Showing papers on "Noise published in 1981"
TL;DR: This paper develops a statistical technique to define a noise model, and then successfully applies a local statistics noise filtering algorithm to a set of actual SEASAT SAR images, resulting in smoothed images that permit observers to resolve fine detail with an enhanced edge effect.
880 citations
TL;DR: In this paper, the Bode magnitude versus frequency plots of the singular values of the return difference matrix I + L and of the associated inverse-return difference were quantitatively described and design tradeoffs were discussed.
Abstract: For linear time-invariant multivariable feedback systems, the feedback properties of plant disturbance attenuation, sensor noise response, stability margins, and sensitivity to plant and sensor variation are quantitatively related to the Bode magnitude versus frequency plots of the singular values of the return difference matrix I + L and of the associated inverse-return difference matrix I + L^{-1} . Implied fundamental limits of feedback performance are quantitatively described and design tradeoffs are discussed. The penalty function in the stochastic linear quadratic Gaussian (LQG) optimal control problem is found to be a weighted-sum of the singular values, with the weights determined by the quadratic cost and noise intensity matrices. This enables systematic "tuning" of LQG cost and noise matrices so that the resulting optimal return difference and inversereturn difference meet inequality constraints derived from design specifications on feedback properties. The theory has been used to synthesize a multivariable automatic controller for the longitudinal dynamics of an advanced fighter aircraft.
550 citations
TL;DR: The overall statistical efficiency of human subjects discriminating the amplitude of visual pattern signals added to noisy backgrounds is measured by changing the noise amplitude, and the amount of intrinsic noise can be estimated and allowed for.
Abstract: We have measured the overall statistical efficiency of human subjects discriminating the amplitude of visual pattern signals added to noisy backgrounds. By changing the noise amplitude, the amount of intrinsic noise can be estimated and allowed for. For a target containing a few cycles of a spatial sinusoid of about 5 cycles per degree, the overall statistical efficiency is as high as 0.7 +/- 0.07, and after correction for intrinsic noise, efficiency reaches 0.83 +/- 0.15. Such a high figure leaves little room for residual inefficiencies in the neural mechanisms that handle these patterns.
435 citations
TL;DR: In this paper, a unified approach is used to derive many of the current formulas for calculation of discrete frequency noise of helicopter rotors and propellers, both compact and non-compact results are derived.
Abstract: A unified approach is used to derive many of the current formulas for calculation of discrete frequency noise of helicopter rotors and propellers. Both compact and noncompact results are derived. The noncompact results are based on the solution of Ffowcs Williams-Hawkings (FW-H) equation. The compact formulations are obtained as the limit of noncompact source results. In particular, the linearized acoustic theories of Hawkings and Lowson, Farassat, Hanson, Woan and Gregorek, Succi, and Jou are discussed in this paper. An interesting thickness noise formula by Isom and its extension by Ffowcs Williams are also presented.
333 citations
TL;DR: In this paper, the estimation of time delays between two received signals using phase measurements is discussed and the accuracy of such estimates is detailed for the ideal case of statistically independent noise and no scattering at the receiver locations, it is shown that phase data regression lines yield time delay estimates with the same accuracy as other optimal time delay estimation procedures.
Abstract: The estimation of time delays between two received signals using phase measurements is discussed and the accuracy of such estimates is detailed. For the ideal case of statistically independent noise and no scattering at the receiver locations, it is shown that phase data regression lines yield time delay estimates with the same accuracy as other optimal time delay estimation procedures. For less ideal situations, the potential advantages of time delay estimation using phase data are discussed and illustrated. It is shown that regression analysis of phase estimates at properly selected frequencies can sometimes be employed to reduce bias errors in time delay estimates due to correlated receiver noise. It is also shown that the estimation errors due to scattering at the receiver location can often be assessed in nonparametric terms to provide time delay estimates with a realistic error bound.
240 citations
Book•
01 Jan 1981
TL;DR: In this paper, the authors present an overview of the basic foundations of sound, including the ear and the perception of sound and sound levels and the decibel, as well as a discussion of the effects of noise in the listening and control rooms.
Abstract: 1. Fundamentals of Sound 2. Sound Levels and the Decibel 3. The Ear and the Perception of Sound 4. Sound Waves in the Free Field 5. Speech, Music, and Noise 6. Analog and Digital Signal Processing 7. Reverberation 8. Control of Interfering Noise 9. Absorption of Sound 10. Reflection of Sound 11. Diffraction of Sound 12. Refraction of Sound 13. Diffusion of Sound 14. The Shroeder Diffusor 15. Modal Resonances in Enclosed Spaces 16. Reflections in Enclosed Spaces 17. Comb-filter Effects 18. Quiet Air for the Studio 19. Acoustics of the Listening Room 20. Acoustics of the Small Recording Studio 21. Acoustics of the Control Room 22. Acoustics for Multi-Track Recording 23. Audio/Video Tech Room for Voice-over Recording 24. Adjustable Acoustics 25. Acoustical Measurements and Calculations Appendices
207 citations
01 Dec 1981
TL;DR: Describes the implementation of a wide dynamic range voiceband switched-capacitor filter using a differential chopper-stabilized configuration and experimental results from a fifth-order low-pass voiceband prototype are presented.
Abstract: Describes the implementation of a wide dynamic range voiceband switched-capacitor filter using a differential chopper-stabilized configuration. The noise behavior of switched-capacitor filters is discussed qualitatively, and the effects of the chopper stabilization on the noise performance is analyzed. Experimental results from a fifth-order low-pass voiceband prototype are presented.
206 citations
TL;DR: In this paper, the effects of noise on human performance, interpersonal behavior, annoyance, cognitive development, and mental and physical health are reviewed, and the relevance of this research for predicting the effect of noise in community and industrial settings is emphasized.
Abstract: This article presents an overview of research and theory on the nonauditory effects of noise on human behavior and health. Laboratory and naturalistic research on the effects of noise on human performance, interpersonal behavior, annoyance, cognitive development, and mental and physical health are reviewed. The review includes studies of children as well as adults, and the discussion emphasizes the relevance of this research for predicting the effect of noise in community and industrial settings. Noise effects are viewed as determined by variations in psychological characteristics of a situation as well as the physical parameters of the sound. Predictability and controllability of a noise, its meaning for the respondent and its degree of interference with auditory communication are factors that mediate the effects of noise across a variety of outcome measures.
186 citations
TL;DR: The theory of tomographical imaging with limited angular input, from which two reconstruction algorithms are derived, is discussed in this article, where the existence of missing information because of incomplete angular coverage is demonstrated, and an iteration algorithm to recover this information from a priori knowledge of the finite extent of the object is developed.
Abstract: The theory of tomographical imaging with limited angular input, from which two reconstruction algorithms are derived, is discussed. The existence of missing information because of incomplete angular coverage is demonstrated, and an iteration algorithm to recover this information from a priori knowledge of the finite extent of the object is developed. Smoothing algorithms to stabilize reconstructions in the presence of noise are given. The effects of digitization and finite truncation of the reconstruction region in numerical computation are also analyzed. It is shown that the limited-angle problem is governed by a set of eigenvalues whose spectrum is determined by the imaging angle and the finite extent of the object. The distortion on a point source caused by the missing information is calculated; from the results some properties of the iteration scheme, such as spatial uniformity, are derived.
176 citations
01 Nov 1981
TL;DR: In this paper, a two dimensional section of a helicopter main rotor blade was tested in an acoustic wind tunnel at close to full-scale Reynolds numbers to obtain boundary layer data and acoustic data for use in developing an acoustic scaling law and testing a first principles trailing edge noise theory.
Abstract: A two dimensional section of a helicopter main rotor blade was tested in an acoustic wind tunnel at close to full-scale Reynolds numbers to obtain boundary layer data and acoustic data for use in developing an acoustic scaling law and testing a first principles trailing edge noise theory. Results were extended to the rotating frame coordinate system to develop a helicopter rotor trailing edge noise prediction. Comparisons of the calculated noise levels with helicopter flyover spectra demonstrate that trailing edge noise contributes significantly to the total helicopter noise spectrum at high frequencies. This noise mechanism is expected to control the minimum rotor noise. In the case of noise radiation from a local blade segment, the acoustic directivity pattern is predicted by the first principles trailing edge noise theory. Acoustic spectra are predicted by a scaling law which includes Mach number, boundary layer thickness and observer position. Spectrum shape and sound pressure level are also predicted by the first principles theory but the analysis does not predict the Strouhal value identifying the spectrum peak.
174 citations
TL;DR: In this article, the authors measured self-generated electrochemical potential fluctuations on electrodes undergoing either pitting or crevice corrosion and found that these forms of localized attack have quite distinct noise signatures.
TL;DR: In this article, a reconstruction algorithm for TOF-positron computed tomography (PCT) based on the back-projection with 1-dimensional weight and 2-dimensional filtering is 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: It is hypothesized that perceptual effects of the fricative context effect serve to compensate for coarticulatory dependencies between stop consonants and preceding fricatives.
Abstract: The effect of a preceding fricative on the perceived place of stop consonant articulation was investigated in a series of experiments. In experiment 1, we preceded synthetic syllables from two [tV]–[kV] continua with fricative noises appropriate to [F] or [s] and showed that more velar stops are perceived in the context of [s]. Experiment 1 also demonstrated a decrease in the magnitude of this perceptual context effect with increased temporal separation of fricative noise and CV portion, and with introduction of a vowel before the noise, which permitted a subjective syllable boundary after the fricative. Experiment 2 showed that although the effect of the fricative on stop perception declines initially with temporal separation, it may persist in reduced form over intervals as long as 375 ms. Experiment 3 replicated the basic fricative context effect using improved stimuli, but failed to replicate the reduction with an intervening syllable boundary obtained in experiment 1, which presumably was due to the ...
TL;DR: A Hilbert space approach to the derivations of magnitude normalized signal and gain recursions is presented and normalized forms are expected to have even better numerical properties than the unnormalized versions.
Abstract: Recursive least squares ladder estimation algorithms have attracted much attention recently because of their excellent convergence behavior and fast parameter tracking capability, compared to gradient based algorithms. We present some recently developed square root normalized exact least squares ladder form algorithms that have fewer storage requirements, and lower computational requirements than the unnormalized ones. A Hilbert space approach to the derivations of magnitude normalized signal and gain recursions is presented. The normalized forms are expected to have even better numerical properties than the unnormalized versions. Other normalized forms, such as joint process estimators (e.g., "adaptive line enhancer") and ARMA (pole-zero) models, will also be presented. Applications of these algorithms to fast (or "zero") startup equalizers, adaptive noise- and echo cancellers, non-Gaussian event detectors, and inverse models for control problems are also mentioned.
TL;DR: Burns and Viemeister as discussed by the authors showed that the pitch-like sensation elicited by sinusoidally amplitude-modulated (SAM) noise can be mediated by short-term spectral information rather than temporal information.
Abstract: The pitchlike sensation elicited by sinusoidally amplitude‐modulated (SAM) noise remains a controversial phenomenon. The controversy centers on two major points: (1) whether this sensation is ’’really’’ pitch rather than, e.g., roughness or intermittency, and (2) the possibility that any pitch sensation is mediated by short‐term spectral information rather than temporal information—thus nullifying an interesting aspect of the phenomenon. Three experiments employing SAM wideband noise, SAM wideband noise bandpass‐filtered after modulation, and a SAM 10 kHz pure tone were performed: (1) open‐set melody identification, (2) melodic dictation, and (3) musical‐interval adjustment. These experiments extend our earlier study [Burns and Viemeister, J. Acoust. Soc. Am. 60, 863 (1976)]. The results provide further evidence that SAM noise can, at suitable modulation frequencies, elicit a sensation of pitch (as defined by the ability to carry melodic information), and that this pitch represents a purely temporal phenomenon.
TL;DR: The thesis of this paper is that research upon, and efforts to prevent or minimize the harmful effects of noise have suffered from the lack of a full appreciation of the ways in which humans process and react to sound.
Abstract: The fundamental purposes of hearing are to alert and to warn. As a result sound directly evokes emotions and actions. The processing of sound by the brain is outlined to provide a biological and psychological basis for understanding the way in which sound can become a human stressor. The auditory orienting response, startle reflex and defensive response translate sound stimuli into action and sometimes into stress induced bodily changes through "fight or flight" neural mechanisms. The literature on the health and mental health effects of noise then is reviewed in the context of an integrated model that offers a holistic approach to noise research and public policy formulation. The thesis of this paper is that research upon, and efforts to prevent or minimize the harmful effects of noise have suffered from the lack of a full appreciation of the ways in which humans process and react to sound.
TL;DR: In two-dimensional image reconstruction from line integrals using maximum likelihood, Bayesian, or minimum variance algorithms, the x-y plane on which the object estimate is defined is decomposed into nonoverlapping regions, or "pixels".
Abstract: In two-dimensional image reconstruction from line integrals using maximum likelihood, Bayesian, or minimum variance algorithms, the x-y plane on which the object estimate is defined is decomposed into nonoverlapping regions, or "pixels." This decomposition of an otherwise continuous structure results in significant errors, or model noise, which can exceed the effects of the fundamental measurement noise.
TL;DR: In this article, the authors developed an intuitive understanding of the meaning and implications of Middleton's canonical formula for Class A noise and derived the probability density function for noise in decibels.
Abstract: This paper develops an intuitive understanding of the meaning and implications of Middleton's canonical formula for Class A noise. The probability density function (pdf) for noise in decibels is derived, and each of the parameters has a clear physical meaning. The effects of parameter variation on the pdf are shown graphically. The canonical Class A formula predicts that the interdecile range of non- Gaussian noise (structured interference) is less than about 30 dB. A simple scenario that produces canonical Class A interference is described. The limited interdecile range of the interference forces the interfering sources in the simple scenario to be located within a limited range of distances. Thus the strictly canonical formula for Class A noise is inadequate for modeling many physical situations.
TL;DR: In this paper, longitudinal and cross-sectional data on effects of aircraft noise on elementary school children are presented as evidence for the effects of community noise on behavior, including attentional strategies, learned helplessness, performance on cognitive tasks, and blood pressure.
Abstract: Longitudinal and cross-sectional data on effects of aircraft noise on elementary school children are presented as evidence for the effects of community noise on behavior. To examine the generality of previous laboratory findings in a naturalistic setting, the study assesses the impact of noise on attentional strategies, learned helplessness, performance on cognitive tasks, and blood pressure. Children were tested on the same measures twice, with a 1-year interval between sessions. A previous article reported cross-sectional findings from the first testing session. In the present article, longitudinal data are used to determine whether children adapt to the aircraft noise over the 1-year period and to assess the effectiveness of noise abatement interventions introduced in a number of noiseimpacted classrooms. Additional cross-sectional data from the original testing session are also presented to provide further information on the utility of noise abatement. In general, there was little evidence for adaption to noise over the 1-year period. Noise abatement had small ameliorative effects on cognitive performance, children's ability to hear their teachers, and school achievement. The implications of the study for understanding the relationship between noise and behavior and resulting policy implications are discussed.
TL;DR: Acoustic measurements of nonsense syllables in quiet and in noise were used to predict the pattern of consonant confusions made under those conditions, and a set of acoustic variables was found to be the best predictor of confusion percentages.
Abstract: Acoustic measurements of nonsense syllables in quiet and in noise were used to predict the pattern of consonant confusions made under those conditions. Eleven sets of nonsense syllables were presented to normal‐hearing subjects in quiet and at a +5 dB speech‐to‐noise ratio, at five speech levels. A set of acoustic characteristics of the speech stimuli were chosen for analysis and measured using digital speech processing techniques. Results of the recognition task revealed significant effects of consonant voicing, position and vowel context on syllable recognition. The performance‐intensity function for the quiet condition rises more steeply than the function obtained in noise. The effect of noise on consonant recognition is dependent upon the manner in which the consonant is produced, and the location of maximum constriction. Differences in the absolute values of the acoustic parameters of syllable pairs were used to predict their percentage of confusion. A set of acoustic variables was isolated which was found to be the best predictor of confusion percentages. Although the sets of acoustic variables were different for various syllable types and test conditions, three variables (consonant energy, consonant spectral peaks, consonant‐to‐noise ratio) were used in a majority of the predictions.
TL;DR: A new formulation is proposed for the problem of parameter estimation of dynamic systems with both process and measurement noise that gives estimates that are maximum likelihood asymptotically in time.
Abstract: A new formulation is proposed for the problem of parameter estimation of dynamic systems with both process and measurement noise. The formulation gives estimates that are maximum likelihood asymptotically in time. The means used to overcome the difficulties encountered by previous formulations are discussed. It is then shown how the proposed formulation can be efficiently implemented in a computer program. A computer program using the proposed formulation is available in a form suitable for routine application. Examples with simulated and real data are given to illustrate that the program works well.
TL;DR: Results agree best with previous studies that suggest that noise may reduce prenatal growth and the size of the observed effects may be related to a conservative research design biased towards underestimation, as well as to the real effects of noise upon human prenatal growth.
Abstract: To determine whether chronic exposure to relatively loud noise has demonstrable biological effects in humans, a study was conducted on the effect of mother's exposure to airport noise while pregnant, and of social and biological characteristics of the family upon birthweight and gestation length. The sample of births was drawn from a community located adjacent to an international airport in the U.S., where noise levels had been measured previously. Mother's noise exposure was based upon noise levels near her residence in the community while she was pregnant. Data from 115 births were used, these being from mothers whose noise exposure history was most complete throughout the pregnancy. Using multivariate analysis to correct for family characteristics, the partial correlation coefficient for noise exposure and gestation length was negative, large, and significant in girls (r = -0.49, p less than 0.001). In boys the partial correlation coefficient was also negative but was smaller and did not quite reach statistical significance. Partial correlations with birthweight were smaller in both boys and girls and not significant. These results agree best with previous studies that suggest that noise may reduce prenatal growth. The size of the observed effects may be related to a conservative research design biased towards underestimation, as well as to the real effects of noise upon human prenatal growth.
TL;DR: Hearing in Classical Musicians is studied in classical musicians to find out if hearing impairment is a problem or a feature of the performance.
Abstract: (1981). Hearing in Classical Musicians. Acta Oto-Laryngologica: Vol. 91, No. sup377, pp. 1-100.
TL;DR: High-frequency (8 to 20 kHz) hearing sensitivity was compared in thirty-six, 20 to 29-year-old military veterans with histories of steady-state or impulsive noise exposure to provide for more comprehensive inter- and intra-subject comparison of the degree and extent of threshold changes present.
Abstract: High‐frequency (8 to 20 kHz) hearing sensitivity was compared in thirty‐six, 20 to 29‐year‐old military veterans with histories of steady‐state or impulsive noise exposure. Threshold shifts were prominent for the steady‐state noise subjects from 13 to 20 kHz. Mean thresholds from 8 through 12 kHz were maximally 20 dB poorer than a sample of young adult normals. Audiometric configurations for this group were generally smooth and symmetrical above 8000 Hz. For the impulsive noise group, substantial shifts in sensitivity were seen from 2 to 20 kHz and the high‐frequency audiometric configurations were often jagged and/or asymmetrical. The variability of subjects in this group was greater than that seen in the steady‐state noise exposed sample. Several case studies are presented to illustrate these characteristics. Measurement of auditory sensitivity from 8 to 20 kHz extends the mapping of basal cochlear function, providing information which often is not predictable from conventional audiometric measurement. This additional information provides for more comprehensive inter‐ and intra‐subject comparison of the degree and extent of threshold changes present.
TL;DR: In this paper, the Bonneville Power Administration's basic philosophy for predicting audible noise from ac and dc high voltage transmission lines is described, and general formulas for predicting the A-weighted audible noise during rain for ac lines and during fair weather for dc lines which were developed from data from full scale lines are presented.
Abstract: This paper describes Bonneville Power Administration's basic philosophy for predicting audible noise from ac and dc high voltage transmission lines. General formulas for predicting the A-weighted audible noise during rain for ac lines and during fair weather for dc lines which were developed from data from full-scale lines are presented. From this basic calculation, audible noise cumulative distributions, frequency spectrums, and lateral profiles can be estimated
TL;DR: The detectability of a sinusoidal grating was measured in a standard two-interval forced-choice experiment against backgrounds of noise gratings of the same orientation as the signal.
Abstract: The detectability of a sinusoidal grating was measured in a standard two-interval forced-choice experiment against backgrounds of noise gratings of the same orientation as the signal. The noise gratings were either spatially high-pass or low-pass filtered and were either unchanged in each observation interval (static) or flickering at a rate that depended on their cutoff frequency (dynamic). Spatial-frequency-selective mechanisms are inferred from the data and their characteristics shown to depend on assumptions concerning the detection process thought to follow the spatial-frequency-selective device.
TL;DR: Patients who complain of hearing difficulty should be examined and their hearing tested to determine hearing acuity, speech reception threshold, and speech discrimination as well as whether amplification is warranted.
Abstract: Audiology is an essential aid to diagnosis of hearing loss, including loss due to exposure to excessive noise. Patients who complain of hearing difficulty should be examined and their hearing tested to determine hearing acuity, speech reception threshold, and speech discrimination as well as whether amplification is warranted.