outputs to drive the cancellor for the introduction of cancelling sound waves into the enclosure for combination with the source sound waves, and then adjust such outputs based on signals received from the error sensor.
TL;DR: In this article, the authors compared the performance of conventional and nearly optimum signal processing methods using FRAM II data in the Canadian Arctic Archipelago and reported that the ability to detect and estimate signals contaminated with non-Gaussian noise using conventional processing is degraded compared with optimum techniques which utilize knowledge of the noise statistics.
Abstract: Recent analyses of FRAM II arctic data have shown that under ice ambient noise can be at times highly impulsive and non‐Gaussian. The analyses included time domain statistical measurements which were consistent with previously reported results of experiments made within the Canadian Arctic Archipelago. New findings in the frequency domain based on skew, kurtosis, and cumulative distribution function estimates, also indicate the existence of strong non‐Gaussian noise. It is known that the ability to detect and estimate signals contaminated with non‐Gaussian noise using conventional processing is degraded compared with optimum techniques which utilize knowledge of the noise statistics. Results comparing the performance of conventional and nearly optimum signal processing methods are presented using the FRAM II data.
TL;DR: The effects of railway noise on residents have been measured with a combined social survey (1453 respondents) and noise measurement survey (over 2000 noise measurements) at 403 locations in 75 study areas in Great Britain this paper.
Patent•
29 Apr 1982
TL;DR: In this article, a two-way (interactive) cable television system is described, which employs a cable-distribution subsystem that includes corrective regenerators each of which ignores noise (invalid signals) and, when overloaded, ignores (rejects) certain valid signals so as to favor older information (commands).
Abstract: A two-way (interactive) cable television system is disclosed which has distributed processing and which employs a cable-distribution subsystem that includes corrective regenerators each of which ignores noise (invalid signals) and, when overloaded, ignores (rejects) certain valid signals so as to favor older information (commands).
TL;DR: In this article, the authors derived a formula for the high frequency sound emission from moving point multipole sources embedded in an arbitrary unidirectional transversely sheared mean flow.