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In this paper an alternative engineering solution to control vehicle steering wheel vibration is presented. The strategy is focused on the implementation of an effective tuned vibration absorber which also complies with time frame and costs requisites. The vibration levels in this case study are enhanced due resonances in the chassis frame and steering column. The tuned mass damper is basically a suspended mass attached on a vulcanized rubber body, aiming for the customer benefits; this solution can be classified as low cost as well low complexity for implementation. In this case study, a mid-size truck was used as a physical hardware and the data were collected through accelerometers on the steering wheel and other critical components. As a control factor, different tunings on different parts were applied to optimize the auxiliary system performance and robustness.

Sound absorption materials can be key elements for mass-efficient vehicle noise control. They are utilized at multiple locations in the interior and one of the most important areas is the roof. At this location, the acoustic treatment typically comprises a headliner and an air gap up to the body sheet metal. The acoustic performance requirement for such a vehicle subsystem is normally a sound absorption curve. Based on headliner geometry and construction, the sound absorption curve shape can be adjusted to increase absorption in certain frequency ranges. In this paper an overall acoustic metric is developed to relate design parameters to an absorption curve shape which results in improved in-vehicle performance. This metric is based on sound absorption coefficient and articulation index. Johnson-Champoux-Allard equivalent fluid model and diffuse field equations are used. The results are validated using impedance tube measurements.

It is known acoustic comfort is a key feature to meet customer expectations for many products. In the current automotive industry, vehicle interior quietness is seen as one of the most important product attributes regarding perceived quality. A quiet interior can be achieved through an appropriate balance of noise sources levels and acoustic materials. However, the choice of the most efficient acoustic content may be challenging under severe cost and mass restraints commonly found in emerging market vehicles. Therefore, it is fundamental to develop efficient materials which will provide high acoustic performance with lower weight and cost. In this paper the fine tuning of the headliner structure is presented as an efficient way to increase acoustic performance. Structures currently employed for this vehicle subsystem are described. Airflow resistance and sound absorption measurements are used to guide development and make precise manufacturing process changes.

Microphone array based techniques have a growing range of applications in the vehicle development process. This paper evaluates the use of Spherical Beamforming (SB) to investigate the transmission of wind-generated noise into the passenger cabin, as one of the alternative ways to perform in-vehicle troubleshooting and design optimization. On track measurements at dominant wind noise conditions are taken with the spherical microphone array positioned at the front passenger head location. Experimental diligence and careful processing necessary to enable concise conclusions are briefly described. The application of Spherical Harmonics Angularly Resolved Pressure (SHARP) and the Filter-And-Sum (FAS) algorithms is compared. Data analysis variables, run-to-run repeatability and system capability to identify design modifications are studied.

The control of noise and vibrations using conventional damping materials is typically associated to mass penalties in a vehicle. A lightweight alternative employs piezoceramic materials connected in series to a resistor and an inductor (R-L circuit) to perform as mechanical vibration absorber, called piezoelectric resonator. In this paper, piezoelectric resonators are designed to attenuate vibration in a vehicle panel. The choice of design parameters, such as correct placement for the piezoelectric patches and the optimal electrical circuit values, is assisted by Finite Element simulation (FE) and theoretical analysis. Measurements of Sound Transmission Loss (STL) and modal analyses are conducted to demonstrate the efficiency of the proposed technique when compared to a conventional damping material.

Currently, acoustic holography and beamforming are consolidated Noise Source Identification (NSI) techniques with expanding applications. These two microphone array based techniques can provide detailed sound field visualization. Even in enclosed space, such as a vehicle cabin, the sound field can be visualized using Spherical Harmonics Beamforming (SHB). Also, sound radiation from geometrically complex surfaces can be captured with conformal mapping using Statistically Optimized Near-field Acoustic Holography (SONAH). In this paper, an integrated approach using both techniques is presented as a manner to improve sound insulation during a vehicle development. Both vehicle and component level measurements are employed in order to identify the dominant sound transmission paths and add the appropriate acoustic treatments. It is shown that spherical beamforming and conformal mapping are powerful tools which expedite troubleshooting and allow vehicle acoustic content optimization.

Currently, the use of numerical and analytical tools during a vehicle development is extensive in the automotive industry. This assures that the required performance levels can be achieved from the early stages of development. However, there are some aspects of the vibro-acoustic performance of a vehicle that are rarely assessed through numerical or analytical analysis. An example is the modeling of sound transmission through vehicle sealing systems. In this case, most of the investigations have been done experimentally, and the analytical models available are not sufficiently accurate. In this paper, the modeling of the sound transmission through a vehicle door seal is presented. The study is an extension of a previous work in which the applicability of the Hybrid FE-SEA method was demonstrated for predicting the TL of sealing elements.

During the last decades, the application of noise control treatments in vehicles has targeted the main noise transmission paths to interior noise. These paths include vehicle body panels such as dash panel, doors and floor. Many improvements have been achieved on these areas, and, as a consequence, other transmission paths once thought as secondary became relevant. This is the case of the sound transmission through door seals and others sealing elements at mid and high frequencies. In this paper, the interest lies on the prediction of the transmission loss of door seals. A full nonlinear deformation/contact analysis is used to estimate the deformed geometry of a door seal in real conditions. The geometry is then used in a vibro-acoustic analysis to predict the in-situ transmission loss of the seal using a local Hybrid FE-SEA model. The channel between the door and the car structure where the seal is located is also included in the analysis.

Noise generated during tire/road interaction has significant impact on the acoustic comfort of a vehicle. One of the most common approaches to attenuate road noise levels consists on the addition of mass treatments to the vehicle panels. However, the acoustic performance of sealing elements is also relevant and has an important contribution to the noise transmission into the vehicle interior. In this paper the correct balance between the mass added to treat vehicle panels and sealing content is investigated. The procedure to quantify the critical road noise transmission paths consists of recording interior noise levels as applied treatment is removed from potential weak areas, such as wheelhouses, floor, doors and body pillars. It is observed that the noise propagation through body pillars has a direct influence on road noise levels.

A balanced approach for wind noise control is presented in this paper. This approach is focused on improved sound insulation and low mass. Initially, the Sound Transmission Loss (STL) of tempered, standard laminated and acoustic laminated glasses for different thicknesses was measured in a STL suite. The critical frequency range was identified from in-vehicle noise measurements. These STL data and in-vehicle results provided the relevant information for a proposal with better acoustic performance and lower mass. The efficiency of this proposal was confirmed with new in-vehicle measurements.

In this work the acoustic treatment of an engine cover was designed based on airflow resistance and sound absorption data. Single layer and multilayer treatments with measured airflow resistance were employed to reduce noise radiated by a diesel engine. The analysis was focused in the region in which the “knocking” noise is particularly noticeable. The methodology of acoustic design was confirmed by in-vehicle noise measurements. The application of a sound absorption treatment with a controlled specific airflow resistance provided the highest noise attenuation. An improvement in the sound quality was also achieved due to a reduction in the “knocking” noise.

In the last decades, there has been an increasing demand for vehicle noise control and, at the same time, fuel economy has become critical for the automotive industry. Therefore, a precise balance between performance and mass of sound package components is essential. In this work the original dash insulation system of an automotive vehicle was replaced by a lightweight alternative. The methodology of Statistical Energy Analysis (SEA) was employed to design multilayered fibrous constructions for engine noise control. The results were verified through experimental testing and supported the achievement of vehicle requirements regarding comfort, weight and environment.

Vibration levels of structures can be significantly reduced by adding some damping materials to the vibrating surfaces. The viscoelastic behavior of these materials induces losses of kinetic energy when they undergo cyclic deformation. A good estimate of the damping loss factor is an important design parameter allowing the creation of efficient damping treatments. For Statistical Energy Analysis (SEA) purposes, the damping loss factor is usually estimated through the Power Injection Method (PIM). This paper presents the application of PIM to obtain the damping loss factor of a typical fuselage panel. In this case, the structure under study is a curved ribbed-stiffened panel. Tests are carried out for undamped and damped conditions. The added damping is provided by layers of viscoelastic material attached to the fuselage skin. The results show the applicability of the method for this kind of structure.

The experimental determination of the acoustic properties of sound absorption materials is dependent on numerous factors. The accuracy level in the determination of each property is influenced by, for example, the measurement apparatus and the type of material. The objective of this study is to highlight the main sources of uncertainty in the measurement of properties such as sound absorption coefficient, acoustic impedance, flow resistivity and porosity. The uncertainties of the apparatuses used to measure each property are quantified. Also, the uncertainty of the material heterogeneity is assessed and its individual contribution highlighted. Important aspects of the Standards ASTM C 522 and ISO 10534-2, which contain, respectively, recommendations and procedures for flow resistivity and sound absorption measurements, are discussed. The methodology to calculate the uncertainty of each property is discussed in detail, emphasizing the relevance of each uncertainty source.

Airborne sound transmission through vehicle panels is the main contributor to interior noise in high frequencies. This transmission can be reduced by the application of sound insulation materials. An insulator typically used in the dash panel treatment comprises a porous material layer bonded to a limp dense material. This porous layer dissipates sound energy mainly by viscous effects and reduces sound transmission. An accurate prediction of the insulator performance depends on the porous material model adopted and input material properties. Some simplified models take into account only a single longitudinal wave propagating in the porous medium since it is represented by an equivalent fluid with effective properties. More complex models, based on Biot's theory, also consider waves whose properties are more connected to the porous material frame. In this paper one-wave, two-wave and three-wave models are presented.

This paper studies the transmission loss of bounded double panel lined with poroelastic medium. Hamilton variational principle is used to derive the equation of motion. Kirchhoff hypotheses are assumed for the displacement field of the panel and Biot constitutive equations are used to model the poroelastic core. Resonant and non-resonant sound transmissions are investigated. Equivalent stiffness constants of the panel are presented. The results of the transmission loss based on the derived equation are compared with classical results.