Showing papers on "Aircraft noise published in 2002"

A Prospective Study of Some Effects of Aircraft Noise on Cognitive Performance in Schoolchildren

Abstract: Before the opening of the new Munich International Airport and the termination of the old airport, children near both sites were recruited into aircraft-noise groups (aircraft noise at present or pending) and control groups with no aircraft noise (closely matched for socioeconomic status). A total of 326 children (mean age = 10.4 years) took part in three data-collection waves, one before and two after the switch-over of the airports. After the switch, long-term memory and reading were impaired in the noise group at the new airport. and improved in the formerly noise-exposed group at the old airport. Short-term memory also improved in the latter group after the old airport was closed. At the new airport, speech perception was impaired in the newly noise-exposed group. Mediational analyses suggest that poorer reading was not mediated by speech perception, and that impaired recall was in part mediated by reading.

Multilevel modelling of aircraft noise on performance tests in schools around Heathrow Airport London

Abstract: Study objective: To examine the effects of chronic exposure to aircraft noise on children’s school performance taking into account social class and school characteristics. Design: This is a cross sectional study using the National Standardised Scores (SATs) in mathematics, science, and English (11 000 scores from children aged 11 years). The analyses used multilevel modelling to determine the effects of chronic aircraft noise exposure on childrens’ school performance adjusting for demographic, socioeconomic and school factors in 123 primary schools around Heathrow Airport. Schools were assigned aircraft noise exposure level from the 1994 Civil Aviation Authority aircraft noise contour maps. Setting: Primary schools. Participants: The sample were approximately 11 000 children in year 6 (approximately 11 years old) from 123 schools in the three boroughs surrounding Heathrow Airport. Main results: Chronic exposure to aircraft noise was significantly related to poorer reading and mathematics performance. After adjustment for the average socioeconomic status of the school intake (measured by percentage of pupils eligible for free school meals) these associations were no longer statistically significant. Conclusions: Chronic exposure to aircraft noise is associated with school performance in reading and mathematics in a dose-response function but this association is confounded by socioeconomic factors.

Research into Landing Gear Airframe Noise Reduction

Abstract: Servere air-traffic constraints are imposed by commercial airports following public complaints about the ever increasing noise impact. This situation lead to renewed emphasis by aviation industry into aircraft noise source research. While the engine noise still dominates during aircraft full-power take-off, it is the airframe noise which represents the essential contributor to the overall flyover noise signature in the landing phase for today's high-bypass ratio engine powered large commercial aircraft. Therefore in Europe a research project was launched aiming at the reduction of landing gear noise, which is the dominant airframe noise component for wide-body aircraft and the subject area of this paper. Based on the knowledge of a state-of-the-art full scale A340 nose- and main-landing gear baseline noise test, realistic noise reduction add-on devices were developed for these gears and the devices' effectiveness tested in a dedicated wind tunnel study. Both farfield noise data were taken and techniques employed for noise source localization. By removing the noise reduction devices orderly, their individual effectiveness were assessed. It was demonstrated that significant noise reduction can be achieved with add-on devices which have been designed to cause minimum interference with respect to the gears' functionality and maintainability.

Social survey of community response to a step change in aircraft noise exposure.

Abstract: Community response to a step change in aircraft noise exposure associated with the opening of a new runway at Vancouver International Airport was documented in two rounds of telephone interviews. One round of interviews was conducted 15 months prior to the start of operations on the new runway, while a second round of interviews was undertaken 21 months after the start of operations. The proportion of respondents who described themselves as “very” or “extremely” annoyed by aircraft noise in a residential area with increased aircraft noise exposure after the runway opening was markedly greater than that predictable from well-known dosage–response relationships. Analysis suggests that a good part of the “excess” annoyance is attributable to the net influence of nonacoustic factors.

Validation of a Semiempirical Airframe Noise Prediction Method through Dedicated A319 Flyover Noise Measurements

Abstract: To counter balance the detrimental effect on aircraft noise around airports due to the continuous increase in air-traffic, measures for aircraft source noise reduction must be taken. In contrast to a full power take-off, where such efforts must be directed towards a reduction of engine noise levels, for the final approach phase airframe noise sources are the dominating contributors to the overall noise signature and thus need to be tackled. Within a joint effort between DLR and Deutsche Lufthansa AG flyover noise tests were conducted on an Airbus A319 aircraft to determine its airframe noise radiation characteristics and to validate airframe source noise prediction models as derived from wind tunnel experiments. Flight tests were performed with the high lift devices in their baseline configuration and with some modifications at the slat-tracks and flap side-edges to avoid excessive flow noise generation at structural details of real aircraft components. For this "low noise" aircraft configuration flyover airframe noise data compare well with airframe noise data as acquired within different wind tunnel studies both on a complete A320 scale model aircraft and on a full-scale A320 wing section.

A Tool for Low Noise Procedures Design and Community Noise Impact Assessment: The Rotorcraft Noise Model (RNM)

Abstract: To improve aircraft noise impact modeling capabilities and to provide a tool to aid in the development of low noise terminal area operations for rotorcraft and tiltrotors, the Rotorcraft Noise Model (RNM) was developed by the NASA Langley Research Center and Wyle Laboratories. RNM is a simulation program that predicts how sound will propagate through the atmosphere and accumulate at receiver locations located on flat ground or varying terrain, for single and multiple vehicle flight operations. At the core of RNM are the vehicle noise sources, input as sound hemispheres. As the vehicle "flies" along its prescribed flight trajectory, the source sound propagation is simulated and accumulated at the receiver locations (single points of interest or multiple grid points) in a systematic time-based manner. These sound signals at the receiver locations may then be analyzed to obtain single event footprints, integrated noise contours, time histories, or numerous other features. RNM may also be used to generate spectral time history data over a ground mesh for the creation of single event sound animation videos. Acoustic properties of the noise source(s) are defined in terms of sound hemispheres that may be obtained from theoretical predictions, wind tunnel experimental results, flight test measurements, or a combination of the three. The sound hemispheres may contain broadband data (source levels as a function of one-third octave band) and pure-tone data (in the form of specific frequency sound pressure levels and phase). A PC executable version of RNM is publicly available and has been adopted by a number of organizations for Environmental Impact Assessment studies of rotorcraft noise. This paper provides a review of the required input data, the theoretical framework of RNM's propagation model and the output results. Code validation results are provided from a NATO helicopter noise flight test as well as a tiltrotor flight test program that used the RNM as a tool to aid in the development of low noise approach profiles.

Experimental evaluation of leaky least-mean-square algorithms for active noise reduction in communication headsets

Abstract: An adaptive leaky normalized least-mean-square (NLMS) algorithm has been developed to optimize stability and performance of active noise cancellation systems. The research addresses LMS filter performance issues related to insufficient excitation, nonstationary noise fields, and time-varying signal-to-noise ratio. The adaptive leaky NLMS algorithm is based on a Lyapunov tuning approach in which three candidate algorithms, each of which is a function of the instantaneous measured reference input, measurement noise variance, and filter length, are shown to provide varying degrees of tradeoff between stability and noise reduction performance. Each algorithm is evaluated experimentally for reduction of low frequency noise in communication headsets, and stability and noise reduction performance are compared with that of traditional NLMS and fixed-leakage NLMS algorithms. Acoustic measurements are made in a specially designed acoustic test cell which is based on the original work of Ryan et al. ["Enclosure for low frequency assessment of active noise reducing circumaural headsets and hearing protection," Can. Acoust. 21, 19-20 (1993)] and which provides a highly controlled and uniform acoustic environment. The stability and performance of the active noise reduction system, including a prototype communication headset, are investigated for a variety of noise sources ranging from stationary tonal noise to highly nonstationary measured F-16 aircraft noise over a 20 dB dynamic range. Results demonstrate significant improvements in stability of Lyapunov-tuned LMS algorithms over traditional leaky or nonleaky normalized algorithms, while providing noise reduction performance equivalent to that of the NLMS algorithm for idealized noise fields.

Relationship between low-frequency aircraft noise and annoyance due to rattle and vibration.

Abstract: A near-replication of a study of the annoyance of rattle and vibration attributable to aircraft noise [Fidell et al., J. Acoust. Soc. Am. 106, 1408–1415 (1999)] was conducted in the vicinity of Minneapolis-St. Paul International Airport (MSP). The findings of the current study were similar to those reported earlier with respect to the types of objects cited as sources of rattle in homes, frequencies of notice of rattle, and the prevalence of annoyance due to aircraft noise-induced rattle. A reliably lower prevalence rate of annoyance (but not of complaints) with rattle and vibration was noted among respondents living in homes that had been treated to achieve a 5-dB improvement in A-weighted noise reduction than among respondents living in untreated homes. This difference is not due to any substantive increase in low-frequency noise reduction of acoustically treated homes, but may be associated with installation of nonrattling windows. Common interpretations of the prevalence of a consequential degree of annoyance attributable to low-frequency aircraft noise may be developed from the combined results of the present and prior studies.

The Need for a Specific Noise Measurement for Population Exposed to Aircraft Noise during Night-time.

Abstract: Most of subjective complaints about aircraft noise during night-time refers to sleep disruption. In order to protect populations who live around airports, it is of major importance to define levels of noise considered to be unacceptable during that particular time of the 24-hour period. In addition to an integrated indicator which describes the global noise exposure (Lden), the French authority on airport noise control (Autorite de Controle des Nuisances Sonores Aeroportuaires: ACNUSA) is considering the possibility of defining a maximum noise level [LAmax (1s)] that should not be exceeded at night (from 22.00 to 06.00) by any flying aircraft over residential areas. The main benefit of this single event indicator would be the identification of contravening vessels and application of possible penalty. It is believed that this type of sanction would help protecting sleep in highly noise-exposed areas.

Night-time Noise Annoyance: State of the Art.

Abstract: The annoyance-reaction is one of the central variables in noise research After an introduction to different concepts and definitions of noise annoyance different scales of how noise annoyance can be measured are shown The question is discussed whether disturbance effects of noise at different times of day are given To clarify this problem, the results of a series of actual German noise studies are reported In these studies differences between day- and night­time annoyance are found depending on the sound sources For the case of road traffic noise no differences between day and night-time annoyance were found In contrast, annoyance reactions are related to the time of day for railway and air traffic noise Especially for aircraft noise, above a Leq of 50 dB(A) night-time annoyance rises faster than day-time annoyance The effects are discussed in the frame of a cognitive model of noise annoyance It is argued that annoyance judgments are based on an internal representation of the noise situation Part of this representation are the event characteristics of the sound sources and their estimated impacts for disturbances at different times of day

Integrated noise model

Abstract: The main objective of this workshop presentation is to provide information about the efforts, policy studies, and products of the Noise Division in the Federal Aviation Administration's Office of Environment and Energy (AEE-100). AEE-100 develops aviation noise standards, provides measurements, and predicts aviation noise by developing tools for quantifying the predicted impact. In addition, AEE-100 evaluates new aircraft engines and operating procedures and formulates research and development objectives to reduce aviation noise.

Evaluation of an Aircraft Concept With Over-Wing, Hydrogen-Fueled Engines for Reduced Noise and Emissions

Abstract: This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A strut-braced wing configuration with overwing, ultra-high bypass ratio, hydrogen fueled turbofan engines is considered. Estimated noise and emission characteristics are compared to a conventional configuration designed for the same mission and significant benefits are identified. The design challenges and technology issues which would have to be addressed to make the concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program seeks to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify enabling advanced technology requirements for the concepts.

Aircraft noise exposure from schiphol airport: a relation with complainants.

Abstract: The possible relation between aircraft noise exposure and the prevalence of complainants around Schiphol airport was studied. The home address of people who complain about aircraft noise at the Environment Advisory Committee Schiphol was combined with annual average noise levels, using a Geographic Information System. The prevalence of complainants in areas with different noise exposure was calculated. In addition, data from a questionnaire survey was used to gain insight into the influence of sound insulation, personal characteristics, and aspects of health on complaint behaviour. The prevalence of complainants increases from < 1% at 50 dB(A) (Lden) to about 7% at 62 dB(A). Above this level the prevalence drops back to < 3%. An increase in the percentage of sound insulated houses with increasing noise levels is observed, rising markedly above 60 dB(A) (from 24% to almost 90%). When comparing people who complain with those who do not complain about aircraft noise, complainants report more noise annoyance (OR=10.2, 95% CI=8.54-12.3), sleep disturbance (OR=9.87, 95% CI=8.19-11.9), concern about health (OR=8.02, 95% CI=6.75-9.53), and fear for an aircraft crash (OR=3.64, 95% CI=3.07-4.31). Results indicate a relation between aircraft noise exposure and the prevalence of complainants, possibly influenced by sound insulation. Important determinants of complaint behaviour apart from noise level are noise annoyance, sleep disturbance, concern about health, and fear for an aircraft crash. Although complainants do not seem to be representative for the total population, and do not reflect the full extent of noise annoyance, their prevalence does reflect the regional distribution of aircraft noise annoyance in a noise polluted area.

The social side of noise annoyance

Abstract: Unfairness increases noise annoyance Noise annoyance increases due to unfair sound management. Fair sound management reduces annoyance, however only when the sound pressure level is high, concludes Eveline Maris based on two laboratory experiments. Being exposed to man-made sound is more than mere exposure: it is a social experience, too: You expose Me. This social hypothesis of noise annoyance has been confirmed in two laboratory experiments. Participants were exposed to aircraft noise (sound pressure level (SPL): 50 or 70 dB A) and treated either in a neutral, fair, or unfair manner. The results show that besides SPL, also the fairness of the procedure determines the level of noise annoyance. The first experiment shows an interaction effect of procedural fairness and SPL: annoyance ratings are significantly lower in the fair than in the neutral condition, but the effect is found only when SPL is 70 dB. The second experiment shows a main effect of procedural unfairness on noise annoyance: annoyance ratings are significantly higher in the unfair than in the neutral conditions, regardless of SPL. The findings imply that, in addition to noise reduction engineering, application of knowledge on the social side of noise annoyance can help reduce future noise annoyance levels.

Development of an advanced continuous descent concept based on a 737 simulator

Abstract: It is well known that noise restrictions impact airport approach and departure procedures at many airports worldwide The research described here presents an advanced continuous descent approach (CDA) concept using current and future capabilities of flight management systems (FMS) to allow idle thrust (low noise) descent from about 8000 ft to 2000 ft, yielding significant reductions in aircraft noise on the local airport community The advances in flight management technology described here would allow tailoring of the final descent path to include aircraft type, predicted winds, initial altitude, vehicle weight, time of arrival, and initial/final descent speeds This research is based on a high fidelity simulation of a 737-700 aircraft Conclusions and techniques based on this aircraft would have to be adjusted or re-tuned before they are applied to other aircraft types to correctly match thrust/drag characteristics

The Effect of the Urban Street Canyon on the Noise from Low Flying Aircraft

Abstract: The effect of urban streets on the noise from a low-flying aircraft has been investigated. The study first involved the development of a prediction method based on geometrical acoustics with the assumption of specular reflections. The effect of a variety of street configurations on the transmission gain was investigated and analysed in terms of changes in street geometry. The relative Effective Perceived Noise Level was also predicted. The predictions show that for specular reflections the relative Effective Perceived Noise Level increases in proportion to the ratio of building height to flying altitude, however, changing the street width has only a minor effect. The effect of mixed specular and diffuse reflections was investigated using a commercial acoustical modelling package and it was shown that although the effect on the transmission gain was small, the scattering of sound energy out of the street channel resulted in a decrease in the value of the relative Effective Perceived Noise Level with the ra...

Lateral attenuation of aircraft sound levels over an acoustically hard water surface : Logan Airport study

Abstract: During the summer of 1999, in order to examine the applicability of currently available mathematical models of lateral sound attenuation, a noise measurement study was conducted at Logan International Airport in Boston, Massachusetts. It was revealed through analysis of the data collected that lateral attenuation is a function of the location of the engines on the aircraft, i.e., tail-mounted versus wing-mounted. In addition to that included in existing aircraft noise models, attenuation for aircraft with tail-mounted engines was found to agree with the published literature. For wing-mounted engines, attenuation was found to be less than that documented in the literature. A general under-prediction of side-line noise by the existing noise models is the result of this lower lateral attenuation for aircraft with wing-mounted engines.

Assessment Of Noise Impacts At Airports

Abstract: Airport operation is a major source of community concerns due to aircraft noise emissions particularly in locations close to airports and aircraft flight tracks. The effects of aircraft noise on humans can cause hearing damage for people working at airports and speech and sleep interference which can develop into stress for nearby communities. As such, it becomes essential when locating and designing to expand airports to optimize flight paths in a way to reduce noise exposure to nearby communities. For this purpose, it is required to assess changes in noise levels resulting from new runway configurations, evaluate increased aircraft operation demand, new fleet mix, revised routings and airspace structures, alternative flight profiles, and modifications to other operational procedures. This paper presents a noise impact assessment for the proposed expansion at the Beirut International Airport, Lebanon. Field noise measurements were collected at sensitive noise receptors along selected locations around the airport and the corresponding airport traffic flow was characterized. A mathematical model was then applied to simulate noise levels as a function of the different airplane classes, operations, flight path, and landing characteristics. The model was also used to predict future noise levels, optimize airplane flight path, and assess mitigation measures to minimize potential aircraft noise impacts.

Corrective measures for the aircraft noise models NORTIM and GMTIM: 1. Development of new algorithms for ground attenuation and engine installation effects. 2. New noise data for two aircraft families.

Abstract: The routines for ground effect and engine installation effect developed in this project improve calculation accuracy for the aircraft noise models NORTIM and GMTIM. For a sample of nearly 70.000 measurements at Gardermoen, the overall improvement is in the order of 1 dB for equivalent noise levels (SEL). Noise data extracted from the measurement program at Gardermoen in 2001 further improves the accuracy by 0.5 dB for SEL. It is recommended that updated versions of the two programs should be used in noise calculations as an interim solution until a revised recommendation (either from ECAC or SAE) for lateral attenuation appears. An international co-operative work is needed to supply noise data from normal operations for all aircraft in the database. It is recommended that new noise data be implemented as they occur.

Large Scale Frequency Domain Numerical Simulation of Aircraft Engine Tone Noise Radiation and Scattering

Abstract: The engines represent a major source of aircraft noise both at take off and landing. For the large turbofan engines used nowadays on commercial aircraft, fan noise dominates in particular during approach flight and landing, when the thrust force necessary from the jet is relatively small. The tonal noise generated by fan rotor-stator interaction as cylindrical duct modes is radiated from the fan inlet and exhaust and is scattered by the various surfaces surrounding the nacelle, such as fuselage and wing. Eventually both the direct and the scattered field propagate to the far field through the complex mean flow around the aircraft. Earlier studies of fan inlet noise propagation either incorporate only the effects of the nacelle boundary layer [4] or consider the flow around the nacelle axisymmetric and inviscid [10, 8]. However, the non-uniform flow around the nacelle and the relative positions of the nacelle, fuselage and wing offer the designer a range of options for reducing the noise footprint of an aircraft. A numerical simulation of the phenomenon, which is a very convenient alternative to experiments at least in the initial design stage, represents a large-scale computational problem which becomes feasible using the recent developments in computational methods for advanced architecture computers. Time-domain methods have been proposed by various authors, including the present ones [9, 12, 14], to address this problem. Under that approach, it is straightforward to have a full nonlinear model for the sound propagation, based on the inviscid flow (Euler) equations, that applies both for take-off and landing. The use of an explicit low-storage time integration method avoids the need to store and solve a matrix at each time step, thus keeping the computer memory requirements relatively low. In this paper we present a different and complementary methodology based on the frequency domain solution of the linearized full potential equation. The possibility to solve for the acoustic field in one step as a boundary value problem must in this case be weighed against the difficulty of finding the solution of a system of equations with complex coefficients. As the size of this system increases rapidly with the frequency, a direct solution even using sparse solvers is precluded by the large memory requirements. An efficient method for its iterative solution must be devised. The paper first introduces the governing equations for the sound propagation problem. A new treatment of the radiation boundary conditions in the form of an augmented, perfectly matched layer (PML) equation, is then presented. This new equation allows us to have

Flight experiments for aircraft noise measurement using "tunnel-in-the-sky" display

Abstract: A series of flight experiments to measure aircraft noise were conducted using the National Aerospace Laboratory of Japan’s MuPAL-e research helicopter and MuPAL-α research airplane. In addition to longitudinal flight profiles such as level, climbing and descending flight, steady turns were flown to measure noise in the plane of the main rotor tip-path of the helicopter and in the wing tip direction of the airplane. The use of “Tunnel-In-the-Sky” (TIS) displays presented on the programmable cockpit display systems enabled precise tracking of the desired flight paths. Flight data such as aircraft position, attitude, and air data obtained from on-board data acquisition systems were used to determine accurately the direction of noise propagation. This paper presents the obtained noise directivity patterns, as well as the flight profiles and their errors to demonstrate the effectiveness of applying TIS display technology to noise measurement flight experiments.

Noise Abatement and Control: An Overview of Federal Standards and Regulations

Abstract: Constant or repeated exposure to sounds of 90 decibels or higher can lead to hearing loss, and noise exposure is responsible for hearing impairment in about 10 million people in the United States. To limit the public’s exposure to potentially harmful sound levels, the federal government sets and enforces uniform noise standards for aircraft and airports, interstate motor carriers and railroads, workplace activities, medium and heavy-duty trucks, motorcycles and mopeds, portable air compressors, federal highway projects, and federal housing projects. State and local governments determine the extent to which other sources are regulated, including commercial, industrial, and residential activities. Numerous bills were introduced in the 107 Congress to address noise exposure. Aside from appropriations for airport noise mitigation grants in FY2002, none of them were enacted. The majority of this legislation focused on aircraft noise, including: H.R. 299, H.R. 1288, H.R. 1741, H.R. 2299, H.R. 2429, H.R. 2430, H.R. 2477, H.R. 2746, H.R. 3479, H.R. 3886, H.R. 4481, H.R. 4653, H.R. 5142, H.R. 5143, H.R. 5559, S. 633, S. 688, S. 1786, S. 2039, S. 2808, and S. 2966. Other bills addressed noise in national parks and on public lands: S. 365, S. 712, S. 1136, and S. 1151. Two bills addressed railway noise: H.R. 2811 and H.R. 4761. Other legislation, H.R. 1130, would have authorized grants to examine the effects of noise and other environmental aspects on student achievement in elementary and secondary schools. Another bill, H.R. 1116 would have reauthorized EPA’s former Office of Noise Abatement and Control. Due to ongoing concerns about noise exposure in many affected communities, a similar body of legislation may be considered during the 108 Congress. This report will be updated as relevant developments occur.

Revolutionary Concepts for Helicopter Noise Reduction: SILENT Program

Abstract: As part of a NASA initiative to reduce helicopter main rotor noise, a Phase 1 study has been performed of candidate noise reduction concepts. Both conventional and novel design technologies have been analyzed that reduce the community impact of helicopter operations. In this study the noise reduction potential and design implications are assessed for conventional means of noise reduction, e.g., tip speed reduction, tip shapes and airfoil tailoring, and for two innovative design concepts: modulated blade spacing and x-force control. Main rotor designs that incorporate modulated blade spacing are shown to have reduced peak noise levels in most flight operations. X-force control alters the helicopter's force balance whereby the miss distance between main rotor blades and shed vortices can be controlled. This control provides a high potential to mitigate BVI noise radiation. Each concept is evaluated using best practice design and analysis methods, achieving the study's aim to significantly reduce noise with minimal performance degradation and no vibration increase. It is concluded that a SILENT main rotor design, incorporating the modulated blade spacing concept, offers significantly reduced noise levels and the potential of a breakthrough in how a helicopter's sound is perceived and judged. The SILENT rotor represents a definite advancement in the state-of-the-art and is selected as the design concept for demonstration in Phase 2. A Phase 2 Implementation Plan is developed for whirl cage and wind tunnel evaluations of a scaled model SILENT rotor.

Recent advances in active noise and vibration control at NASA Langley Research Center

Abstract: Over the past 15 years NASA has investigated the use of active control technology for aircraft interior noise. More recently this work has been supported through the Advanced Subsonic Technology Noise Reduction Program (1994–2001), High Speed Research Program (1994–1999), and through the Quiet Aircraft Technology Program (2000–present). The interior environment is recognized as an important element in flight safety, crew communications and fatigue, as well as passenger comfort. This presentation will overview research in active noise and vibration control relating to interior noise being investigated by NASA. The research to be presented includes: active control of aircraft fuselage sidewall transmission due to turbulent boundary layer or jet noise excitation, active control of interior tones due to propeller excitation of aircraft structures, and adaptive stiffening of structures for noise, vibration, and fatigue control. Work on actuator technology ranging from piezoelectrics, shape memory actuators, and fluidic actuators will be described including applications. Control system technology will be included that is experimentally based, real‐time, and adaptive.

Reducing aircraft noise with computer graphics

Abstract: Excessive noise is a part of almost everyone's life, whether it comes from the next-door neighbor running his leaf blower or cars driving by with stereos blasting. But for those who live near airports or air force bases, noise is a constant distraction that can cause stress and other health-related problems. For the military and commercial airlines, more stringent noise emission standards are increasingly becoming an issue, as they must try to meet federal guidelines or face restrictive night-flight rules, increased no-fly zones, and additional airport fees. For these reasons, industries, governments, and educational institutions such as Pennsylvania State University are conducting research to help reduce the noise pollution caused by jets and helicopters. Penn State's aerospace engineering department has been using high-end parallel computers, virtual reality systems, and advanced visualization software to test the causes of aircraft noise and find ways to reduce it.

Aircraft noise propagation - the simplest case

Abstract: Geometrical spreading, air absorption, and refraction are the main wave phenomena that govern the propagation of aircraft noise. The results of this study make possible the calculate noise at ground level in terms of the sound exposure level, LAE. The model applies to an aircraft with a nondirectional radiation pattern (e.g., helicopter, one-engine propeller) while the atmosphere is at rest. The derived equations provide some insight into the nature of noise propagation, that can be useful for teaching purposes.

Airport Noise and Environmental Justice in South Africa

Abstract: Aircraft noise around airports has been a controversial issue for the past four decades. Successive international meetings have resulted in the adoption of noise limit rules and this has resulted in generally decreasing airport noise in developed countries. However, the louder aircraft appear to have been sold on to airlines in the developing world. This paper traces the agreements and their consequences for those living near airports in South Africa.

Military aircraft noise and nonlinear acoustics

Abstract: A new joint program between Wyle Laboratories, Penn State, and others has been initiated to develop a better noise model for military fighter aircraft. As is well known, the high sound amplitudes produced by modern jets imply the importance of nonlinear effects in the sound propagation. In the literature one can find several experiments clearly showing spectral broadening and the development and coalescence of shocks as the noise propagates with distance. Current U.S. DoD noise models, nevertheless, neglect nonlinear distortion. A number of different nonlinear propagation predictions schemes are available, and currently there is no broad consensus as to which models work best for jet noise. This talk will discuss the applicability of several of these methods to the current need. Only when nonlinear propagation methods have been coded and tested against laboratory and full scale measurements will a predictive tool be available for assessing the environmental noise impacts of modern aircraft. [Work supporte...