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High frequency wind noise caused by turbulent flow around the front pillars of a vehicle is an important factor for customer perception of ride comfort. In order to reduce undesirable interior wind noise during vehicle development process, a calculation and visualization method for exterior wind noise with an acceptable computational cost and adequate accuracy is required. In this paper an index for prediction of the strength of exterior wind noise, referred to as Exterior Noise Power (ENP), is developed based on an assumption that the acoustic power of exterior wind noise can be approximated by the far field acoustic power radiated from vehicle surface. Using the well-known Curle’s equation, ENP can be represented as a surface integral of an acoustic intensity distribution, referred to as Exterior Noise Power Distribution (ENPD). ENPD is estimated from turbulent surface pressure fluctuation and mean convective velocity in the vicinity of the vehicle surface.

When vehicles run on the flooded road, water enters to the engine compartment and sometimes reaches the position of the air intake duct and electrical parts and causes the reliability problems. Numerical simulation is an effective tool for this phenomenon because it can not only evaluate the water level before experiment but also identify the intrusion route. Recently, the gap around the engine cooling modules tends to become smaller and the undercover tends to become bigger than before in order to enhance the vehicle performance (e.g., aerodynamics, exterior noise). Leakage tightness around the engine compartment becomes higher and causes an increase of the buoyancy force from the water. Therefore the vehicle attitude change is causing a greater impact on the water level. This paper describes the development of a water level prediction method in engine compartment while running on the flooded road by using the coupled multibody and fluid dynamics.

This paper presents a modeling method for prediction of low-frequency road noise in a steady-state condition where rotating tires are excited by actual road profile undulation input. The proposed finite element (FE) tire model contains not only additional geometric stiffness related to inflation pressure and axle load but also Coriolis force and centrifugal force effects caused by tire rotation for precise road noise simulation. Road inputs act on the nodes of each rib in the contact patch of the stationary tire model and move along them at the driving velocity. The nodes are enforced to displace in frequency domain based on the measured road profile. Tire model accuracy was confirmed by the spindle forces on the rotating chassis drum up to 100Hz where Coriolis force effect should be considered. Full vehicle simulation results showed good agreement with the vibration measurement of front/rear suspension at two driving velocities.

In this paper, the authors introduce the spark plug for misfire detection system by ion current. In order to realize high accuracy misfire detection, the signal of ion current must be larger than that of noise. For maintaining ion signal in all designed lifetime, the configuration and initial condition of spark position are derived by an experiment and consideration about degradation in use. Additionally, the cause of noise is determined by an observation and a theoretical study, and we indicate the method to inhibit noise efficiently. Finally, effect of the methods found by these two approaches is confirmed with an engine, and we propose specifications of spark plug satisfying the condition that realize high accuracy detection by ion current.

For a luxury sedan, quietness is a major selling point, and a hybrid luxury sedan is expected to be especially quiet. Therefore, in the development of the hybrid luxury sedan, every possible effort is needed to reduce the hybrid system noise in order to ensure a level of quietness far superior to that of an ordinary gasoline-powered vehicle. In addition, the noise and vibration phenomena that are particular to vehicles with longitudinal power trains require special reduction technologies. This paper first describes the superior quietness of hybrid luxury vehicles in comparison with ordinary gasoline-powered vehicles. This paper then addresses the development issues of vibration during engine starting, engine booming noise, and motor noise, explaining the mechanisms by which they are generated and the technologies employed to reduce them.

It is difficult to improve tire cavity noise since the pressure of cavity resonance acts as a compelling force, and its low damping and high gain characteristics dominate the vibration of both the suspension and body. For this reason, the analysis described in this article aimed to clarify the design factors involved and to improve this phenomenon at the source. This was accomplished by investigating the acoustic coupling vibration mode of the wheel, which is the component that transmits the pressure of cavity resonance at first. In addition, the vibration characteristic of suspension was investigated also. A speaker-equipped sound pressure generator inside the tire and wheel assembly was developed and used to infer that wheel vibration under cavity resonance is a forced vibration mode with respect to the cavity resonance pressure distribution, not an eigenvalue mode, and this phenomenon may therefore be improved by optimizing the out-of-plane torsional stiffness of the disk.

Whinning gear noise(final gear noise), one of the causes for automobile interior noise is due to the exciting force of final gear kit and as a general countermeasure for this problem, a reduction of resonance level in transfer system and better meshing of gears have been utilized. However,vibration characteristics of final gear unit have not been considered much in this case. Authors have executed impacting test on final gear unit and confirmed its vibration characteristics. Based on this fact,vibration model consisting of bearings and gears spring system was constructed to evaluate vibration characteristics of final gear unit along with the results obtained from final gear unit of front engine,rear drive passenger car.

Continuously variable transmission (CVT) and hybrid systems, which have metal belts and electrical units not found in conventional transmissions, are susceptible to extremely High Frequency belt and electromagnetic noise between 5 to 10 kHz. The evaluation and reduction of high frequency (HF) noise of 5 kHz and more is therefore a critical point for improving the quietness of vehicles installed with such systems. This article describes new sound source search technology capable of identifying sources of noise up to 15 kHz in the vehicle interior. Unlike conventional beamforming methods, this new system uses an improved microphone array provided with additional acoustic material. This article outlines the development of the system and its application to sound source identification of HF noise in a hybrid vehicle.

In this study, a new practical design method (tool) for engine sound quality in a car interior is proposed. The tool can automatically create the target interior sound using the psychoacoustic index ‘powerfulness’ based on subjective tests. Moreover, it can calculate the intake noise characteristic to create the target interior sound and select the suitable intake specification from the prepared database. By using this method sound engineering can be easily and effectively carried out without manufacturing an experimental car.

The world's first mass production gasoline hybrid passenger car, the “Prius”, was introduced into the Japanese market in 1997. By the time it was introduced into the American and European markets in Mid-2000, its fuel consumption and exhaust emissions had been further improved while achieving superior NV performance compared with conventional vehicles with 1.5-liter engines even in these competitive markets. This paper describes NV reduction technology for problems peculiar to the hybrid vehicle such as engine start/stop vibration, drone noise and vibration at low engine speed and motor/generator noise and vibration. It also compares the overall NV performance of the hybrid vehicle with conventional gasoline engine vehicles.

This paper describes and discusses the result of a comprehensive simulation analysis we have carried out to clarify the effects of gear dimensions, tooth surface modification, and manufacturing error on the static transmission error of automotive hypoid gears. Three representative factors have been analyzed contact ratio, crowning and pitch error because these characteristics play the most important role in tooth dimensions, tooth surface modification and manufacturing error. The analysis has clarified the effect of each factor on gear noise, making it possible to prepare a guideline for optimal design of gear dimensions and tooth surface modification under various conditions.

Statistical Energy Analysis (SEA) is a promising tool for developing an efficient sound package design for reducing airborne interior noise at high frequencies. The optimal sound package, however, is not directly predicted by using the SEA vehicle model alone and therefore requires parametric studies of sound package configurations. This paper describes an effective method for using SEA modeling to achieve the desired interior noise level targets. A mathematical model, expressed by one equation, is derived on the assumption that the directions of the power flows are known in the SEA model. This equation describes the relationship between sound package properties and the resulting interior noise level. Using the relationship between weight and performance of sound package, an efficient configuration can be determined. The predicted sound pressure level of the vehicle interior with the optimized sound package correlated well to the experimental data for the case presented in this paper.

Weight reduction and high transmission efficiency demands are getting heavier to manual transmission (MT) for vehicle driving and fuel economy performance. Also comfortable shift feeling and low gear noise level are continuously required by customer because those sensitivity performances are directly recognized by driver which can determine the transmission's merchantability. Newly developed high torque capacity MT is based on serial transmission BG6 which is adopted into a lot of customer' vehicle. This new MT is weight reduced, shift feeling and gear noise performance are highly improved that keeps strong competitiveness in the future. Concerning shift feeling, its smoothness, force balance and cross shift performance are improved and optimized. Also for low gear noise performance, it was reduced to the level which can have advantage to competitor and highly comfortable for passenger vehicle. Those improvement technologies are reported as follows.

The renewed platform of the upcoming flagship front-engine, rear-wheel drive (FR) vehicles demands high levels of driving performance, fuel efficiency and noise-vibration performance. The newly developed driveline system must balance these conflicting performance attributes by adopting new technologies. This article focuses on several technologies that were needed in order to meet the demand for noise-vibration performance and fuel efficiency. For noise-vibration performance, this article will focus on propeller shaft low frequency noise (booming noise). This noise level is determined by the propeller shaft’s excitation force and the sensitivity of differential mounting system. In regards to the propeller shaft’s excitation force, the contribution of the axial excitation force was clarified. This excitation force was decreased by adopting a double offset joint (DOJ) as the propeller shaft’s second joint and low stiffness rubber couplings as the first and third joints.

To reduce interior noise effectively in the vehicle body structure development process, noise and vibration engineers have to first identify the portions of the body that have high sensitivity. Second, the necessary vibration characteristics of each portion must be determined, and third, the appropriate body structure for achieving the target performance of the vehicle must be realized within a short development timeframe. This paper proposes a new method based on the substructure synthesis method which is effective up to 200Hz. This method primarily utilizes equations expressing the relationship between driving point inertance change at arbitrary body portions and the corresponding sound pressure level (SPL) variation at the occupant's ear positions under external force. A modified system equation was derived from the body transfer functions and equation of motion by adding a virtual dynamic stiffness expression into the dynamic stiffness matrix of the vehicle.

Brake squeal is a phenomenon of self-induced vibration of the brake components during braking. There are many kinds of brake squeal cases whose mechanisms require acting on a various number of potential root causes. Brake squeal phenomena can be generally separated into 2 main mode types related to the direction of disc vibration involved: in-plane mode and out-of-plane mode. For out-of-plane mode, a number of existing countermeasures can be potentially applied after characterization of the squeal occurrence condition by direct experiment or simulation analysis[1,2,3,4]. However, as there are many possible mechanisms and root causes for the in-plane modes[5,6,7,8,9,10,11,12,13], it is generally necessary to perform a detailed analysis of the vibration mechanism before implementing a countermeasure.

Low frequency interior wind noise is typically dominated by underfloor flow noise. The source mechanisms are fluctuating surface pressure loading from both flow turbulence and acoustic field levels developed in the semi-reverberant cavity between floor and road. Previous studies have used computation fluid dynamics (CFD) to estimate the aero-acoustic loading applied to a vibro-acoustic model, which is then used to predict the transmitted interior wind noise. This paper reports a new perspective in two respects. First it uses novel surface pressure microphone arrays to directly measure the underfloor aero-acoustic loading in the wind tunnel. Second, it considers two different underfloor aerodynamic configurations - with and without lightweight aero cover panels, which are installed primarily to reduce aerodynamic drag.

Generally, automobiles have many performance requirements for comfort, of which noise, vibration and harshness are very important. Toyota Motor Corporation equipped several 2003 models with the second-generation Electronically Controlled Brake system (ECB2). These ECB2 actuator units adopted a new structure that reduced pumping noise by controlling the skew phenomena of needle roller bearings. Normally, needle roller bearings are advantageous over other bearings in cases where a large force is loaded on bearings, because the contact areas can be made larger. However, a thrust force arises from skew phenomena because of minute clearances among the component parts of needle roller bearings. As a result, axial vibration of the bearing shaft sometimes occurs due to the thrust force. This paper explains how the thrust force generated from the skew phenomena of needle roller bearings occasionally affects the pumping vibration level of equipped machinery such as the brake actuator unit.

The new gasoline hybrid car, “the Prius”, has achieved both two-liter class power performance and world top-class gas mileage with the new Toyota Hybrid System “THS II”. Compared with the previous THS, the electric motor drive power of the THS II has been boosted by 50% and the weight of this system has been reduced by 20%. This paper describes the NV problems caused by the improvements to the hybrid system, and the countermeasures for them. It also describes the technologies for reduction of engine start vibration. Finally an evaluation method and countermeasures against interior engine noise are described.

It is well known that pilot injection is an effective method of reducing diesel knock noise during idling, but no actual system has as yet been commercially produced. With the objective of developing a practicable pilot injection device, simulations were conducted of various simple mechanisms in order to determine the best specifications and analyze the fuel injection characteristics. Based on these results, a chamber expansion type pilot injection device, which enables the injection pump pressure chamber volume to be increased at a given moment during the fuel compression stroke, has been developed and has been found to remarkably decrease knock noise during cold idling. An investigation into the effects of this device on output power, exhaust emissions, cold startability and durability revealed that it is eminently suitable for practical application.