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1973-02-01
Technical Paper
730814
A. J. Brammer
The sound pressure levels experienced by an individual exposed to noise can be obtained irrespective of the nature of the source or the presence of acoustic barriers by monitoring the sound field within the ear. The apparatus developed for this purpose consists of a miniature microphone located on the base of the concha connected to a lightweight instrument package strapped to the subject. The latter contains a modified cassette tape recorder, power supplies, and an oscillator used to record a calibration signal onto each tape and check the performance of the system. A pressure transformation is applied during analysis of the data to compensate for the frequency response of the components or to generate an equivalent sound field that would exist at the center of the head in the absence of the subject.
1973-02-01
Technical Paper
730815
M. B. Johnston
A theoretical analysis is presented that predicts significant reductions in exhaust pulse amplitudes and hence exhaust noise levels by varying the shape of the exhaust port in a spark-ignited 2-cycle engine. Verification and correlation with experimental results are also presented.
1973-02-01
Technical Paper
730773
K. F. Nowak
The environmental impact of snowmobile noise has received widespread publicity over the past few years. In order to define and solve any noise problem, a satisfactory and repeatable measurement practice must be evolved. In the case of SAE J192, the particular operating environment of snowmobiles proves a challenge to this task. Environmental conditions affect not only the propagation of sound at the test site, but also the performance of the vehicle itself. This results in a potential for significant variation in the sound pressure level of the sound source. Hence, the test procedure must be designed so as to minimize if not eliminate such sources of variations.
1973-02-01
Technical Paper
730793
J. C. Guignard
The recent work of the International Organization for Standardization (ISO), Technical Committee 108, Mechanical Vibration and Shock, Subcommittee 4 (ISO/TC 108/SC4, Mechanical Vibration and Shock Acceptable to Man) has established guidelines (Draft International Standard ISO/DIS 2631) for the evaluation of human response to whole-body vibration in the range of 1-80 Hz. These guidelines, which are subject to revision and to extension of the frequency range in the light of new and better data, provide a current consensus as to the limits of acceptable human exposure to whole-body vibration in vehicles, buildings, and workplaces, according to selected criteria: comfort, working efficiency, and protection from injury. The limits are expressed in terms of acceleration as a function of direction and frequency of vibration and daily duration of exposure.
1973-02-01
Technical Paper
730792
E. Gunnar Ahlstrom
A farm tractor protection cab made of thin steel sheet pressings is described. The cab is designed and produced using entirely automotive-type procedures. Curved glasses and a dampening suspension of the glasses are found to be an important means of achieving a low noise level in the cab. Using the pressing technique when producing a steel cab makes it possible to give the various cab details rigidity with a minimum of material. When welded together, these details form a very stiff cab body, which gives the necessary mechanical strength. The curved surfaces, the radii, and the round forms, which from a tooling point of view are natural for pressed steel parts, also have a vibration-dampening effect on the entire cab construction, thus making it easier to design a quiet tractor cab. Mounted on a farm tractor of conventional design, the cab meets the noise rating number ISO N85.
1973-02-01
Technical Paper
730748
D. J. Roesler, L. D. Gaddy
This paper describes and summarizes the tests of an electrically propelled tractor-trailer with power on all axles. The test rig showed superior performance over standard tractor-trailer vehicles of the same size and power on highways, beaches, and hills. It demonstrated that electric propulsion for heavy-duty applications can perform well in on-road and off-road applications. Further, it can be made cost effective by utilizing commercially available electrical equipment.
1973-02-01
Technical Paper
730377
R. J. Rulis
The noise goal of 95 PNdB for STOL aircraft imposes severe technology demands on propulsion systems. Effects of this goal on the design of the propulsion system are reviewed. Results from recent development programs associated with STOL noise reduction, such as high bypass fan tests, 25 PNdB acoustic suppression tests, sonic inlets, and powered lift system noise tests, are presented. Integrated propulsion system designs for the blown flap and augmentor wing powered lift systems capable of meeting the noise goal are shown and the performance, installation, and economic penalties assessed.
1973-02-01
Technical Paper
730376
Richard E. Hayden
Proposed powered-lift STOL and RTOL (reduced takeoff and landing) aircraft are expected to require noise reductions on the order of 20 dB to meet community noise goals, according to a number of model and full-scale studies. Propulsive-lift STOL introduces to the designer a new class of noise problems in that the noise sources are exposed and not amenable to conventional muffling. Thus, the noise must be reduced at the source, a task for which thorough understanding of source mechanisms is required. A review of source mechanisms associated with various propulsive lift concepts is presented and current state-of-the-art of prediction technology is assessed for each important source. Sources are rank ordered for the various classes of lift-augmenting concepts. Parametric dependence of source levels on design and operating parameters is discussed. Fundamental concepts for noise reduction are developed and current progress toward implementation of these noise reduction concepts is reviewed.
1973-02-01
Technical Paper
730349
L. T. Goodmanson, B. Williams
This paper discusses the design objectives of and a development cycle for a second-generation supersonic transport (SST). The environmental impact of technological advancement and the rapidly changing economic market produce a wide divergence of possible programs for the 1985 time period. Areas of technological advancement that can move in the direction of the second-generation design objectives will be included. Some of these advances require development of a methodology to be able to reduce the technical risk of application to a commercial SST and some require exploratory development.
1973-02-01
Technical Paper
730656
Lyle V. Rennick
A technique is described for diagnosing the vibration source in a vehicle as it is driven on the road. The basic problem is to determine whether the vibration is related to excessive engine or transmission vibration, driveshaft imbalance, driveline misalignment, U-joints, differential, or whell assembly imbalance; and, in the latter case, to isolate which faulty wheel. The technique developed is to integrate samples of the vibration signal taken synchronously with the various rotating parts. The feasibility of the technique was demonstrated on two heavy trucks and several passenger vehicles.
1973-02-01
Technical Paper
730649
E. Franchini, C. Rossi, P. Filippa
This paper describes the use of a road simulator by Fiat to determine the effects of vibration and loads imposed on various parts of a vehicle. The instrument has been effective in identifying vibration sources that induce fatigue or discomfort or which may cause inefficient operation or a breakdown. The laboratory tests include clear procedures for obtaining preliminary information or for tracing down existing conditions.
1973-02-01
Technical Paper
730500
K. G. Peterson, R. E. Rasmussen
Vehicle/tire system performance is mainly influenced by mechanical properties. This discussion is devoted to radial tires in general, although the data are mostly derived from tests of steel belted radials. Also covered are dimension, handling, ride, traction, noise, and power loss performance of the same tire. The authors conclude that no generic class of tire construction or particular design evaluated thus far is unquestionably superior for every performance parameter, although performance differences between generic classes of tires can be defined statistically.
1973-02-01
Technical Paper
730503
D. E. Malen, E. A. Vaughan
A digital signal analysis system to aid in compiling vibration test data is described. The objectives of the system are explained, mathematical properties are derived, and system operation is discussed with respect to hardware, characteristics, and sample output. This method for digital filtering of time series data has proved to be fast, effective, and an easily implemented method of analyzing structural properties. In addition to providing the design engineer with all of the traditional forms of output offered by analog systems, the computer-based nature of the digital filter system facilitates the use of large-scale dynamic simulations requiring mode identification and other analytical software.
1973-02-01
Technical Paper
730504
Robert J. George
The objective of this paper was to establish the degree of correlation between the results obtained from a 3/8 scale plastic model, an actual frame, and a mathematical computer model. Results showed that a satisfactory dynamic simulation can be obtained from a scaled plastic model of the structure and that a mathematical model composed of beam elements is accurate at the lower frequencies but begins to differ with the actual frame at higher frequencies.
1973-02-01
Technical Paper
730825
M. B. Pearce
Traditional mechanical methods of preventing fasteners from loosening are now being reevaluated. Consumerism has put a priority on safety and reliability which has triggered a move toward a greater use of locking fasteners. The American National Standards Institute Subcommittee B18:20 on the performance of locking fasteners is currently drafting performance specifications on chemical-locking and free-spinning fasteners. The SAE Subcommittee on Vibration Testing of Fasteners has also begun to screen fastener testing equipment. The author of this paper, actively involved with both groups, offers a preview of locking fastener identification, benefits, and problems; also, fastener performance employing the latest transverse shock and vibration equipment, which shows that lock washers do not really lock.
1973-02-01
Technical Paper
730788
Horace F. Howell
This paper outlines the structure and interrelationships of the numerous European standards making organizations, with particular reference to agricultural machinery. Because many of the standards being developed by these organizations are becoming part of legislation in the various Common Market countries, their work is of great interest to the machinery manufacturers. Covered are the highway code-constructional requirements, safety constructional requirements, test codes, and engineering standards. The current status of requirements for lighting, tractor cabs (including structural tests, noise, and emissions), maximum speed limits, brakes, hitches, and safety in the various contries are discussed.
1973-02-01
Technical Paper
730939
Jon C. Calkins, Allan G. Piersol
Laboratory and captive flight experiments were performed using an instrumented Sparrow III missile to evaluate the relative merits of direct mechanical vibration and reverberant acoustic noise tests as techniques for simulating the Sparrow captive flight vibration environment. For the laboratory experiments, the mechanical vibration and acoustic noise excitations were applied in accordance with a common response-controlled test specification. The resulting missile vibration data were then standardized and compared with the vibration levels measured during captive flight to determine their similarity in terms of directional, spatial, and spectral distributions. The results indicate that the acoustic noise test simulated the captive flight vibration more accurately than did the mechanical vibration test. However, the accuracy of the simulation provided by the mechanical vibration excitation was not unacceptable for practical applications.
1973-02-01
Technical Paper
730938
Alan H. Burkhard
Traditional assembled store vibration testing techniques do not realistically simulate a store's captive flight environment. Extensive flight and laboratory testing has shown that an integrated acoustic and vibration shaker technique can realistically reproduce a store's captive flight vibration environment. This paper describes acoustic tests on six flight instrumented stores, giving details of physical setup, test procedure, and test results. Test procedures and analysis of test data are presented for those stores used to evaluate vibration shaker testing techniques.
1973-02-01
Technical Paper
730935
J. B. Bartley, M. J. Turner
The general characteristics of flutter problems affecting the structural design of both subsonic and supersonic transport aircraft are discussed in relation to configuration constraints resulting from mission performance and environmental impact requirements. Combined analytical and experimental approaches employed in the assessment and solution of these problems are outlined. Included are discussions of the extensive application of automated procedures in the use of high-speed digital computers for flutter analysis and the dependence on highly sophisticated wind tunnel flutter model construction techniques to provide reliable experimental data. Illustrations of the application of design techniques to supersonic and subsonic aircraft are presented.
1973-02-01
Technical Paper
730286
Robert L. Paullin
Business aircraft-a nongeneric term to certification authorities-are being given increased attention by national and international bodies concerned with noise reduction. This paper reviews the efforts of these groups from a regulatory standpoint. The status of domestic requirements in the United States and abroad is presented. Technical procedures of promulgated and proposed standards are discussed. Business aircraft are separated into turbojet-powered and propeller-driven categories, and each is presented in terms of recent certification experience. The relationship between domestic certification programs and those of the International Civil Aviation Organization, and between domestic and foreign programs are presented. Finally, a brief look is taken into the future for the efficacy of business aircraft noise certification programs.
1973-02-01
Technical Paper
730288
Frederick B. Metzger, Rose Worobel
Within the next few years tighter restrictions on general aviation aircraft noise are expected. It is anticipated that these noise restrictions, like those imposed on larger transport aircraft now certified under Federal Aircraft Regulations, will be revised downward over a period of time. While it is expected that initial restrictions can be met by the current propeller technology, the larger lower tip speed propellers necessary to meet succeedingly more stringent restrictions may prove difficult to accept. In this paper an alternative to the propeller as a propulsor for general aviation aircraft is discussed. This is the subsonic tip speed low-pressure ratio fan which can be mated to turboshaft, rotary combustion, or reciprocating engines to provide a low noise propulsor in a small package. Information is presented which shows tradeoffs among noise, weight, size, cost, and performance.
1973-02-01
Technical Paper
730289
J. C. Plucinsky
This paper describes the engine design details of the Pratt & Whitney JT15D-1 engine as related to noise generation. Design principles and factors contributing to the very low-noise levels on the Cessna Citation aircraft are illustrated. Noise testing experiences and data from static tests on the United Aircraft of Canada Ltd. (UACL) flight test aircraft and from both static and flight tests on the Citation aircraft are discussed. Lessons learned from these tests and some future probabilities are outlined.
1973-02-01
Technical Paper
730347
Norman Epstein, Bruce J. Gordon
This paper assesses the impact of meeting the environmental requirements for reduced noise and air pollution on the cost and technical design considerations for engines to power the next generation of commercial transport aircraft. Engine candidates studied are in the advanced (new) design class as well as derivatives of existing high-bypass turbofan engines which offer attractive total cost of ownership features. The elements of operating cost are analyzed for the effect of the engine on aircraft economics, with special attention being given to operating cost differences between new engines and those derived from current in-service high-bypass engines.
1973-02-01
Technical Paper
730345
Robert P. Gerend, John P. Roundhill, Albertus D. Welliver
Recent noise technology advancements have provided an increased understanding of true engine noise “floor” levels. This has led to changes in necessary engine cycle requirements for low-noise commercial airplanes. Updated prediction techniques for the core and jet noise sources are described, and lining technology improvements are reviewed. The need for further work in the core noise area is emphasized. The impact of these noise technology revisions on the best engine cycle for obtaining low noise is presented. It is concluded that engines with lower bypass ratios than previously anticipated may be acceptable.
1973-02-01
Technical Paper
730354
John S. Clauss
A successful short-haul transport must satisfy customer and marketplace requirements and be attractive economically. This paper examines the marketplace in the late 1970 time period to determine the payload-range and other performance requirements for a wide-bodied twin-jet transport. Environmental and operating cost targets are established, and the size of the market is estimated. An “optimal” design is then described which essentially represents the best possible airplane using the technology available in the time period best suited to the customer and marketplace requirements. Design data are presented that show the sensitivities of the design to some of the primary configuration variables. Certain design compromises are considered that have to do with airframe commonality with the manufacturer's other transports.
1973-02-01
Technical Paper
730378
H. S. Sweet, H. R. Leslie, J. A. Bennett
A review is presented of low-noise airplanes designed for operation in the 1980 time period. Aircraft with parametric engines covering a range of fan pressure ratios and noise levels were developed conceptually under contract with NASA Advanced Concepts and Missions Division, supported by the NASA Lewis Research Center contracts for the Quiet Clean STOL Experimental Engine (QCSEE) Study Program. Powered-lift concepts included externally blown flap, augmentor wing, internally blown flap, and over-the-wing upper surface blowing. Performance, sizing, and costs are described for 148 passenger airplanes with design field length varying from 2000-4000 ft. Techniques for reducing noise are evaluated in terms of aircraft performance, weight, and cost; experimental data on decayer nozzles are presented and assessed with respect to effectiveness in exhaust noise reduction and aircraft performance penalties.
1973-02-01
Technical Paper
730505
D. L. Flanigan
The essentially modal behavior of an automotive chassis frame in the 0-30 Hz frequency range is confirmed by investigation of a typical frequency response. A mathematical model is developed for which the parameters are to be obtained directly by analysis of vibration test data. The requirements are determined for the instrumentation system and laboratory test setup necessary to obtain accurate estimates of resonant frequencies, mode shapes, and modal mass and damping properties. The determination and importance of the rigid body properties and the “residual compliance” of truncated modes are discussed. Direct comparisons of predicted frequency responses with the original test data demonstrate the validity of the “test-derived model.”
1973-02-01
Technical Paper
730502
T. Sisson, R. Zimmerman, J. Martz
This paper describes methods of determining modal stiffness, inertia, and damping properties of automotive bodies and frames using transient testing techniques. The test equipment described is a digital Fourier analyzer system. The hardware and software used to obtain transfer functions of the vehicle components is discussed, and several examples are presented which compare frequency response data generated by the Fourier analyzer to the same data generated by the more standard sinusoidal excitation methods.
1973-02-01
Technical Paper
730324
G. L. Merrill
This paper reports the results of a study, sponsored by the NASA-Ames Advanced Concepts and Missions Division, of the applicability of small turbofan engines to general-aviation airplanes. Because of its high overall propulsion system efficiency, the turbofan engine is now being chosen for most military and commercial airplanes. To evaluate the turbofan's further applicability to smaller general-aviation airplanes, NASA-Ames and AiResearch have performed a study to establish engine and engine/airplane performance, weight, size, and cost interrelationships, and to evaluate the effects of specific engine noise constraints. The methods whereby these interrelationships and effects were determined, and the results of synthesis and sensitivity analyses are described. In addition to engine cost, engine performance quality was found to be a very important determinant of airplane size and resultant price and operating cost.
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