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Examining the noise reduction of a motorcycle, the requirement of an effective method of reducing a drive chain noise has been a pending issue similarly to noise originating from an engine or exhaust system, etc. Through this study, it became clear that the mechanism of chain noise could be classified into two; low frequency noise originated from cordal action according to the degree of chain engagement and high frequency noise generated by impact when a chain roller hits sprocket bottom. An improvement of urethane resin damper shape, mounted on a drive side sprocket, was effective for noise reduction of the former while our development of a chain drive that combined an additional urethane resin roller with an iron roller worked well for the latter. The new chain system that combined this new idea has been proven to be capable of reducing the chain noise to half compared with a conventional system.

Recently, many authors have attempted to represent an automobile body in terms of experimentally derived frequency response functions (FRFs), and to couple the FRFs with a FEA model of chassis for performing a total system dynamic analysis. This method is called Hybrid FEA-Experimental FRF method, or briefly HYFEX. However, in cases where the chassis model does not include the bushing models, one can not directly connect the FRFs of the auto body to the chassis model for performing a total system dynamic analysis. In other cases when the chassis model includes the bushings, the bushing dynamic rates are modeled as constant stiffness rather than frequency dependent stiffness, the direct use of the HYFEX method will yield unsatisfactory results. This paper describes how the FRF's of the auto body and the frequency dependent stiffness data of the bushings can be combined with an appropriate mathematical formulation to better represent the dynamic characteristics of a full vehicle.

The popularity of AWD passenger vehicles presents a challenge to provide car-like drive-train NVH within a relatively small package space. This paper describes a drive-train NVH case study in which analysis and test were used, in conjunction, to solve an NVH problem. Also, it details a systematic process of using the analytical model to identify and resolve similar problems. The particular problem for this case study is a noise and vibration issue occurring at 75 MPH primarily in the middle seat of an all-wheel drive vehicle. Tests indicated that it may be due to propeller shaft imbalance. Analysis results showed good correlation with the tests for that loading condition. Several solutions were identified, which were confirmed by both test and analysis. The most cost-effective of these solutions was implemented.

When the belt contacts a pulley in a pushing belt-type CVT, vibration is generated by frictional force due to rubbing between the individual elements that are components of the belt, which is said to increase wear and noise. The authors speculated that the source of that vibration is misalignment of the secondary pulley and primary pulley V-surfaces. To verify that phenomenon, a newly developed micro data logger was attached to an element of a mass-produced metal pushing V-belt CVT and the acceleration was measured at rotations equal to those at drive (1000 to 2500 r/m). In addition, the results of calculations using a behavior analysis model showed that changes in pulley misalignment influence element vibration, and that the magnitude of the vibration is correlated to the change in the metal pushing V-belt alignment immediately before the element contacts the pulley.

This paper summarizes the development of a predictive vibro-acoustic full vehicle model of a mid-size sedan and focuses on the engineering analysis procedures used to evaluate the design performance related to engine induced noise and vibration. The vehicle model is build up from a mixture of test-based and finite element component models. FRF Based Substructuring is used for their assembly. The virtual car model is loaded by engine forces resulting from indirect force identification. This force-set includes combustion, inertia, piston slap and crank bearing forces, for engine harmonics from 0.5 to 10th order. Such forced response analysis yields vibration levels at every component, at every interface between components, and interior noise predictions. The target is to provide the vehicle NVH manager with the insight required to identify major causes for peak noise levels and to set targets and develop an action plan for every component design team.

In this paper, a newly developed Active Noise Control (ANC) system is introduced, that effectively reduces road noise, which becomes a major issue with electrified vehicles, and that enhances vehicle interior sound levels matching seamless acceleration by electric drive. Conventionally, reducing road noise using ANC requires numerous sensors and speakers, as well as a processor with high computing power. Therefore, the increase in system cost and the complexity of the system are obstacles to its spread. To overcome these issues, this system is developed based on four concepts. The first is a modular system configuration with unified interface to apply to various vehicle types and grades. The second is the integration and optimal placement of noise source reference sensors to achieve both reduction in number of parts and noise reduction performance.

When a vehicle is in motion, noise is generated in the cabin that is composed of noise in multiple narrow-frequency bands and caused by input from the road surface. This type of noise is termed low-frequency-band road noise, and its reduction is sought in order to increase occupant comfort. The research discussed in this paper used feedback control technology as the basis for the development of an active noise control technology able to simultaneously reduce noise in multiple narrow-frequency bands. Methods of connecting multiple single-frequency adaptive notch filters, a type of adaptive filter, were investigated. Based on the results, a method of connecting multiple filters that would mitigate mutual interference caused by different controller transmission characteristics was proposed.

The application of inverter technology has enabled the realization of a lightweight, portable power generator. It produces an 80% duty, square wave alternating current (AC). Protective features are incorporated to safeguard internal transistors and other electrical components, as well as various pieces of electrical equipmemt utilizing the power it produces.

The development of the lightweight and compact EU1000i generator with a maximum output of 1kVA is presented. The technology applied to achieve the required levels of exhaust emission, fuel consumption and noise, and to provide a stable electrical power supply with low waveform distortion is described. The technology comprises of four elements: a high-speed, multi-pole, external rotor type alternator, a microcomputer-controlled sine wave inverter, a compact high-speed 4-stroke engine with electronic speed governing, and a lightweight frame with a two-level noise-damping system. Combination of these four elements of technology has achieved 50% less weight, 25-30% lower fuel consumption, and 7-9dB(A) less noise than the previous model. The emission levels of CO and of NOx + HC are also 30% and 65% lower than the 2000 CARB regulations.

A 50 Hz Solid-State Relay (SSR) was used to provide pulse-width-modulated power to engine cooling fans for continuous speed control, to reduce airflow noise and improve efficiency. However, this caused the cooling fans to vibrate at the switching frequency and harmonics, thus degrading vehicle NVH performance. This paper describes the problem associated with SSR- powered cooling fans, including root-cause analysis, and identification of areas sensitive to vibration affected by the switching power supply. Based on our analysis, we found several solutions to the problem. Our production solution and some generic recommendations for shroud design are presented in the paper.

The process for setting the marketability targets and achievement methods for automotive interior quietness (as related to air borne noise above 400Hz, considered the high frequency range) was established. With conventional methods it is difficult to disseminate the relationship between the performance of individual parts and the overall vehicle performance. Without new methods, it is difficult to propose detailed specifications for the optimal sound proof packages. In order to make it possible to resolve the individual components performance targets, the interior cavity was divided into a number of sections and the acoustic performance of each section is evaluated separately. This is accomplished by evaluating the acoustical energy level of each separate interior panel with the unit power of the exterior speaker excitation. The applicability of the method was verified by evaluating result against predicted value, using the new method, during actual vehicle operation.

This paper deals with low-frequency squeal phenomena generated in floating type of car disc brake units. First, the vibration characteristics of low-frequency squeal (about 2 kHz) were investigated. Here, in order to reproduce the squeal, a bench-test apparatus consisting of an actual automotive disc brake unit was utilized, itself comprising a disc, pad, and caliper. With this, the associated frequency characteristics were experimentally determined. It was found that the squeal is caused by coupled out-of-plane vibration modes among the disc and caliper due to Coulomb friction. As an experimental countermeasure, a dynamic absorber was applied to the leading side or the trailing side of the inner caliper. It was found that squeal can be suppressed when the natural frequency of the dynamic absorber is tuned so as to be near the frequency of the squeal, and that squeal can be suppressed even without viscous damping of the dynamic absorber.

Extensive studies in various technological fields have been conducted to determine the most appropriate engine configuration (arrangement and number of cylinders) for Honda's next-generation compact luxury automobiles. One of the basic concepts incorporated into these models include an ‘exhilarating drive’. Studies in the noise/vibration field disclosed that noise/vibration levels must be reduced while simultaneously realizing linearity in noise/vibration increase. As a result, an in-line five cylinder engine was chosen for this purpose. Additionally, Honda designed a new five-point engine mount system for a longitudinally-mounted engine in its FWD layout. Crankshaft rumbling noise in the in-line five cylinder engine was proven to be caused by crankshaft torsional resonance, as found in previous research of in-line four and six cylinder engines. This noise deteriorates linearity sensation.

Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation. This paper has two objectives: 1) Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined. 2) Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.

In the development of several outside mirror designs for vehicles, a high frequency noise (whistling) phenomenon was experienced. First impression was that this might be due to another source on the vehicle (such as water management channels) or a cavity noise; however, upon further investigation the source was found to be the mirror housing. This “laminar whistle” is related to the separation of a laminar boundary layer near the trailing edges of the mirror housing. When there is a free stream impingement on the mirror housing, the boundary layer starts out as laminar, but as the boundary layer travels from the impingement point, distance, speed, and roughness combine to trigger the transition turbulent. However, when the transition is not complete, pressure fluctuations can cause rapidly changing flow patterns that sound like a whistle to the observer. Because the laminar boundary layer has very little energy, it does not allow the flow to stay attached on curved surfaces.

A technique was created to separate the contributions of combustion noise and mechanical noise to engine noise in the time domain in order to achieve efficient measures for enhancing the sound quality of combustion noise. There is an existing technique based on 1/3 octave band analysis that is known as a method for separating the contributions to engine radiation noise, but this technique cannot provide time-domain data. Therefore, the author has proposed a technique that separates engine radiation noise into combustion noise and mechanical noise in the time domain by finding the combustion noise for each cylinder and calculating its structural response function by considering its real and imaginary components. Results of analysis of actual engine radiation noise with this technique confirmed that combustion noise, which is characterized by strong pulsation, and irregular mechanical noise can be separated in the time domain with good precision.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

A new piston secondary motion analysis has been developed that accurately predicts piston strength and the slap noise that occurs when the engine is running. For this secondary motion analysis, flexible bodies are used for the models of the piston, cylinder and cylinder head. This makes it possible to quantify the deformations and secondary motion occurring in each area of the engine. The method is a coupled analysis of the structure analysis and the multi body dynamics analysis. The accuracy of the results obtained in the new analysis method was verified by comparing them to measurement data of piston skirt stress and piston secondary motion taken during firing. To measure piston skirt stress, a newly developed battery-powered telemetric measurement system was used. The calculation results were close to the measurement results both for stress and for secondary motion from low to high engine speed.

This paper describes the oil-film bearing analysis simulation was utilized for the optimization of pin boss form which reduces a piston-pin noise. It is clear from the mechanism analysis of the piston-pin noise which is the last research that an oil-film flow inside a pin boss is an important factor for pin noise reduction. So, in this research, the oil-film simulation of the piston-pin-boss bearing part was performed using oil-film bearing analysis tool. After setting up the simulation conditions of the oil-film bearing part so that actual pin behavior and high correlativity might be shown, a parameter, effective hydrodynamic angular velocity, and an oil flow rate of change suitable for evaluation of a pin noise were found out. The pin noise in semi floating piston was reduced to the same level as full floating type by applying pin boss form to which each evaluation parameter becomes the optimal to a piston.

In noise and vibration control, damping treatments are applied on panel surfaces to dissipate the energy of flexural vibrations. Presence of damping treatment on the surface of a panel also plays an important role in the resulting vibro-acoustic characteristics of the composite system. The focus of this study is to explore possibilities of reducing the weight of damping treatments by means of perforation without sacrificing performance. The power injection concept from Statistical Energy Analysis (SEA) is used in conjunction with Finite Element Analysis (FEA) to predict the effect of perforated unconstrained layer treatments on flat rectangular panels. Normalized radiated sound power of the treated panels are calculated to assess the effect of varying percentage of perforation on structural-acoustic coupling.