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There are many different vibration sources in a car. Engine, gears, road roughness, impacts against the wheels cause vibration and sound that can decrease the parts and the car durability as well as affect drivability, safety and passengers and community comfort. In 4×4 cars, some extra vibration sources are the parts responsible for transmitting the torque and power to the rear wheels. Each of them has their own vibration modes, excited mostly by its imbalance or by the second order engine vibration. The engine vibration is a very well known phenomena and the rear driveshaft is designed not to have any vibration mode in the range of frequencies that the engine works or its second order. The imbalance of a driveshaft is also a design requirement. That means, the acceptable imbalance of the driveshaft is limited to a maximum value.

The “Rigidization-on-Command”™ (ROC™) resin development has focused on the development of resin systems that use UV light cure for rigidization. Polymeric sensitizers have been incorporated into the resin formulations to promote cure using Pen-Ray lamps and UV light-emitting diodes (LED's). Formulations containing the polymeric sensitizers were examined by FTIR and DSC. Complete cure was observed after 15 min. exposure with the Pen-Ray lamps. Performance of the Pen-Ray lamps and UV LEDs was thoroughly characterized. Thermal models were developed to optimize the performance of the of the MLI insulation thermal oven used for orbital cure of the boom. Results show that -12°C is the lowest temperature required for cure of the ROC™ resin systems.

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.

Presented in this paper is a brief review of momentum exchange theory for Jet Noise Suppression. “Experimental Results from Scale Model Tests” are included. These data exhibit peak to peak attenuation of 20 db along maximum exhaust noise azimuths at a nozzle pressure ratio of 3.1.

Engineers doing squeak and rattle testing of instrument panels (IP's) have successfully used large electrodynamic vibration systems to identify sources of squeaks and rattles (S&R's). Their successes led to demands to test more IP's, i.e., to increase throughput of IP's to reflect the many design, material, and/or manufacturing process changes that occur, and to do so at any stage of the development, production, or QA process. What is needed is a radically different and portable way to find S&R's in a fraction of the time and at lower capital cost without compromising S&R detection results.

Over the last ten years there has been a steady growth in the market share of light-duty diesel engines, especially in Europe. At the same time, a general trend in petrol engine development has been seen, in which normal aspirated engines are being replaced by downsized turbocharged engines. Therefore, NVH engineers have to deal with new challenges. Turbochargers produce an aerodynamic noise in the frequency range above 1000Hz, which might influence the exterior and interior noise level. As a result, the additional requirement for acoustical components to reduce this flow noise is going to pose an increasing challenge for air intake system suppliers. This paper describes a new design of well-known wide band silencer first mentioned by A. Selamet, N.S.Dickey and J.M.Novak [1,2]. The silencer works according to the interference principle. The sound is guided into two or more parallel pipes of different lengths.

The extensive use of rotative machines in the diverse branches of the modern world has made the rising undesirable mechanical and acoustic vibration levels to be a problem of special importance for the machines normal operation as for the communities that are each time more affected by the problem. It makes the study of vibration and acoustic phenomena also to be even more important and the applications of its concepts more sophisticated. Several are the concepts used for decreasing vibration levels, like common dampers, hydraulic dampers, active dampers, natural frequencies changes and others. The choice of use of one or another depends greatly on the engineering possibilities (weight, energy, physical space, other components functional interference, vibration levels, etc.) as well as the cost of implementation of each one.

This paper presents a new design method for solving the vehicle vibration problem induced by engine drive, by using a μ-synthesis. We have tried the active control of engine mounts to insulate the vibration of engine. We experimented on the effects by using computer simulation and vibration simulator. Computer simulation results show that resonance peak can be effectively reduced. We have also confirmed the effect of vibration simulator, which shall be reported in this paper.

SIMULTANEOUS RECORDINGS of cylinder pressure, audible sound, and crankshaft motion have shown that rumble is a noise associated with bending vibrations of the crankshaft. The vibrations are caused by abnormally high rates of pressure rise near the top dead center piston position. In this study the high rates of pressure rise were obtained by inducting deposits into the the engine. Thud is a torsional vibration of the crankshaft, similar in sound to rumble but resulting from much earlier occurrence of the maximum rates of pressure rise. Rumble vibrations consisted of a fundamental frequency of 600 cps and higher harmonics in the 11/1 compression ratio V-8 laboratory engine used in the investigation. The audible noise of rumble was predominantly composed of the second harmonic or about 1200 cps.

THE FIRST YEAR of jet airline operation has brought many problems — and satisfactions — to the industry. Here the author discusses some of the more serious problems: 1. Scheduling. American Airlines used the “Monte Carlo” method to calculate payloads and flight times. 2. Baggage handling. Almost nothing annoys a passenger more than long waits for baggage at the end of a flight. One approach to the problem is the baggage expediter system. 3. Mechanical shutdowns. 4. Runway length. 5. Noise. Noise suppressors have not been effective enough, from the standpoint of communities surroundings airports. Development of the turbofan engine offers some hope in this area.*

THE effects on the transmission of vibration through isolation mounts of machine and foundation resilience, and of wave propagation are investigated. The prediction of the effectiveness of mounts is discussed, and curves are presented for estimating their effectiveness under certain conditions. A number of conclusions are drawn relevant to the problems of mount design and selection.

THE usefulness of planetary gear trains and the engineering techniques necessary for optimum design are discussed in this paper. A simple method for calculating planetary gear ratios is described which can be used to determine quickly the potential usefulness of any planetary configurations. The author lists criteria which help to evaluate the potential of a planetary gear train schematic from the standpoints of gear noise and structural viewpoint. Detailed design of individual members include spacing of the pinions, mounting considerations, thrust direction, lubrication, and stress evaluation.

THIS PAPER outlines progress to October, 1958, on the new Shock and Vibration Manual. At that point, the methods of solving vibration isolation problems had been established. After further refinements and expansion, the manual will be issued by SAE Committee S-12 on Shock and Vibration. The manual will set up procedures to be followed by engineers who don't have extensive experience in the field. It will give procedures for problems having up to six degrees of freedom. The procedure, as described in the paper, now consists of three steps: 1. Specification of the data required for the solution of a given problem. 2. Calculating whether vibration isolators are needed. 3. Determining the dynamic properties of the isolation system when the above step indicates isolation mounts are needed.

ENGINE noise has become an increasing problem with the higher and higher compression ratios of present-day automotive engines. Because fuel octane number cannot be raised indefinitely, the problem is one of engine design and selection of crankcase lubricating oils and gasoline formulations, the authors think. This paper describes investigations into the cause of spark knock, wild ping, rumble, and the added problem of hot-spot surface ignition (which also intensifies as compression ratios increase). The authors have found gasolines with phosphorous additives, used with properly formulated multiviscosity lubricating oils, provide a partial answer to the problem of engine rumble. The authors conclude that very exact tailoring of fuels, lubricants, additives, and engines will be necessary to prevent engine noise if compression ratios continue to rise.

TODAY'S high-compression engines present new problems of engine noise to automotive engineers. This paper deals with some of the factors which contribute to rumble, knock, and surface ignition. The work was primarily concerned with the influence of fuel composition on the equilibrium octane number requirement and surface ignition tendency of high-compression engines. Both the effect of the combustion-chamber deposits formed by the fuel and the effect of the combustion characteristics of the fuel itself were considered. The results indicate that a reduction in gasoline tail-end volatility or the use of an effective ignition control additive can reduce knock, surface ignition, and rumble; while use of gasolines containing high concentrations of aromatic hydrocarbons can increase these combustion difficulties.

PAPER DESCRIBES a procedure for the dynamical design of linear vibration isolators to protect a rigid equipment from the sinusoidal motions of a nonrigid supporting structure. A single degree of translational freedom of the equipment is assumed. Three types of data are required: (1) The equipment mass and its so-called fragility curve, (2) the mechanical admittance of the supporting structure and its amplitude of vibration when it supports no load, and (3) information to establish a minimum stiffness of the isolators. The procedure yields a region of permissible natural frequency and fraction of critical damping combinations for the isolator-mass system. The specification for the isolator dynamical requirements, including allowable tolerances, is derived from this region.*

The property owners, an off-highway motor vehicle club, purchased an abandoned quarry to ride off highway motorcycles (OHM's), snowmobiles and all-terrain vehicles (ATV's). The neighbors complained about the noise and tried to stop further riding of recreational vehicles in the quarry. As a result, the town filed a lawsuit against the property owners, citing several zoning code violations, including the fact that the property owners did not obtain a conditional-use permit, which the zoning ordinance requires for any use of the property. This paper reviews the Wisconsin Supreme Court ruling finding the zoning ordinance unconstitutional because there were no permitted uses of the property, just several conditional uses. As written at that time, owners of property within this zoning classification could not use their property for any purpose (recreation, hunting, etc.) unless they applied for and obtained a conditional-use permit.

Zero-offset in transducer output during airbag noise testing is often observed, but mostly ignored due to the lack of understanding of its causes and implications. In the field of high-g acceleration measurement, this phenomenon is well documented, and is referred to as zeroshift. Zero-offset occurs when a component in the measurement chain is exposed to some unexpected inputs which the component has not been designed to handle. These unexpected inputs can be mechanical, electrical, or optical. How the transducer reacts to such inputs and the amount of zero-offset produced depends on the sensing mechanism, material used, and the design of the component itself. This paper explores the causes of zero-offset from a general perspective, covering the entire measurement chain. Although much of the information and discussions are based on data obtained from acceleration measurement systems, the findings are applicable to other transducer types, such as pressure and acoustic measurements.