Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “loudness”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Infrared observations of Seyfert galaxies and quasars

The infrared energy distributions of the Seyfert galaxies apparently contain three components: a galactic stellar component, a thermal component from heated dust, plus a nonthermal component. The appearance of the infrared energy distribution depends on which component dominates. There is also a correlation observed between the infrared energy distribution and the Khachikian Weedman class. Preliminary data on bright quasars are given. The infrared energy distributions generally increase into the infrared with a power law slope of approximately 1. In detail they differ from power laws with a significant fraction emitting most of their energy near 3 micrometers. No differences in radio loud and radio quiet are obvious from the infrared energy distributions. The variability of the quasars in the infrared is generally correlated with the variability in the visible, although significant exceptions have been observed.

Neugebauer, G.↗
NASA NTRS1979

Effect of grazing flow on the acoustic impedance of Helmholtz resonators consisting of single and clustered orifices

A semiempirical fluid mechanical model is derived for the acoustic behavior of thin-walled single orifice Helmholtz resonators in a grazing flow environment. The incident and cavity sound fields are connected in terms of an orifice discharge coefficient whose values are determined experimentally using the two-microphone method. Measurements show that at high grazing flow speeds, acoustical resistance is almost linearly proportional to the grazing flow speed and almost independent of incident sound pressure. The corresponding values of reactance are much smaller and tend towards zero. For thicker-walled orifice plates, resistance and reactance were observed to be less sensitive to grazing flow as the ratio of plate thickness to orifice diameter increased. Loud tones were observed to radiate from a single orifice Helmholtz resonator due to interaction between the grazing flow shear layer and the resonator cavity. Measurements showed that the tones radiated at a Strouhal number equal to 0.26. The effects of grazing flow on the impedance of Helmholtz resonators consisting of clusters of orifices was also studied. In general, both resistance and reaction were found to be virtually independent of orifice relative spacing and number. These findings are valid with and without grazing flow.

Hersch, A. S.↗
NASA NTRS1980

Another look at aircraft-triggered lightning

There is positive evidence that a rapidly moving aircraft charged to high potentials by triboelectric processes can trigger lightning discharges by passage through freezing precipitation. The freezing zone in a nonstormy rain cloud is shown to be an electrically volatile region because of the potent charge exchange mechanisms which are active in agitated mixtures of supercooled water droplet and ice. Several intensifying effects are suggested which can be produced by the passage of an aircraft through this precipitation, resulting in a highly-ionized wake which acts like a trailing conductor. If weak charge centers are present in the cloud, the ionized wake acts to short out the gradient field resulting in very high potentials at the aircraft. The high potentials explain the electrical activity at the aircraft described by pilots, including intense corona, sparks and radio interference terminating in a loud discharge. Lightning strikes to naval aircraft towing gunnery targets at the end of long steel cables are described, showing that the same triggering mechanism may be involved in those cases. Recommendations are made to include triggering experiments in government flight programs now in progress.

Clifford, D. W.↗
NASA NTRS1980

A study of poultry processing plant noise characteristics and potential noise control techniques

The noise environment in a typical poultry processing plant was characterized by developing noise contours for two representative plants: Central Soya of Athens, Inc., Athens, Georgia, and Tip Top Poultry, Inc., Marietta, Georgia. Contour information was restricted to the evisceration are of both plants because nearly 60 percent of all process employees are stationed in this area during a normal work shift. Both plant evisceration areas were composed of tile walls, sheet metal ceilings, and concrete floors. Processing was performed in an assembly-line fashion in which the birds travel through the area on overhead shackles while personnel remain at fixed stations. Processing machinery was present throughout the area. In general, the poultry processing noise problem is the result of loud sources and reflective surfaces. Within the evisceration area, it can be concluded that only a few major sources (lung guns, a chiller component, and hock cutters) are responsible for essentially all direct and reverberant sound pressure levels currently observed during normal operations. Consequently, any effort to reduce the noise problem must first address the sound power output of these sources and/or the absorptive qualitities of the room.

Wyvill, J. C.↗
NASA NTRS1980

Spectroscopy of compact extragalactic X-ray sources

The X-ray spectra of compact extragalactic sources obtained from the HEAO-1 A-2 experiment and the solid-state spectrometer onboard HEAO-2 (the Einstein Observatory) are reviewed. Seyfert spectra are remarkably consistent with characteristic power-law spectra of energy index alpha = 0.7 + .1 over a dynamic range of almost 100 in both luminosity for the whole sample, and energy for individual members. Radio-quiet quasars have similar spectra, perhaps slightly steeper, for the limited sample available. New solid-state spectrometer results for NGC 4151 yield a consistent picture for the geometry of the broad-line clouds in both these related radio-quiet classes of galactic nuclei. Radio-loud objects, especially BL Lacs, are considerably more variable in spectrum as well as luminosity. Direct synchrotron and synchrotron-self-Compton components are consistent with what we observe from these objects. Finally, the role of spectroscopy in addressing the extent to which compact extragalactic nuclei might contribute to the diffuse X-ray background is discussed.

Holt, S. S.↗
NASA NTRS1980

The effects of cognitive and behavioral control on post-stress performance

A study was designed to investigate the effects of behavioral and cognitive control on post-stress performance. Half of the subjects exposed to loud unpredictable noise bursts were given 'behavioral' control (a button which would terminate the noise), while the other half had no behavioral control. In addition, subjects were provided with one of three levels of feedback (success, failure, or no feedback) regarding their performance during the noise. It was expected that information about performance would provide subjects with an increased sense of 'cognitive' control which would affect their appraisal of stressful events and their later performance. The results indicated that subjects given feedback performed better on subsequent tasks than those given no feedback. Perceived behavioral control had little effect on performance. The causal attributions made by subjects were used to interpret these effects. These findings were viewed as supportive of Averill's (1973) notion that various types of control are related to stress in a complex fashion. The data may also support the reformulation by Abramson et al. (1978) of learned helplessness theory.

Foushee, H. C.↗
NASA NTRS1981

Some recent results on extragalactic X-ray sources from the Einstein Observatory

Extragalactic studies by the Harvard/Smithsonian group with the Einstein Observatory have emphasized quasars and galaxy clusters. More than 100 quasars have been detected, including 20 serendipitous discoveries. The X-ray to optical luminosity ratio for radio loud quasars is on the average three times that of radio quiet ones. X-ray images of galaxy clusters reveal a variety of morphological types which may correspond to different stages in their evolution. Several examples of bimodal clusters have been discovered. An X-ray plume associated with M86 appears to be gas being stripped. A mass between 1.7 x 10 to the 13th solar masses and 4.0 x 10 to the 13th solar masses has been derived for M87 from X-ray studies.

Gorenstein, P.↗
NASA NTRS1982

Effects of repetition rate and impulsiveness of simulated helicopter rotor noise on annoyance

Annoyance judgements were obtained for computer generated stimuli simulative of helicopter impulsive rotor noise to investigate effects of repetition rate and impulsiveness. Each of the 82 different stimuli was judged at 3 sound pressure levels by 48 subjects. Impulse repetition rates covered a range from 10 Hz to 115 Hz; crest factors covered a range from 3.2 dB to 19.3 dB. Increases in annoyance with increases in repetition rate were found which were not predicted by common loudness or annoyance metrics and which were independent of noise level. The ability to predict effects of impulsiveness varied between the noise metrics and was found to be dependent on noise level. The ability to predict the effects of impulsiveness was not generally improved by any of several proposed impulsiveness corrections. Instead, the effects of impulsiveness were found to be systematically related to the frequency content of the stimuli. A modified frequency weighting was developed which offers improved annoyance prediction.

Powell, C. A.↗
NASA NTRS1982

Measurement of speech levels in the presence of time varying background noise

Short-term speech level measurements which could be used to note changes in vocal effort in a time varying noise environment were studied. Knowing the changes in speech level would in turn allow prediction of intelligibility in the presence of aircraft flyover noise. Tests indicated that it is possible to use two second samples of speech to estimate long term root mean square speech levels. Other tests were also performed in which people read out loud during aircraft flyover noise. Results of these tests indicate that people do indeed raise their voice during flyovers at a rate of about 3-1/2 dB for each 10 dB increase in background level. This finding is in agreement with other tests of speech levels in the presence of steady state background noise.

Pearsons, K. S.↗
NASA NTRS1982

A new droplet generator

A new droplet generator is described. A loud speaker driven extractor needle was immersed in a pendant drop. Pulsing the speaker extracted the needle forming a fluid ligament which will decay into a droplet. The droplets were sized by stroboscopic photographs. The droplet's size was changed by varying the amplitude of the speaker pulses and the extractor needle diameter. The mechanism of droplet formation is discussed and photographs of ligament decay are presented. The droplet generator worked well on both oil and water based pesticide formulations. Current applications and results are discussed.

Slack, W. E.↗
NASA NTRS1982

A study of resonant-cavity and fiberglass-filled parallel baffles as duct silencers

Acoustical performance and pressure drop were measured for two types of splitters designed to attenuate sound propagating in ducts - resonant-cavity baffles and fiberglass-filled baffles. Arrays of four baffles were evaluated in the 7- by 10-foot wind tunnel number 1 at Ames Research Center at flow speeds from 0 to 41 m/sec. The baffles were 2.1 m high, 305 to 406 mm thick, and 3.1 to 4.4 m long. Emphasis was on measurements of silencer insertion loss as affected by variations of such parameters as baffle length, baffle thickness, perforated skin geometry, cavity size and shape, cavity damping, wind speed, and acoustic field directivity. An analytical method for predicting silencer performance is described and compared with measurements. With the addition of cavity damping in the form of 25-mm foam linings, the insertion loss above 250 Hz of the resonant-cavity baffles was improved 2 to 7 db compared with the undamped baffles; the loss became equal to or greater than the insertion loss of comparable size fiberglass baffles at frequencies above 250 Hz. Variations of cavity size and shape showed that a series of cavities with triangular cross-sections (i.e., variable depth) were superior to cavities with rectangular cross sections (i.e., constant depth). In wind, the undamped, resonant-cavity baffles generated loud cavity-resonance tones; the tones could be eliminated by cavity damping.

Soderman, P. T.↗
NASA NTRS1983

Effects of aircraft noise on human activities

The effects of aircrft noise on human activities was investigated by developing a battery of tasks (1) representative of a range of human activities and (2) sensitive to the disruptive effects of noise. The noise used were recordings of jet aircraft and helicopter sounds at three lvels of loudness--60, 70, and 80 dB(A). Experiment 1 investigated 12 different cognitive tasks, along with two intelligibility tasks included to validate that the noises were being effective. Interference with intelligibility was essentially the same as found in the research literature, but only inconsistent effects were found on either accuracy or latency of performance on the cognitive tasks. When the tasks were grouped into four categories (Intelligibility, Matching, Verbal, and Arithmetic), reliable differences in rated annoyingness of the noises were related to the task category and to the type of noise (jet or helicopter).

Arnoult, M. D.↗
NASA NTRS1983

Human annoyance response to aircraft noise

Human annoyance response to aircraft noise is studied. Subject matter covered includes: emotional response to acoustic noise; loudness differences and scaling techniques.

Galanter, E.↗
NASA NTRS1985

Deriving Strain Modes From Vibrational Tests

Measurements and theoretical analysis complement each other. Experimental acceleration and strain data used to calculate coefficients of low-frequency vibrational modes of object under test. An iterative comparison of experimental and calculated strains give modal model of improved accuracy that predicts strains under operating conditions. Method useful in fatigue life and reliability analyses of buildings, pumps, engines, vehicles, and other systems subject to vibrations and loud noises during operation.

Young, J. W.↗
NASA NTRS1984

The role of knowledge structures in fault diagnosis

The use of human memory and knowledge structures to direct fault diagnosis performance was investigated. The performances of 20 pilots with instrument flight ratings were studied in a fault diagnosis task. The pilots were read a scenario which described flight conditions under which the symptoms which are indicative of a problem were detected. They were asked to think out loud as they requested and interpreted various pieces of information to diagnose the cause of the problem. Only 11 of the 20 pilots successfully diagnosed the problem. Pilot performance on this fault diagnosis task was modeled in the use of domain specific knowledge organized in a frame system. Eighteen frames, with a common structure, were necessary to account for the data from all twenty subjects.

Smith, P. J.↗
NASA NTRS1985

IRAS observations of active galaxies

The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

Neugebauer, G.↗
NASA NTRS1984

On the psychophysics of workload - Why bother with subjective measures?

Psychophysical functions describe the relationship between variations in the amplitude of a defined physical quantity and the psychological perception of these changes. Examples are brightness, loudness, and pain. The regularities of these relationships have been formulated into psychophysical laws. The measurement methodology of psychophysical scaling has been refined by the Harvard group led by Stevens (1957 and 1966), who proposed a power function as a general form for such laws. It is argued here that a similar scaling approach can be adapted to the measurement of workload and task demands based upon subjective estimates. The rationale is that these estimates, like other psychophysical judgments, reflect the individual's perception of the amount of processing resources that the subject invests to meet the demand imposed by a task. This approach was successfully applied to the assessment of 21 experimental conditions given to a group of 60 subjects. The paper discusses the main results of this effort and their implications to theory and application in human performance.

Gopher, D.↗
NASA NTRS1985

A new luminosity component in 3C 48

The infrared emission from the quasar 3C48 has a luminosity L approximately 5 x 10 to the 12th power solar luminosity and dominates the power output of the quasar system. It is shown that the infrared emission, unlike that of most radio loud quasars, is most likely not an extension of the radio emission of the quasar. It is argued that the infrared emission in 3C48 is probably thermal radiation arising in a highly luminous galaxy surrounding the quasar.

Neugebauer, G.↗