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Viewing 1 to 30 of 1151
2011-04-12
Journal Article
2011-01-0159
Nicholas R. Oettle, David Sims-Williams, Robert Dominy, Charles Darlington, Claire Freeman
The in-cabin sound pressure level response of a vehicle in yawed wind conditions can differ significantly between the smooth flow conditions of the aeroacoustic wind tunnel and the higher turbulence, transient flow conditions experienced on the road. Previous research has shown that under low turbulence conditions there is close agreement between the variation with yaw of in-cabin sound pressure level on the road and in the wind tunnel. However, under transient conditions, sound pressure levels on the road were found to show a smaller increase due to yaw than predicted by the wind tunnel, specifically near the leeward sideglass region. The research presented here investigates the links between transient flow and aeroacoustics. The effect of small geometry changes upon the aeroacoustic response of the vehicle has been investigated.
2011-05-17
Technical Paper
2011-01-1701
Tongan Wang, John Maxon
Statistical Energy Analysis (SEA) has been used widely by industry and academia for more than 20 years to predict the mid-to-high frequency range behavior of complex acoustic systems. At Gulfstream Aerospace Corporation (GAC), SEA models have been developed to predict the interior cabin noise levels of completed Gulfstream aircraft. These models are also used for acoustic evaluations of design changes prior to implementation as well as a diagnostic tool for investigating noise and vibration issues. Throughout the development of the SEA models, extensive experimental testing in GAC's Acoustic Test Facility (ATF) was conducted on numerous aircraft components represented in the models. This paper demonstrates the importance of using experimental data to improve the accuracy of the SEA predictions by accurately adjusting the material properties and acoustic parameters of the SEA model to better match the ATF experimental data.
2011-05-17
Technical Paper
2011-01-1704
Nickolas Vlahopoulos, Geng Zhang, Ricardo Sbragio
Vehicle design is a complex process requiring interactions and exchange of information among multiple disciplines such as fatigue, strength, noise, safety, etc. Simulation models are employed for assessing and potentially improving a vehicle's performance in individual technical areas. Challenges arise when designing a vehicle for improving mutually competing objectives, satisfying constraints from multiple engineering disciplines, and determining a single set of values for the vehicle's characteristics. It is of interest to engage simulation models from the various engineering disciplines in an organized and coordinated manner for determining a design configuration that provides the best possible performance in all disciplines. The multi-discipline design process becomes streamlined when the simulation methods integrate well with finite element or computer aided design models.
2011-05-17
Technical Paper
2011-01-1733
Kurt Veggeberg, Michael James
Military jet aircraft expose both ground maintenance personnel and the community to high levels of noise. The U.S. Department of Defense is funding research to develop advanced modeling tools for noise reduction techniques and community noise exposure. A large-scale microphone array for portable near-field acoustic holography (NAH) and data acquisition system was created for this purpose. The system was designed for measuring high-amplitude jet noise from current and next-generation military aircraft to provide model refinement and benchmarking, evaluate performance of noise control devices, and predict ground maintenance personnel and community noise exposure. The acoustical instrumentation system was designed to be easy to use with scalable data processing as the primary focus. The data acquisition system allowed up to 152 channels simultaneously sampled at a rate of 96 kHz.
2011-05-17
Technical Paper
2011-01-1667
Sean F. Wu, Na Zhu
A model based approach is developed to track and trace multiple incoherent sound sources in 3D space in real time. This technology is capable of handling continuous, random, transient, impulsive, narrowband and broadband sounds over a wide frequency range (20 to 20,000 Hz). The premise of this technology is that the sound field is generated by point sources located in a free field. To locate these sound sources, iterative triangulations are used based on the signals measured by a microphone array. These signals are preprocessed through de-noising techniques to enhance signal to noise ratios (SNR). Unlike the conventional beamforming, the present technology enables one to pinpoint the exact locations of multiple incoherent sound sources simultaneously by using the Cartesian coordinates, including sources behind measurement microphones. In other words, the microphone array need not face a test object, which is required in the beamforming.
2011-05-17
Technical Paper
2011-01-1647
Kristopher Lynch, John Maxon
Gulfstream Aerospace Corporation (GAC) owns and operates an Acoustic Test Facility (ATF) in Savannah, GA. The ATF consists of a Reverberation Chamber, Hemi-Anechoic Chamber, and a Control Room. Types of testing conducted in the ATF include Transmission Loss, Sound Power, and Vibration testing. In addition to accommodating typical types of acoustic testing, the ATF has some unique capabilities. The ATF can be used to conduct testing at cold temperatures representative of up to 45,000 ft flight altitude, while simultaneously taking Transmission Loss measurements of the chilled test sample. Additionally, the ATF has the capability of conducting Transmission Loss testing of a full mockup of the aircraft sidewall, including a section of fuselage, all the thermal/acoustic materials up to and including the interior decorative panel. A sound source capable of very high amplitudes at high frequencies is required to obtain good measurements from testing multiple wall systems such as this.
2011-05-17
Technical Paper
2011-01-1605
YongHwa Heo, Kwang-joon Kim, Shi-hwan Oh, Dae-kwan Kim, Ki-lyuk Yong, YoungMin Park
Reaction wheels are used to control the attitude of a satellite in space in an almost static manner. Excitation forces at high frequencies as well, however, due to unbalance or bearing faults, can be transmitted to the satellite structure and work badly against missions of the satellite. Hence, counteractions such as vibration isolators are often employed in practice. In this paper, procedures are presented to design and test rubber vibration isolators based on characteristics of the transmission forces without isolators obtained from a previous study. First, a system consisting of reaction wheel, bearing, rigid cover and isolators was modeled with 11 degrees of freedom. Second, stiffness and damping of the isolators were designed such that the forces transmitted onto the satellite structure might satisfy given criteria. Finally, an actual isolation system fabricated using a rubber was tested to check the transmission forces.
2011-05-17
Technical Paper
2011-01-1617
T.S. Miller, S.W. Lee, G. Holup, J.M. Gallman, M.J. Moeller
The turbulent boundary layer (TBL) that forms on the outer skin of the aircraft in flight is a significant source of interior noise. However, the existing quiet test facilities capable of measuring the TBL wall pressure fluctuations tend to be at low Mach numbers. The objective of this study was to develop a new inlet for an existing six inch square (or 6×6) flow duct that would be adequately free from facility noise to study the TBL wall pressure fluctuations at higher, subsonic Mach numbers. First, the existing flow duct setup was used to measure the TBL wall pressure fluctuations. Then the modified inlet was successfully used to make similar measurements up to Mach number of 0.6. These measurements will be used in the future to validate wall pressure spectrum models for interior noise analysis programs such as statistical energy analysis (SEA) and dynamic energy analysis (DEA).
2010-10-17
Technical Paper
2010-36-0550
Aleksandras Jagniatinskas, Oleksandr Zaporozhets, Oleg Kartyshev, Boris Fiks
For assessment of the aircrafts noise impact on the community near to airports the acoustic calculations and measurements may be used. Obtained measurements results show ~1 dBA for LAeq coincidence with calculations results and allow to prepare correct database for practical use under ECAC method. While results of LAmax estimation still remain under investigation. These requirements are important first of all for aircraft, which are designed in FSU, Russian Federation and Ukraine. Their contribution to the aircraft noise impact in airports of FSU countries is still dominant, so their correct input data is still necessary.
2010-10-17
Technical Paper
2010-36-0538
Mario Triches Jr., Micael G. V. do Carmo, Vinicius L. Gouveia
Without available direct measurements, the only method of assessing the impact of a completely new aircraft or power-plant design is to utilize a reliable prediction procedure. Such a procedure may be able to make use if a limited amount of directly relevant data, for instance, engine test data, or may have to rely entirely upon empirical component prediction procedures. Traditional aircraft noise prediction procedures based on engine static noise data are generally costly in time, since the engine source separation process is not a straightforward task, demanding several side routines to make it feasible. This paper attempts to present a new and simplified approach to assess community noise levels of a new aircraft design based on static engine noise data. The simplified procedure proposes an alternative to the complete engine source separation process, based on the definition of master parameters like jet noise cut-off frequencies, tonal frequencies and resultant broadband spectra.
2010-10-17
Technical Paper
2010-36-0546
Giuliano Quiqueto, Luiz Chamon, Sylvio Bistafa
In order to generate in-flight acoustic and vibration fields inside an aircraft cabin mock-up, an N&V simulator was developed. The preliminary work on the development, setup and characterization of the N&V simulator will be presented. Firstly, an overview of the system will be given, including the desired input signals, followed by the presentation of the control software, which was developed to simplify the operation of the system by end users during routine testing. Secondly, the set-up strategy to adjust the reproduction of levels and spectrum of both acoustic and vibration fields will be presented, along with comparative vibroacoustics results between the mock-up and original in-flight recordings. Finally, a discussion on different methods for adjusting the simulator reproduction by means of optimal filtering is made, and further developments are presented.
2010-10-17
Technical Paper
2010-36-0545
Fred Mendonca, Alex Read, Fabiano Imada, Vinicius Girardi
The transport industries face a continuing demand from customers and regulators to improve the acoustic performance of their products: reduce noise heard by passengers and passersby; avoid exciting structural modes. In both the aerospace and automotive areas, flow-induced noise makes a significant contribution, leading to the desire to understand and optimize it through the use of simulation. Historically, the need for time-consuming, computationally expensive transient simulations has limited the application of CFD in the field of acoustics. In this paper are described efficient simulation processes that, in some instances, remove the requirement for transient analyses, or significantly reduce the total process time through intelligent pre-processing. We will outline this process and provide both automotive and aerospace industrial examples, including analyses of highly complex geometries found in real life.
2010-10-17
Technical Paper
2010-36-0519
Jean-Pierre Coyette, Julien Manera
Abstract Numerical simulation techniques are widely used in automotive and aircraft sectors. The optimization of industrial products with respect to acoustic performance requires appropriate modeling strategies in order to handle various noise sources and different propagation paths. The present paper focuses on the application of finite element techniques (FE) to the solution of vibro-acoustic and aero-acoustic problems. State-of-the-art FE techniques are reviewed and illustrated by appropriate examples.
2010-10-17
Technical Paper
2010-36-0522
Dominique Collin
The X-NOISE Coordination Action, through its network structure and comprehensive workplan involving expert groups, scientific workshops, stakeholder seminars and a common information system, addresses the aircraft noise challenges set by the ACARE 2020 Vision. To this end, X-Noise undertakes the elaboration and coordination of research strategies, the dissemination of results and the integration of European research activities in the field of air transport related to noise. Over 4 years, the project has involved strong participation from European Union-based organizations as well as significant contribution from international partners, combining the complementary skills and expertise of industry, SMEs, universities and research establishments to cover the whole field of interest.
2010-10-17
Technical Paper
2010-36-0520
Delia Dimitriu, Dragos Munteanu, Octavian Pleter
This paper is assessing two methods that can be used in assessing the airport noise capacity when new operational practices are implemented at a certain airport. The example given is CDA-continuous descent approach implemented at Bucharest Henri Coanda International airport in Romania. A review of the main operational practices related to CDO (Continuous Descent Operations) with relevance for noise and emissions reduction, shows the importance of working in a team when implementing new operational practices, as well as the need to access data either through FDR (flight data recorder) or from measurements. - The example selected explains the difficulties one can have to extract FDR data. Although the authors of this paper benefitted from FDR from TAROM, the Romanian national airline, it was difficult to be extracted, so the assessment of the airport noise capacity focused on monitoring and measurements undertaken under the flight path.
2010-10-17
Technical Paper
2010-36-0526
Jerome E. Manning, Chadwyck T. Musser, Alice Botteon Rodrigues
Statistical Energy Analysis (SEA) is an established high-frequency analysis technique for generating acoustic and vibration response predictions in the automotive, aerospace, machinery, and ship industries. SEA offers unique NVH prediction and target-setting capabilities as a design tool at early stages of vehicle design where geometry is still undefined and evolving and no prototype hardware is available yet for testing. The exact frequencies at which SEA can be used effectively vary according to the size and the amount of damping in the vehicle subsystems; however, for automotive design the ability to predict acoustic and vibration responses due to both airborne and structure-borne sources has been established to frequencies of 500 Hz and above. This paper presents the background, historical use, and current industrial applications of structure-borne SEA. The history and motivation for the development of structure-borne SEA are discussed.
2010-10-17
Technical Paper
2010-36-0506
Micael G. V. do Carmo, Julio R. Meneghini
The Brazilian Silent Aircraft Program (Programa "Aeronave Silenciosa) is an initiative of six Brazilian Universities and Institutes (USP-Poli "University of Sao Paulo - Polytechnic School, USP/EESC - University of Sao Paulo - Sao Carlos Engineering School, UFSC - Federal University of Santa Catarina, UFU - Federal University of Uberlandia, UnB - University of Brasilia and IAE - Brazilian Institute of Aeronautics and Space) together with Embraer to develop methodologies and solutions for the aircraft external noise problem. The main goal of this initiative is to study and develop methodologies that will allow estimation of aircraft noise generation and propagation through three main approaches: numerical simulation (CAA), analytical and semi-empirical models, and wind tunnel and flight tests.
2010-10-17
Technical Paper
2010-36-0514
Pieter Sijtsma
An introduction is given of phased array beamforming techniques for locating acoustic sources. Starting from basic principles, the Conventional Beamforming technique is described. It is explained how this technique can be applied to wind tunnel measurements. Further, a number of advanced array processing techniques are discussed. One chapter is devoted to the array processing technique for the location of moving sources. This technique can be applied to rotating sources, for example on wind turbine blades, and to source location on aircraft flying over a microphone array.
2011-09-11
Technical Paper
2011-24-0218
Mikael Karlsson, Mats Abom, Ragnar Glav
The inclusion of flow-acoustic interaction effects in linear acoustic multiport models has been studied. It is shown, using a T-junction as illustration example, that as long the acoustic system is linear the required information is included in a scattering matrix obtained by experimental or numerical studies. Assuming small Mach numbers and low frequencies-as in most automotive silencer applications-the scattering matrix for the T-junction can be approximated using quasi-steady models. Models are derived that holds for all possible configurations of grazing and bias flow in the T-junctions. The derived models are then used to predict the performance of a novel silencer concept, where a resonator is formed by acoustically short-circuiting the inlet and outlet ducts of a flow reversal chamber. The agreement between experiments and simulations is excellent, justifying the use of the quasi-steady modeling approach.
2004-11-02
Technical Paper
2004-01-3129
Zenovy S. Wowczuk, Kenneth H. Means, Victor H. Mucino, Gregory J. Thompson, Lawrence Feragotti, James E. Smith, Adam Naternicola, Bruce J. Corso
Abstract During structural engineering design two of the most overlooked design facets of a finished product is understanding the behavior characteristics of how the product will react when resonated at its natural frequencies and actually defining and understanding the overall vibration profile responsible for the excitation of the structure. A C-130 mechanical arm/pod system has been developed to accommodate 1,000-pounds of sensor payload deployable in flight from a C-130 Hercules military aircraft (variants B thru J). The mechanical arm/pod system will be subjected to a profile of vibration from numerous sources during deployment and while in the final operating position. A general vibration profile for the mechanical arm/pod will be compiled from the plane’s four T-56-A-15 turboprop engines, the atmospheric turbulence and random gust loads.
2010-06-09
Journal Article
2010-01-1423
Jens Weber, Ismail Benhayoun
To achieve “right first time” design for SAAB projects, thus avoiding unnecessary development loops, a squeak & rattle simulation tool was required. This paper presents a new squeak & rattle simulation approach which covers the complete development process of interior parts. The process starts with a rough model, which is mainly based on styling data and ends with a model of a very high detail level close to serial tooling status. The detailed CAD model is then represented by a simulation model of similarly increasing quality. By using different types of analyses in the frequency and time domains (modal analysis, frequency response and transient analysis), the output of these simulations can be matched to the available FE model quality. During initial development the global behavior of the structure is of interest. Finally the relative displacement between two detailed trim parts is used to evaluate the risk for squeak & rattle.
2012-11-25
Technical Paper
2012-36-0620
Alejandro Osses, Ismael Gomez, Max Glisser, Christian Gerard, Ricardo Guzman
In this paper an algorithm for the classification of aircrafts composing the commercial fleet currently operating in the Chilean airspace is described. This classification is based on certain acoustic descriptors obtained at a specific noise monitoring point, which are used as inputs for a Feed-Forward Artificial Neural Network. As a result, determined classification groups for the evaluated aircraft models are obtained, so that aircrafts of similar size and technology belong to the same group.
2012-10-02
Technical Paper
2012-36-0526
Gregorio G. Azevedo, Marcelo Bustamante, Julio A. Cordioli, Samir N. Y. Greges, Jeff Weisbeck, Andre de Oliveira
The Hybrid FE-SEA method is a recently developed numerical technique that deals with the so-called mid-frequency problem. Such problems involve the dynamic analysis of systems that include, at the same frequency range, components with high and low modal density. Systems with a reduced number of modes are usually modeled using deterministic methods, as the Finite Element (FE) Method, while modal dense systems need to be treated by means of statistical methods such as the Statistical Energy Analysis (SEA). Neither FE nor SEA can properly describe a system that displays the mid-frequency behavior due to a prohibitive computational cost (FE) or the lack of accuracy (SEA). The floor structure of an aircraft is a typical case of a mid frequency problem, where the floor beams are relatively rigid and have very few modes while the floor panels have a very high modal density.
2013-05-13
Journal Article
2013-01-1929
Ganapathi Balasubramanian, L.A.Raghu Mutnuri, Zen Sugiyama, Sivapalan Senthooran, David Freed
A computational process for early stage vehicle shape assessment for automotive front window buffeting and greenhouse wind noise is presented. It is a challenging problem in an experimental process as the vehicle geometry is not always finalized. For example, the buffeting behavior typically worsens during the vehicle development process as the vehicle gets tighter, leading to expensive late counter measures. We present a solution using previously validated CFD/CAA software based on the Lattice Boltzmann Method (LBM). A CAD model with realistic automotive geometry was chosen to simultaneously study the potential of different side mirror geometries to influence the front window buffeting and greenhouse wind noise phenomena. A glass mounted mirror and a door mounted mirror were used for this comparative study. Interior noise is investigated for the two phenomena studied. The unsteady flow is visualized and changes in the buffeting and wind noise behavior are explored.
2013-05-13
Journal Article
2013-01-1930
Patricia Manning, Jerome Manning, Chadwyck Musser, George Peng
The contribution of wind noise through the glasses into the vehicle cabin is a large source of customer concern. The wind noise sources generated by turbulent flow incident on the vehicle surfaces and the transmission mechanisms by which the noise is transmitted to the interior of the vehicle are complex and difficult to predict using conventional analysis techniques including Computational Fluid Dynamics (CFD) and acoustic analyses are complicated by the large differences between turbulent pressures and acoustic pressures. Testing in dedicated acoustic wind tunnel (AWT) facilities is often performed to evaluate the contribution of wind noise to the vehicle interior noise in the absence of any other noise sources. However, this testing is time-consuming and expensive and test hardware for the vehicle being developed is often not yet available at early stages of vehicle design.
2013-05-13
Journal Article
2013-01-1932
Robert Powell, Philippe Moron, Ganapathy Balasubramanian, Barbara Neuhierl, Sivapalan Senthooran, Bernd Crouse, David Freed, Cornelia Kain, Frank Ullrich
Wind noise is a significant source of interior noise in automobiles at cruising conditions, potentially creating dissatisfaction with vehicle quality. While wind noise contributions at higher frequencies usually originate with transmission through greenhouse panels and sealing, the contribution coming from the underbody area often dominates the interior noise spectrum at lower frequencies. Continued pressure to reduce fuel consumption in new designs is causing more emphasis on aerodynamic performance, to reduce drag by careful management of underbody airflow at cruise. Simulation of this airflow by Computational Fluid Dynamics (CFD) tools allows early optimization of underbody shapes before expensive hardware prototypes are feasible. By combining unsteady CFD-predicted loads on the underbody panels with a structural acoustic model of the vehicle, underbody wind noise transmission could be considered in the early design phases.
2013-05-13
Journal Article
2013-01-1933
Sivapalan Senthooran, L.A.Raghu Mutnuri, Joe Amodeo, Robert Powell, Claire Freeman
For most car manufacturers, wind noise from the greenhouse region has become the dominant high frequency noise contributor at highway speeds. Addressing this wind noise issue using experimental procedures involves high cost prototypes, expensive wind tunnel sessions, and potentially late design changes. To reduce the associated costs as well as development times, there is strong motivation for the use of a reliable numerical prediction capability early in the vehicle design process. Previously, a computational approach that couples an unsteady computational fluid dynamics solver (based on a Lattice Boltzmann method) to a Statistical Energy Analysis (SEA) solver had been validated for predicting the noise contribution from the side mirrors. This paper presents the use of this computational approach to predict the vehicle interior noise from the windshield wipers, so that different wiper placement options can be evaluated early in the design process before the surface is frozen.
2014-05-05
Journal Article
2014-01-9099
Lindsay J. Miller, Susan Sawyer-Beaulieu, Edwin Tam
Polyurethane (PU) foam is used for many automotive applications with the benefits of being lightweight, durable, and resistant to heat and noise. Applications of PU foams are increasing to include non-traditional purposes targeting consumer comfort. An example of this is the use of PU foam between the engine and engine cover of a vehicle for the purpose of noise abatement. This addition will provide a quieter ride for the consumer, however will have associated environmental impacts. The additional weight will cause an increase in fuel consumption and related emissions. More significant impacts may be realized at the end-of-life stage. Recycling PU foams presents several challenges; a lack of market for the recyclate, contamination of the foams, and lack of accessibility for removal of the material.
2014-11-04
Technical Paper
2014-36-0785
Augusto Amador Medeiros, Zargos Neves Masson, Pablo Giordani, Julio Cordioli
Abstract With the increase in aircraft transportation and, consequently, aircraft noise in the last decades, measurement of acoustic liner impedance under grazing flow has become a point of interest. Different indirect methodologies have been developed by independent research groups to solve this problem. The Mode-Matching technique and, more recently, the Two-Port method are examples of developed methodologies that use acoustic pressure measurements in a test rig where a liner sample is subject to grazing mean flow to educe its impedance. In this paper, both methods are explained, implemented and used to educe the acoustic impedance of different liner samples in a recently developed grazing flow impedance eduction test rig. Additionally, both methods are compared based on their computational cost and limitations.
2013-04-08
Technical Paper
2013-01-1001
Koji Norisada, Masaharu Sakai, Syunsuke Ishiguro, Masami Kawaguchi, Franck Perot, Koichi Wada
In recent years, vehicle cabin quietness takes a growing importance particularly related to the emergence of hybrid and electric vehicles and “Idle Stop system” vehicles. Demand for quieter car air-conditioner systems is increasingly important also, especially the reduction of the flow-induced noise from the HVAC. In HVAC systems, the rotating blower is one of the main noise sources and the digital solution for predicting and analyzing the blower aeroacoustic noise in the early stage of design is needed for developing a quieter blower. The target of this study is to develop and to validate a flow-induced noise predictive tool for a HVAC blower and to analyze the noise source. In this paper, a low-dissipation, transient, compressible CFD/CAA approach based on the Lattice Boltzmann Method (LBM) is used to predict simultaneously the flow and aeroacoustic radiation of two production blowers.
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