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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Crystal-Clear Communication a Sweet-Sounding Success

On July 20, 1969, millions were glued to their television sets when NASA astronaut Neil Armstrong offered these famous words via live broadcast, upon becoming the first man to ever step foot on the Moon. This historic transmission was delivered from Armstrong s headset to the headsets of Mission Control personnel at NASA, and then on to the world. To ensure that this message was delivered loud and clear to all, NASA collaborated with private industry to deliver the best headset-communication technology possible. Today, the heart of this technology beats in a high-end line of lightweight and wireless solutions for homes, offices, contact centers, and dispatch centers.

Source record↗
NASA NTRS2005

Lessons From the Pioneer Venus Program

We began the Pioneer Venus contract in late 1974 with a planned launch of the Orbiter in May 1978 and the Multiprobe in August 1978. Because we had four years, we thought there was plenty of time. As it turned out, we barely made the launch dates. The Orbiter was relatively straightforward, compared to the Multiprobe Bus and Probes that had to survive descent through the harsh Venusian atmosphere. To help overcome our many Multiprobe problems we formed a strong global team. The GE reentry team in Philadelphia, experienced in designing vehicles to enter the earth s atmosphere, was assigned the responsibility for the Probe entry system, including protective heat shielding and parachute design to extract the scienceladen Large Probe pressure vessel and control its descent through the Venusian clouds. Since the Probes had to remain stable as they descended through the Venus atmosphere, we used the aerodynamic expertise at the Hughes Missile Division, NASA s Ames Research Center and the Langley Research Center. Since the pressure at the surface of Venus was equivalent to an ocean depth of 3300 feet, we went to the Navy s David Taylor Research Center for their deepsea expertise. To test the pressure vessel at the high pressure and temperatures anticipated at Venus we went to the only facility capable of simulating the Venus surface environment, the Southwest Research Institute in San Antonio, Texas. We had dozens of subcontractors all over the world. As we developed our design, we began an extensive program to validate the ability of our Probe hardware to withstand the Venus environment. During this testing, we encountered numerous problems, mostly associated with adapting earth-based hardware to operate in the anticipated Venus environment. For example, the Large Probe pressure vessel imploded with a very loud bang the first time we tested its ability to withstand the high pressure and temperature on the Venusian surface. We had to go back and redesign, increasing the pressure vessel wall thickness. In addition, during the first tests of the parachute system, our parachute system ripped apart and had to be redesigned. Finally, at the aptly named test range in Truth or Consequences, New Mexico, we successfully demonstrated the parachute design by drop

Dorfman, Steven D.↗
NASA NTRS2006

Prospects for Pulsar Studies with the GLAST Large Area Telescope

The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST) will have unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 200 GeV. GLAST is therefore expected to provide major advances in the understanding of high-energy emission from rotation-powered pulsars. As the only presently known galactic GeV source class, pulsars will be one of the most important sources for study with GLAST. The main science goals of the LAT for pulsar studies include an increase in the number of detected radio-loud and radio-quiet gamma ray pulsars, including millisecond pulsars, giving much better statistics for elucidating population characteristics, measurement of the high-energy spectrum and the shape of spectral cutoffs and determining pulse profiles for a variety of pulsars of different age. Further, measurement of phase-resolved spectra and energy dependent pulse profiles of the brighter pulsars should allow detailed tests of magnetospheric particle acceleration and radiation mechanisms, by comparing data with theoretical models that have been developed. Additionally, the LAT will have the sensitivity to allow blind pulsation searches of nearly all unidentified EGRET sources, to possibly uncover more radio-quiet Geminga-like pulsars.

Harding, Alice K.↗
NASA NTRS2004

Investigation of Polar Stratospheric Cloud Solid Particle Formation Mechanisms Using ILAS and AVHRR Observations in the Arctic

Satellite observations of denitrification and ice clouds in the Arctic lower stratosphere in February 1997 are used with Lagrangian microphysical box model calculations to evaluate nucleation mechanisms of solid polar stratospheric cloud (PSC) particles. The occurrences of ice clouds are not correlated in time and space with the locations of back trajectories of denitrified air masses, indicating that ice particle surfaces are not always a prerequisite for the formation of solid PSCs that lead to denitrification. In contrast, the model calculations incorporating a pseudoheterogeneous freezing process occurring at the vapor-liquid interface can quantitatively explain most of the observed denitrification when the nucleation activation free energy for nitric acid dihydrate formation is raised by only approx.10% relative to the current published values. Once nucleated, the conversion of nitric acid dihydrate to the stable trihydrate phase brings the computed levels of denitrification closer to the measurements. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and Sb~lctureC: loud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere-composition and chemistry

Irie, H.↗
NASA NTRS2007

Prospects for Pulsar Studies with the GLAST Large Area Telescope

The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST), due to launch in November 2007, will have unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 200 GeV. GLAST is therefore expected to provide major advances in the understanding of high-energy emission from rotation-powered p ulsars. As the only presently known galactic GeV source class, pulsar s will be one of the most important sources for study with GLAST. The main science goals of the LAT for pulsar studies include an increase in the number of detected radio-loud and radio-quiet gamma-ray pulsar s, including millisecond pulsars, giving much better statistics for e lucidating population characteristics, measurement of the high-energy spectrum and the shape of spectral cutoffs and determining pulse profiles for a variety of pulsars of different age. Further, measurement of phase-resolved spectra and energy dependent pulse profiles of the brighter pulsars should allow detailed tests of magnetospheric partic le acceleration and radiation mechanisms, by comparing data with theo retical models that have been developed. Additionally, the LAT will have the sensitivity to allow blind pulsation searches of nearly all un identified EGRET sources, to possibly uncover more radio-quiet Geming a-like pulsars.

Harding, Alice K.↗
NASA NTRS2007

Prospects for Pulsar Studies with the GLAST Large Area Telescope

The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST), due to launch in November 2007, will have unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 200 GeV. GLAST is therefore expected to provide major advances in the understanding of high-energy emission from rotation-powered pulsars. As the only presently known galactic GeV source class; pulsars will be one of the most important sources for study with GLAST. The main science goals of the LAT for pulsar studies include an increase in the number of detected radio-loud and radio-quiet gamma-ray pulsars, including millisecond pulsars, giving much better statistics for elucidating population characteristics, measurement of the high-energy spectrum and the shape of spectral cutoffs and determining pulse profiles for a variety of pulsars of different age. Further, measurement of phase-resolved spectra and energy dependent pulse profiles of the brighter pulsars should allow detailed tests of magnetospheric particle acceleration and radiation mechanisms, by comparing data with theoretical models that have been developed. Additionally, the LAT will have the sensitivity to allow blind pulsation searches of nearly all unidentified EGRET sources, to possibly uncover more radio-quiet Geminga-like pulsars.

Harding, Alice K.↗
NASA NTRS2008

Realism Assessment of Sonic Boom Simulators

Developments in small supersonic aircraft design are predicted to result in low-intensity sonic booms. Booms generated by current aircraft are similar to those that led to the ban on commercial supersonic fli ght over the US, so are unsuitable for parametric studies of psychoac oustic response to low-intensity booms. Therefore, simulators have be en used to study the impact of predicted low-intensity sonic booms. H owever, simulators have been criticized because, when simulating conv entional-level booms, the sounds were observed to be unrealistic by p eople experienced in listening to sonic booms. Thus, two studies were conducted to measure the perceived realism of three sonic boom simul ators. Experienced listeners rated the realism of conventional sonic boom signatures when played in these simulators. The effects on percei ved realism of factors such as duration of post-boom noise, exclusion of very low frequency components, inclusion of ground reflections, a nd type of simulator were examined. Duration of post-boom noise was f ound to have a strong effect on perceived realism, while type of simu lator had a weak effect. It was determined that post-boom noise had t o be at least 1.5 seconds long for the sound to be rated very realist ic. Loudness level did not affect realism for the range of sounds pla yed in the tests (80-93 dB ASEL).

Sullivan, Brenda M.↗
NASA NTRS2007

The Trails of Superluminal Jet Components in 3C 111

The parsec-scale radio jet of the broad-line radio galaxy 3C 111 has been monitored since 1995 as part of the 2cm Survey and MOJAVE monitoring observations conducted with the VLBA. Here, we present results from 18 epochs of VLBA observations of 3C 111 and from 18 years of radio flux density monitoring observations conducted at the University of Michigan. A major radio flux-density outburst of 3C 111 occurred in 1996 and was followed by a particularly bright plasma ejection associated with a superluminal jet component. This major event allows us to study a variety of processes associated with outbursts of radio-loud AGN in much greater detail than possible in other cases: the primary perturbation gives rise to the formation of a forward and a backward-shock, which both evolve in characteristically different ways and allow us to draw conclusions about the workflow of jet-production events; the expansion, acceleration and recollimation of the ejected jet plasma in an environment with steep pressure and density gradients are revealed; trailing components are formed in the wake of the primary perturbation as a result of Kelvin- Helmholtz instabilities from the interaction of the jet with the external medium. The jet-medium interaction is further scrutinized by the linear-polarization signature of jet components traveling along the jet and passing a region of steep pressure/density gradients.

Kadler, M.↗
NASA NTRS2008

Research at NASA on Human Response to Sonic Booms

NASA used its sonic boom simulator to study human response to shaped sonic booms and concluded that a loudness metric, such as Perceived Level, predicts human reaction to outdoor booms more accurately than overpressure. To investigate the importance of indoor phenomena (rattle, reverberation) under controlled laboratory conditions, NASA is building an "indoor sonic boom simulator." The intention is to develop a psychoacoustic model that describes human response as a function of boom shape (spectrum), boom intensity, reverberation, and varying rattle characteristics.

Sullivan, Brenda M.↗
NASA NTRS2007

F15B-Quiet Spike Aeroservoelastic Flight Test Data Analysis

Airframe structural morphing technologies designed to mitigate sonic boom strength are being developed by Gulfstream Aerospace Corporation (GAC). Among these technologies is a concept in which an aircraft's frontend would be extended prior to supersonic acceleration. This morphing would effectively lengthen the vehicle, reducing peak sonic boom amplitude, but is also expected to partition the otherwise strong bow shock into a series of reduced-strength, non-coalescing shocklets. This combination of boom shaping techniques is predicted to transform the classic, high-impulse N-wave pattern typically generated by an aircraft traveling at supersonic speed into a signature more closely resembling a sinusoidal wave with a greatly reduced perceived loudness. 'QuietSpike' is GAC's nomenclature for its recently patented front-end vehicle morphing arrangement. The ability of Quiet Spike to effectively shape a vehicle's far- field sonic boom signature is highly dependent on the area distribution characteristics of the aircraft. The full aeroacoustic benefits of front-end morphing at farfield are only possible when the QuietSpike article and vehicle configuration are designed in consideration of each other. Adding QuietSpike technology to the airframe of an existing, non-boom-optimized supersonic vehicle is unlikely to result in an improved far-field signature due to the generally over-powering influence of wing- and inlet-generated shocks. Therefore, it is generally recognized within NASA and the industry that a clean-sheet vehicle design is required to demonstrate the theoretically predicted far-field aeroacoustic benefits of QuietSpike type morphing and other boom- mitigating concepts. NASA's Aeronautics Research Mission Directorate (ARMD) Supersonics Division has placed increased priority on near-term development and flight-testing of such a vehicle. To help achieve this objective, static and dynamic aerostructural proof-of-concept testing was considered a prudent step prior to a clean-sheet effort in order to reduce risk associated with a follow-on test program. Following a survey of potential test platforms, NASA Dryden's F-15B was selected as the target test vehicle primarily because of its unique ability to carry a largescale test apparatus to relevant supersonic flight speeds, so called the F15 -QS. The QuietSpike test article was constructed primarily of composite materials and attached to the forward fuselage of the F-1 5B bulkhead (see Figures 1,2). The QuietSpike test article replaces the current flight test noseboom and radome assembly. Power is supplied to the Quiet Spike motor assembly in order to extend and retract the Spike, and the Quiet Spike test article was appropriately instrumented with accelerometers, strain gages, pressure transducers, and thermocouples.

Brenner, Martin J.↗
NASA NTRS2009

Measurements of the Flowfield Interaction Between Tandem Cylinders

This paper presents the most recent measurements from an ongoing investigation of the unsteady wake interference between a pair of circular cylinders in tandem. The purpose of this investigation is to help build an in-depth experimental database for this canonical flow configuration that embodies the effects of component interaction in landing gear noise. This new set of measurements augments the previous database at the primary Reynolds number (based on tunnel speed and cylinder diameter) of 1.66 105 in four important respects. First, better circumferential resolution of surface pressure fluctuations is obtained via cylinder "clocking". Second, higher resolution particle image velocimetry measurements of the shear layer separating from the cylinders are achieved. Third, the effects of simultaneous boundary layer trips along both the front and rear cylinders, versus front cylinder alone in the previous measurements, are studied. Lastly, on-surface and off-surface characteristics of unsteady flow near the "critical" cylinder spacing, wherein the flow switches intermittently between two states that are characteristic of lower and higher spacings, are examined. This critical spacing occurs in the middle of a relatively sudden change in the drag of either cylinder and is characterized by a loud intermittent noise and a flow behavior that randomly transitions between shear layer attachment to the rear cylinder and constant shedding and rollup in front of it. Analysis of this bistable flow state reveals much larger spanwise correlation lengths of surface pressure fluctuations than those at larger and smaller values of the cylinder spacing.

Neuhart, Dan H.↗
NASA NTRS2009

Chandra Detection of a Parsec Scale Wind in the Broad Line Radio Galaxy 3C 382

We present unambiguous evidence for a parsec scale wind in the Broad-Line Radio Galaxy (BLRG) 3C 382, the first radio-loud AGN whereby an outflow has been measured with X-ray grating spectroscopy. A 118 ks Chandra grating (HETG) observation of 3C 382 has revealed the presence of several high ionization absorption lines in the soft X-ray band, from Fe, Ne, Mg and Si. The absorption lines are blue-shifted with respect to the systemic velocity of 3C 382 by -840+/-60 km/s and are resolved by Chandra with a velocity width of sigma = 340+/-70 km/s. The outflow appears to originate from a single zone of gas of column density N(sub H) = 1.3 x 10(exp 21)/sq cm and ionization parameter log(E/erg/cm/s) = 2.45. From the above measurements we calculate that the outflow is observed on parsec scales, within the likely range from 10-1000 pc, i.e., consistent with an origin in the Narrow Line Region. Finally we also discuss the possibility of a much faster (0.1c) outflow component, based on a blue-shifted iron K(alpha) emission line in the Suzaku observation of 3C 382, which could have an origin in an accretion disk wind.

Reeves, J. N.↗
NASA NTRS2010

LIGO-VIRGO Triggered Follow-Up with NASA High Energy Photon Survey Missions

We discuss the proposed use of LIGO-VIRGO S6 triggers from comparatively loud events to search for both prompt and afterglow EM counterparts with RXTE, SWIFT and FERMI. Using a 2 or 3-fold coincident trigger from the two LIGO and one VIRGO detectors to provide sky position information, we can search the data from these missions within a limited time window and a constrained portion of their respective FOVs, allowing us to look at a level below the threshold normally used to publicly indicate an event. Since we propose to use these missions in their survey mode, no re-pointing of the missions is envisioned. The search for a coincidence between the data from LIGO-VIRGO and the EM survey missions can then be analyzed off-line; if a coincident EM signal is found it would have a significant effect in establishing the validity of the GW trigger. We discuss some relevant aspects of the NASA missions and give some preliminary estimates of thresholds and coincident background rates.

Camp, Jordan↗
NASA NTRS2010

Evolution of Interplanetary Shocks and their CME Drivers

Shock-driving coronal mass ejections (CMEs) constitute the most energetic phenomena in the heliosphere. The shocks can be identified in a number of ways based on remote-sensing and in situ observations. Type II radio bursts are the earliest indicators of shocks that accelerate electrons to energies up to -10 keV. Solar energetic particle (SEP) events are always accompanied by long wavelength type II bursts indicating that the same shock accelerates ions and electrons. A recent investigation involving a large number of interplanetary (IP) shocks revealed that about 35% of them do not produce type II bursts (radio quiet, RQ) or SEPs. Comparison of the RQ shocks with the radio loud (RL) ones revealed some interesting results such as: (1) the lack of evidence for blast waves,(2) energetic particle enhancement in the shock front in -20% of RQ shocks, and (3) determination of the difference between the RQ and RL shocks in terms of the different kinematic properties of the associated CMEs. On the other hand the shock properties measured at I AU are not too different for the RQ and RL cases. This can be attributed to the interaction with the IP medium, which seems to erase the difference. Implications of this evolution for the geoeffectiveness is also discussed.

Gopalswamy, Natchimuthuk↗
NASA NTRS2010

Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

Bhatia, A. K.↗
NASA NTRS2010

Coronas Mass Ejections, Shocks, and Type II Radio Bursts

Coronal mass ejections (CMEs) are the most energetic phenomena in the interplanetary medium. Type II radio bursts are the earliest indicators of particle acceleration by CME-driven shocks. There is one-to-one correspondence between large solar energetic particle (SEP) events and long wavelength type II bursts because the same CME-driven shock is supposed to accelerate electrons and ions. However, there are some significant deviations: some CMEs lacking type II bursts (radio-quiet or RQ CMEs) are associated with small SEP events while some radioloud (RL) CMEs are not associated with SEP events, suggesting subtle differences in the acceleration of electrons and protons. Not all CME-driven shocks are radio loud: more than one third of the interplanetary shocks during solar cycle 23 were radio quiet. Some RQ shocks were associated with energetic storm particle (ESP) events, which are detected when the shocks arrive at the observing spacecraft. This paper attempts to explain these contradictory results in terms of the properties of CMEs, shocks, and the ambient medium.

Gopalswamy, Natchimuthuk↗
NASA NTRS2010

Influences of the Driver and Ambient Medium Characteristics on the Formation of Shocks in the Solar Atmosphere

Traveling interplanetary (IP) shocks were discovered in the early 1960s, but their solar origin has been controversial. Early research focused on solar flares as the source of the shocks, but when coronal mass ejections (CMEs) were discovered, it became clear that fast CMEs clearly can drive the shocks. Type II radio bursts are excellent signatures of shocks near the Sun. The close correspondence between type II radio bursts and solar energetic particles (SEPs) makes it clear that the same shock accelerates ions and electrons. A recent investigation involving a large number of IP shocks revealed that about 35% of IP shocks do not produce type II bursts or SEPs. Comparing these radio quiet (RQ) shocks with the radio loud (RL) ones revealed some interesting results: (1) there is no evidence for blast waves, in that all IP shocks can be attributed to CMEs, (2) a small fraction (20%) of RQ shocks is associated with ion enhancements at the shocks when they move past the observing spacecraft, (3) the primary difference between the RQ and RL shocks can be traced to the different kinematic properties of the associated CMEs and the variation of the characteristic speeds of the ambient medium, and (4) the shock properties measured at 1 AU are not too different for the RQ and RL cases due to the interaction of the shock driver with the IP medium that seems to erase the difference.

Nat, Gopalswamy↗