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The Global ETD Search service is a free service for researchers
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Showing 11 to 20 of 20 (0.044 seconds)Spelling suggestions: "subject:"airplanes.these"" "subject:"airplanes.we""
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Effects of jet aircraft overflights and other potential disturbances on behavioral responses and productivity of nesting peregrine falconsNordmeyer, Dana L. 08 April 1999 (has links)
In order to examine the potential impact of military jet overflights and other disturbances on productivity of peregrine falcons (Falco peregrinus), we observed behavioral reactions of peregrines to disturbances at nests along the Tanana River, Alaska during the 1995-1997 breeding seasons. Military jets conducted low-altitude flights over a sample of nests under observation in each year (experimental nests), while other nests were not intentionally overflown (reference nests). Other disturbances occurred at random. Animal noise monitors (ANMs), which collect and store data on noise disturbance levels, were deployed at each observed nest. A total of 878 above-threshold (��� 85 dB) overflights were recorded by the ANMs during the course of the study. A total of 401 close (defined as ��� 1000 m slant distance from the nest) overflights by subsonic F-16, F-15, A-10, Harrier, Jaguar, or Tornado jet aircraft were recorded during observations. Close overflights by military jets accounted for 63% of all observed potential disturbances at experimental nests; they accounted for 2.6% of all observed potential disturbances at reference nests. Other potential disturbances at reference nests included civilian fixed-wing aircraft (41%), boats (33%), avian predators (17%),
helicopters (5%), and mammalian predators (1%). Peregrine falcons responded
differently to animate and inanimate sources of disturbance, and responded most intensely
and most frequently to other raptors, particularly conspecifics. Flight reactions were common, but not in response to inanimate sources. Among inanimate potential disturbances, falcons responded most intensely to boats (6% of reactions involved flight), and least intensely to helicopters (3%) and fixed-wing aircraft (2%). Intensity of reactions to military jets was indistinguishable from that to either boats or other aircraft. Intense behavioral responses (including flight reactions) to military jet overflights were rarely observed in this study, even at slant distances <500 m, and no intense behavioral responses were observed at slant distances >550 m. Peregrine falcon productivity (number of fledglings produced per nesting attempt) in the study area was within the normal range for Interior Alaska and the Tanana River. Dose of jet aircraft disturbance was not correlated with productivity. Productivity was, however, negatively correlated with reactivity of both individual falcons and mated pairs. Those falcons that responded more intensely to overflights tended to have lower productivity. The sensitivity of
breeding peregrine falcons to low-altitude jet overflights is a better indicator of subsequent productivity than actual dose of overflights. This is likely a reflection of lower parental quality/investment among breeding pairs with high reactivity (i.e., younger, less experienced parents are less likely to be productive). / Graduation date: 1999
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Aircraft noise stress and the effects on human health : a cross-sectional study in metropolitan MinnesotaMeister, Edward A. 29 April 1996 (has links)
Although the adverse auditory effects of noise have been the focus of
occupational health research for decades, little is known about the nonauditory health
effects that result from noise exposure. The focus of this research was the
nonauditory health effects of exposure to commercial aircraft noise (CAN)
overflights. It was theorized that CAN exposure resulted in an ongoing stress-response
that had the potential to be harmful to human health over time. Two
aspects of CAN were considered; the sound level intensity (dBA), and the frequency
of overflights.
Data were collected by a stratified random sampling design in the CAN
exposed neighborhoods of Eagan, St. Paul, Minneapolis, and Bloomington, and in
control communities of Shoreview and Mounds View, all located in Minnesota
(n=4000). A written questionnaire was used to measure; (1) health (MOS-36 Scale),
(2) behavioral and emotional coping strategies, (3) noise sensitivity, (4) annoyance
levels, and (5) demographic data. Aircraft noise levels and overflight data were
obtained in cooperation with the Metropolitan Airport Sound Abatement
Commission.
Results showed significantly higher stress levels and lower health measures by
CAN exposure type. These findings occurred primarily in communities exposed to
high frequencies of aircraft overflights. Multivariate analysis revealed significant
reductions for the three main health measures of General Health (GH), Sense of
Vitality (Vitality), and Mental Health (MH), based on CAN exposure type. Post-hoc
contrast analysis indicated that GH, Vitality, and MH scores were worst with high
frequency of overflights.
Behavioral copers had significantly fewer stress symptoms and used fewer
stress medications than non-behavioral copers. Non-normalized emotional copers
had significant negative associations with Gil, Vitality, and MH; however, these
correlations were weak. Noise sensitivity levels were not significantly different
among the CAN exposed communities; however noise annoyance levels were
significantly higher than controls, and were the highest with high frequency of
overflights.
Finally, multivariate analysis of covariance indicated significant reduction for
health measures based on CAN exposure types after adjusting for all effect modifiers
(covariates) in the study. Vitality was the most consistently impacted by CAN
exposure, and this was particularly the case for subjects exposed to high frequency of
aircraft overflights. / Graduation date: 1996
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Jet noise of high aspect-ratio rectangular nozzles with application to pneumatic high-lift devicesMunro, Scott Edward 12 1900 (has links)
No description available.
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The automatic identification of aerospace acoustic sourcesCabell, Randolph H. 21 November 2012 (has links)
This work describes the design of an intelligent recognition system used to distinguish noise signatures of five different acoustic sources. The system uses pattern recognition techniques to identify the information obtained from a single microphone. A training phase is used in which the system learns to distinguish the sources and automatically selects features for optimal performance. Results were obtained by training the system to distinguish jet planes, propeller planes, a helicopter, train, and wind turbine from one another, then presenting similar sources to the system and recording the number of errors. These results indicate the system can successfully identify the trained sources based on acoustic information. Classification errors highlight the impact of the training sources on the system's ability to recognize different sources. / Master of Science
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A study of active control techniques for noise reduction in an aircraft fuselage modelJones, James D. January 1987 (has links)
A simplified cylindrical model is used to investigate the elementary mechanisms of control of sound transmission into aircraft cabins by two active control techniques: propeller synchrophasing and active vibration control. Propeller synchrophasing involves controlling the relative rotational phase of the engines to achieve maximum cabin noise reduction. Active vibration control involves structurally controlling the vibrational response of the cabin wall to reduce the important modes which transmit their energy into the cabin.
Noise reductions for harmonic excitation at acoustic cavity resonance are shown to be in excess of 20 dB throughout most of the cavity whether synchrophasing or active vibration control is used. Off-resonance reductions are substantially less due to increased modal density requiring a larger number of actuators for effective control of the complex sound field. Additional studies were performed using synchrophasing in conjunction with active vibration control to study their joint capabilities in controlling complex sound fields. The dual control system displayed improved control performance with noise reductions on the order of 25-35 dB and a more uniform sound field. Also, the complementary control characteristics of the system clearly demonstrated effective control of orthogonal acoustic modes of the cavity. However, the improved effectiveness of the control system was dependent upon judiciously positioning the actuators for optimal control of the sound field.
An independent study was performed to identify the effects of a complex geometry on sound transmission into an aircraft fuselage model interior. For this study, a geometrically scaled cabin floor was installed in the unstiffened test cylinder to investigate the structural and acoustic influence of the simulated cabin floor. Results indicated that the stiffening of the cylindrical model associated with insertion of the floor strongly influenced the structural response of the cylinder but generally had little effect on the coupled pressure response. Conversely, the modification of the interior acoustic cavity tended to have little influence on the cylinder response but substantially reduced the coupled pressure response.
Thus, this investigation identified the fundamental mechanisms of control of sound transmission into simplified models of aircraft fuselages by active control techniques. / Ph. D.
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The effects of low-level flying military aircraft on the reproductive output of osprey in Labrador and northeastern Québec /Thomas, Peter W., 1969- January 1999 (has links)
The objective of this study was to determine whether low-level flying military aircraft affected the reproductive success of Osprey (Pandion haliaetus), and if so, to determine the optimal avoidance distance to minimize these effects. I studied 49 nests in 1995, and 68 nests in 1996 within the military low-level flying zone. Nest occupancy, clutch size, number of hatchlings, and number of young at 41 days of age were assessed at each nest. GIS flight track records provided frequency of aircraft at given distances and altitudes from the nest. Logistic regression analysis assessed the impact of flight frequency in four distance categories and four altitude categories on Osprey reproduction. The frequency of flights within each category were not accurate predictors of Osprey reproductive output. Nests were then randomly assigned to a buffer-zone radius of either 0, 1.85, 3.7, or to a control of 7.4 km, and reproductive output was compared among treatments, and between years. No significant differences were discovered among the reproductive parameters within either 1995 or 1996, but reproductive output was significantly higher in 1995, likely due to adverse weather conditions experienced in 1996.
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The effects of low-level flying military aircraft on the reproductive output of osprey in Labrador and northeastern Québec /Thomas, Peter W., 1969- January 1999 (has links)
No description available.
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Modeling the transmission loss of typical home constructions exposed to aircraft noiseFiresheets, Nathan 14 November 2012 (has links)
Current aircraft noise guidelines are based primarily on outdoor sound levels. However, human perception is highly related to indoor response, particularly for residences. A research project has been conducted that provides insight into how typical residential dwelling envelopes affect sound transmitted indoors. A focus has been placed on the effect of residential dwelling envelopes on subsonic civil aircraft noise. Typical construction types across the United States have been identified and used to develop model predictions of outdoor-to-indoor transmission loss. While it was initially hypothesized that these construction types could be grouped by climate region, it was found that these constructions are better grouped according to their outermost construction layer. Further, the impact of systematically altering construction variables (such as the construction materials used and the ratio of window area to wall area) has been investigated. Results will be used to better understand trends for expected noise reduction for typical construction types around the United States. Additionally, comparisons have been made between the effect of older and more modern wall construction techniques on whole-house performance.
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Influence of vane sweep on rotor-stator interaction noise.Envia, Edmane. January 1988 (has links)
In this dissertation the influence of vane sweep on rotor-stator interaction noise is investigated. In an analytical approach, the interaction of a convected gust, representing the rotor viscous wake, with a cascade of finite span swept airfoils, representing the stator, is analyzed. The analysis is based on the solution of the exact linearized equations of motion. High-frequency convected gusts for which noise generation is concentrated near the leading edge of the airfoils are considered. In a preliminary study, the problem of an isolated finite span swept airfoil interacting with a convected gust is analyzed. Using Fourier transform methods and the Wiener-Hopf technique, an approximate solution for this problem is developed. Closed form expressions for the acoustic farfield are obtained and used in a parametric study to assess the effect of airfoil sweep on noise generation. Results indicate that sweep can substantially reduce the farfield noise levels for a single airfoil. Utilizing the single airfoil model, an approximate solution to the problem of noise radiation from a cascade of finite span swept airfoils interacting with a convected gust is derived. Only upstream radiated noise is considered. Neglecting the weak coupling between the adjacent leading edges at high frequencies, the cascade solution is constructed as a superposition of acoustic farfields emanating from an infinite number of isolated airfoils. A parametric study of noise generated by gust-cascade interaction is then carried out to assess the effectiveness of vane sweep in reducing rotor-stator interaction noise. The results of the parametric study show that, over a fairly wide range of conditions, sweep is beneficial in reducing noise levels. One conclusion of particular importance is that rotor wake twist or circumferential lean substantially influences the effectiveness of vane sweep. The orientation of the vane sweep must be chosen to enhance the natural phase lag caused by wake lean, in which case rather small sweep angles substantially reduce the noise levels.
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Evaluation of the Hybrid-Electric Aircraft Project Airbus E-Fan XBenegas Jayme, Diego January 2019 (has links) (PDF)
Purpose - This master thesis evaluates the hybrid-electric aircraft project E-Fan X with respect to its economical and environmental performance in comparison to its reference aircraft, the BAe 146-100. The E-Fan X is replacing one of the four jet engines of the reference aircraft by an electric motor and a fan. A turboshaft engine in the cargo compartment drives a generator to power the electric motor. --- Methodology - The evaluation of this project is based on standard aircraft design equations. Economics are based on Direct Operating Costs (DOC), which are calculated with the method of the Association of European Airlines (AEA) from 1989, inflated to 2019 values. Environmental impact is assessed based on local air quality (NOx, Ozone and Particulate Matter), climate impact (CO2, NOx, Aircraft-Induced Cloudiness known as AIC) and noise pollution estimated with fundamental acoustic equations. --- Findings - The battery on board the E-Fan X it is not necessary. In order to improve the proposed design, the battery was eliminated. Nevertheless, due to additional parts required in the new configuration, the aircraft is 902 kg heavier. The turboshaft engine saves only 59 kg of fuel. The additional mass has to be compensated by a payload reduced by 9 passengers. The DOC per seat-mile are up by more than 10% and equivalent CO2 per seat-mile are more than 16% up in the new aircraft. --- Research limitations - Results are limited in accuracy by the underlying standard aircraft design calculations. The results are also limited in accuracy by the lack of knowledge of some data of the project. --- Practical implications - The report contributes arguments to the discussion about electric flight. --- Social implications - Results show that unconditional praise given to the environmental characteristics of this industry project are not justified.
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