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Squeak and rattle (S&R) problems in body structure and trim parts have become serious issues for automakers because of their influence on the initial quality perception of consumers. In this study, various CAE and experimental methods developed by Hyundai Motors for squeak and rattle analysis of door systems are reported. Friction-induced vibration and noise generation mechanisms of a door system are studied by an intelligent combination of experimental and numerical methods. It is shown that the effect of degradation of plastics used in door trims can be estimated by a numerical model using the properties obtained experimentally. Effects of changes in material properties such as Young's modulus and loss factor due to the material degradation as well as statistical variations are predicted for several door system configurations. As a new concept, the rattle and squeak index is proposed, which can be used to guide the design.

In diesel engine development, fuel consumption, emissions and combustion noise have been main development objectives for fuel economy, low emissions and NVH. These main objectives can be achieved with advanced engine technologies. As electronic actuating systems are widely applied on diesel engines, elaborate control is required. This is because the main development targets are greatly affected by engine control parameters but frequently have a trade-off relationship. Therefore, the optimization of combustion control parameters is one of the most challenging tasks for improvement. As an efficient method, the DOE methodology has been used in engine calibration. In order to develop a mathematical model, the input and output values must be measured. Unlike other variables, combustion noise has been continually reported to have better indication method in simplified way. In this paper, advanced noise index from cylinder pressure signal is applied on engine test.

A new approach to achieve better customer perception of overall vehicle quietness is the sound balance improvement of vehicle interior sound during driving. Interior sound is classified into 3 primary sound source shares such as engine sound relative to revolution speed, tire road noise and wind noise relative to vehicle speed. Each interior sound shares are classified using the synchronous time-domain averaging method. The sound related to revolution order of engine and auxiliaries is considered as engine sound share, tire road noise and wind noise shares are extracted by multiple coherent output power analysis. Sound balance analysis focuses on improving the relative difference in interior sound share level between the 3 primary sound sources. Virtual sound simulator which is able to represent various driving conditions and able to adjust imaginary sound share is built for several vehicles in same compact segment.

This paper describes a systematic approach to the development of a luxurious driving sound. In the first step, the luxurious sound is conceptualized through jury test, factor analysis and regression analysis. From the results, the main factors and the correlation equation for the luxurious sound are extracted. Also, customer's preference for the luxurious sound is investigated from the customer clinic. In the second step, three core axes and the detailed indices for luxurious sound are defined and quantified. These core axes are a dynamic sound character, a sound balance and a sound harmony. These core axes are also composed of detailed indices and quantified by guide lines. In the third step, each contribution of the sub-systems for sound quality is identified and the target values and methods for implementing the luxurious sound are suggested. In this process, noise path analysis and the customer's preference in each region are considered.

Creep groan noise occurs in a just moving vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure in-vehicle. It is the low frequency noise giving the driver a very uncomfortable feeling. It is caused by the stick-sleep phenomenon at the lining and disc interface. Recently, the field claim of low frequency creep groan has increased. There are a lot of efforts to improve creep groan noise by means of modification of lining material. In this paper, Transfer path of creep groan noise was analyzed through ODS and TPA. Additionally the correlation between Source (Brake torque variation, Brake vibration) and Creep Groan Sound level was discussed. Finally countermeasure to Creep Groan noise was suggested.

Identification of structure borne sound sources induced by the structural vibration of an automotive powertrain has been studied. Based on the principal component analysis which uses singular value decomposition of a matrix consisting of the auto- and cross-spectra, the operating vibrational analysis is performed. The quantitative description of the output power due to intrinsic incoherent source is addressed. The applicability of the technique is tested both numerically and experimentally. First, the coherence analysis is numerically carried out with a simple structure which is modeled as multi-input and single output to identify the structure borne noise generation process. Second, the actual vibrational behavior of a powertrain structure and the interior noise analysis of a car under the running condition are carried out. The technique is shown to be very effective in the identification of the structure borne noise sources.

Acoustics comfort is a key point for the ground transportation market and in particular in the automotive area. A significant contributor to the noise levels in the cabin in the range 200Hz to 3000Hz is the HVAC (Heating, Ventilating, and Air Conditioning) system, consisting of sub-systems such as the air intake duct, thermal mixing unit, blower, ducts, and outlet vents. The noise produced by an HVAC system is mainly due to aeroacoustics mechanisms related to the flow fluctuations induced by the blower rotation. The structure borne noise related to the surface induced vibrations and to the noise transmission through the dash or plastic panels may also contribute but is not considered in this study. This study presents a digital approach for HVAC aeroacoustics noise predictions related to the ducts and outlet vents. In order to validate the numerical method flow and acoustics measurements are performed on production HVAC systems placed in an anechoic room.

This paper presents the design of an additional structure based on acoustic metamaterial (AMM) for the reduction of vibro-acoustic transfer function of a car body panel. As vehicles are lighter and those engine forces are bigger recently, it has become more difficult to reduce the vibration and noise transfer through body panels by using just conventional NVH countermeasures. In this research, a new approach based on AMM is tried to reduce the vibration and noise transfer of a firewall panel. First, a unit cell structure based on the locally resonant metamaterial is devised and the unit cell’s design variables are studied to increase the wave attenuation in the stop band of a dispersion curve, where the Floquet-Bloch theorem is used to estimate the dispersion curve of a two-dimensional periodic structure. Also, the vibration transfer and the vibro-acoustic transfer are predicted in a FE model of meta-plate which is composed of a periodic system of the devised unit cell.

Brake grinding noise is caused by the friction of the disc and pads. The friction generates vibration and it transmits to the body via the chassis system. We called it structure-borne noise. To improve the noise in the vehicle development, the aspects of chassis or body's countermeasure occurs many problems, cost and time. In this reason many brake companies try to make solution with brake system, like brake pad materials or disc surface condition. However the countermeasures of excitation systems also have a lot of risk. It could be occurred side-effects of braking performance, and need to re-verify brake noise like Creep-groan, Groan, Squeal, Judder and so on. For this reason, it is essential to make a robust chassis system in the initial development stage of the vehicle for the most desirable grinding noise-resistant vehicle. This paper is about rear brake grind noise path analysis and countermeasure of chassis system. There are two steps to analysis.

Voice Recognition (VR) systems have become an integral part of the infotainment systems in the current automotive industry. However, its recognition rate is impacted by external factors such as vehicle cabin noise, road noise, and internal factors which are a function of the voice engine in the system itself. This paper analyzes the VR performance under the effect of two external factors, vehicle cabin noise and the speakers’ speech patterns based on gender. It also compares performance of mid-level sedans from different manufacturers.

Faced with the challenge to improve vehicle quality and reduce the development cycle for new product, experimental and/or analytical approach have been used to assure improvements in vehicle NVH performance. Prediction of dynamic characteristics is the most important factor to shorten development time. In order to predict car interior noise at the pre-design stage, a total vehicle without chassis parts and its cavity are fully modeled by finite elements. To reduce FE model generation time and get more effective design modification index, hybrid model combining FE data and experimental data is used. In this paper, the hybrid modeling based on FBS technique is used for identifying substructure contribution and modification. Driving force is also acquired by powertrain test. To verify this model, a passenger car is tested and compared with analysis data.

The purpose of this paper is to identify and reduce the suspension rattle noise. First, the characteristics of the rattle noise are analyzed experimentally in the time and frequency domain. It was found that the rattle noise and vibration at shock absorber mounting point are strongly correlated. Second, the sensitivity analysis of design parameters is performed using a half car model in ADAMS. The result of the simulation model is verified by comparison with test. Finally, the influence of design parameters for the rattle noise is investigated. The study shows that the shock absorber mounting bushing is the most sensitive parameter to affect the suspension rattle noise. This paper shows how the suspension rattle noise can be improved.

Squeak and rattle (S&R) noises are undesirable noises caused by friction-induced vibration or impact between surfaces. While several computer programs have been developed to automatically detect and rate S&R events over the years, no reported work has been found that can detect squeak and rattle noises and distinguish them. Because the causes of squeak noises and rattle noises are different, knowing if it is a squeak noise or rattle noise will be very helpful for automotive engineers to choose an appropriate measure to solve the problem. The authors have developed a new algorithm to differentiate squeak noises and rattle noises, and added it to the S&R detection algorithm they had developed previously. The new algorithm utilizes a combination of sound quality metrics, specifically sharpness, roughness, and fluctuation strength.

As the original engine sound is usually not enough to satisfy the driver’s desire for a sporty and fascinating sound, Active Noise Control (ANC) and Active Sound Design (ASD) have been great technologies in automobiles for a long time. However, these technologies which enhance the sound of vehicles using loud speakers or electromagnetic actuators etc. lead to the increase of cost and weight due to the use of external amplifiers or actuators. This paper presents a new technology for generating a target sound by the active control of a permanent magnet synchronous motor (PMSM) of a mass-production steering system. The existing steering hardware or motor is not changed, but only additional software is added. Firstly, an algorithm of this technology, called Active Sound Generation (ASG), is introduced which is compiled and included in the ECU target code. Then the high frequency noise issue and its countermeasures are presented.

This paper presents an energy-optimal deceleration planning system (EDPS) to maximize regenerative energy for electrified vehicles on deceleration events perceived by map and navigation information, machine vision and connected communication. The optimization range for EDPS is restricted within an upcoming deceleration event rather than the entire routes while in real time considering preceding vehicles. A practical force balance relationship based on an electrified powertrain is explicitly utilized for building a cost function of the associated optimal control problem. The optimal inputs are parameterized on each computation node from a set of available deceleration profiles resulting from a deceleration time model which are configured by real-world test drivings.

Fluctuation in the sound pressure level of the interior noise of an on-road vehicle is always caused by unpredictable factors such as wind gusts, traffic, roadside obstacles, and changing drive-by-drive conditions, and is hence, not reproducible in nature. Since the human brain is known to be more sensitive to noise that is amplitude-modulated than noise at a steady level [1], it is important to evaluate and improve the NVH performance of a vehicle in terms of the fluctuating interior noise likely to be experienced by drivers or users. To this end, an evaluation system was developed as part of this study, the details of which are presented in this paper. The system is composed of hardware for database storage and replay of sounds, and software for synthesizing the noise signals. For given wind tunnel test results, the evaluation system yields a wind noise model that can synthesize wind noise signals for any wind scenario.

This paper describes more in detail the methodology, the measurements and the results of the ASQ method. The Airborne Sound Quantification method aims at identifying the acoustical contribution of the different body panels surrounding a cavity. The contribution of different body panels is the product of the acoustical strength (or volume velocity) of each panel with the corresponding acoustic transfer function between the panel and the interior microphone position. These volume velocities are the product of the corresponding normal velocity and the surface. The normal velocity has been measured by means of accelerometers attached to the different subpanels. In the next step, the acoustical FRF's are measured in an indirect way using the reciprocity principle. This means that the pressure response at all the subpanels is measured when the acoustical excitation takes place at the target interior noise microphone position. A high quality low frequency sound source has been used.

This paper shows the cause and the solution to the uncommon noise which happens ½ order component of engine rpm when a vehicle with automatic transmission has an air conditioning load and “drive” range load on the engine. By measuring cylinder pressure, main bearing cap vibration, engine mount vibration, and interior noise simultaneously, the cause of the noise can be proved by analyzing and comparing the data. The cause of the uncommon noise is bending vibration of the crank shaft. To solve the problem, one can change the crank shaft dynamics by reducing the mass of the damper pulley.

A comprehensive investigation was carried out in order to develop the idle sound quality for diesel V6 engine when the engine development process is applied to power-train system, which included new 8-speed automatic transmission for breaking down the noise contribution between the mechanical excitation and the combustion excitation. First of all, the improvement of dynamic characteristic can be achieved during the early stages of the engine development process using experimental modal analysis (EMA) & the robust design of each engine functional system. In addition, the engine structural attenuation (SA) is enhanced such that the radiated combustion noise of the engine can be maintained at a target level even with an increased combustion excitation. It was found that the engine system has better parts and worse parts in frequency range throughout the SA analysis. It is important that weak points in the system should be optimized.

The sliding surface of the brake friction material is not uniform but composed of random contact plateaus with a broad pressure distribution, which are known to closely related to the triggering mechanism of friction induced noise and vibrations. The non-uniform contact plateaus are attributed to the various ingredients in the friction material with a broad range of physical properties and morphology and the size and stiffness of the plateau play crucial roles in determining the friction instability. The incorporation of friction surface inhomogeneity is, therefore, crucial and has to be counted to improve the accuracy of the numerical calculation to simulate brake noise. In this study, the heterogeneous nature of the friction material surface was employed in the simulation to improve the correlation between numerical simulations and experimental results.