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SAE 2009 Noise and Vibration Conference and Exhibition
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Application of Tuned Mass Damper to Address Discrete Excitation Away From Primary Resonance Frequency of a Structure

Chrysler LLC-Pari Tathavadekar, Kuang-Jen Liu, Senthil Rajan, Patrick Johnson
Published 2009-05-19 by SAE International in United States
Tuned mass dampers (TMDs) or vibration absorbers are widely used in the industry to address various NVH issues, wherein, tactile-vibration or noise mitigation is desired. TMDs can be classified into two categories, namely, tuned-to-resonance and tuned-to-discrete-excitation. An overwhelming majority of TMD applications found in the industry belong to the tuned-to-resonance category, so much of information is available on design considerations of such dampers; however, little is published regarding design considerations of dampers tuned-to-discrete-excitation. During this study, a problem was solved that occurred at a discrete excitation frequency away from the primary resonance frequency of a steering column-wheel assembly. A solution was developed in multiple stages. First the effects of various factors such as mass and damping were analyzed by using a closed-form solution. Once the initial design guidelines were obtained, prototype parts were built to quantify the in-situ benefit of the damper at the desired frequency. Finally, the effect of production variability was studied by measuring a larger population of randomly selected parts. The findings of the study provide important clues to the utility and…
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Modeling Interior Noise in Off-Highway Trucks using Statistical Energy Analysis

Caterpillar Inc.-Rohit Gujarathi, David Copley, Richard Romick
Michigan Technological University-Mohan Rao
Published 2009-05-19 by SAE International in United States
The objective of this project was to model and study the interior noise in an Off-Highway Truck cab using Statistical Energy Analysis (SEA). The analysis was performed using two different modeling techniques. In the first method, the structural members of the cab were modeled along with the panels and the interior cavity. In the second method, the structural members were not modeled and only the acoustic cavity and panels were modeled. Comparison was done between the model with structural members and without structural members to evaluate the necessity of modeling the structure. Correlation between model prediction of interior sound pressure and test data was performed for eight different load conditions. Power contribution analysis was performed to find dominant paths and 1/3rd octave band frequencies.
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Energy Density Field Approach for Low- and Medium-Frequency Vibroacoustic Analysis of a Car Body Using a Probabilistic Computational Model

PSA-Peugeot-Citroën-Laurent Gagliardini, Morad Kassem
Université Paris-Est-Christian Soize
Published 2009-05-19 by SAE International in United States
In this paper, a new energy-density field approach is proposed for low- medium-frequency vibroacoustic analysis of complex industrial structures, using a probabilistic computational model. The observed structure is composed of a trimmed body coupled and its internal cavity. The objective of this paper is to take advantage of some statistical properties of the frequency response functions to build a simplified vibroacoustic model. In this approach, the Frequency Response Functions (FRF) of the vibroacoustic system are expressed as the product of a dimensionless “smooth” matrix and local mobilities or impedances, depending on their type (acoustical, vibratory or vibroacoustic). The stochastic computational model of the vibroacoustic system is obtained from the reduced mean computational model and is using a nonparametric probabilistic approach. Thus, both the data uncertainties and the model uncertainties are taken into account. The stochastic equations are solved using the Monte Carlo method providing independent realizations of the dimensionless FRF of the vibroacoustic system. The confidence regions around the mean value of both the conventional FRFs and the dimensionless ones are estimated using quantiles. The…
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The Effect of Composite Material Attachment Method on SAE J1400 Transmission Loss Test Results

The Soundcoat Company Inc.-Steven M. Brown, Dan LaForgia
Published 2009-05-19 by SAE International in United States
Composite layered structures of sound absorptive and barrier materials find frequent use in vehicle NVH control. Developmental transmission loss testing of such composite structures often includes both testing of the barrier material alone and testing of the full composite layered structures.This paper reports on an experimental study of how the method of attachment of the absorptive material to the barrier material influences the transmission loss test results for the composite layered structure and thus the time needed to carry out a series of transmission loss tests.
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A PU Probe Array Based Panel Noise Contribution Analysis Whilst Driving

Microflow Technologies and HAN University-Hans-Elias de Bree
Microflown Technologies-Oliver Wolff, Emiel Tijs
Published 2009-05-19 by SAE International in United States
This paper presents new developments on hot wire anemometer based panel noise contribution analysis. The used sensor allows the direct measurement of particle velocity. Some historical remarks are given and the latest developments of the technique are reported.Four steps are required to determine the panel noise contribution of the interior of a vehicle and to visualize the results in 3D.In a first step the probes are positioned on the interior surfaces and their x, y, z coordinates are measured. Based on these data a 3D geometry model is created. The geometry data are acquired using a specially designed 3D digitizer.The second step is a measurement in a certain mode of operation. This step can be done in a laboratory but it is also possible to perform the measurement whilst driving the vehicle on the road. Stationary as well as non stationary running conditions like e.g. run ups are accessible and do not limit the applicability of the method.The third step is the determination of the transfer paths from the panels to a certain listening position.…
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Development of a New Squeak and Rattle Detection Algorithm

SAE International Journal of Passenger Cars - Mechanical Systems

University of Cincinnati-Unnikrishnan Kuttan Chandrika, Jay Kim
  • Journal Article
  • 2009-01-2111
Published 2009-05-19 by SAE International in United States
A new algorithm to detect and to quantify the seriousness of the detected squeak and rattle (S&R) events was developed. A T-F analysis technique called AWT, the Zwicker loudness model and leaky integration are employed to define new concepts we called transient specific loudness time histories and perceived transient loudness time history. The detection threshold of the perceived transient loudness was identified by a clever interpretation of jury test results. The proposed algorithm showed a good promise producing results that are well correlated with the jury tests. The new algorithm developed in this work will be able to automate detection and rating of the S&R events with good accuracy and with minimum possibility of false alarm under normal operating conditions
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Plug-In Hybrid Vehicle Induction Motor Aerodynamic Noise Evaluation

Helwan University-Ahmed A. A. Saad
Published 2009-05-19 by SAE International in United States
Plug-in hybrid vehicles connect to the power grid while parked so they can operate on electricity from the grid as well as on petroleum-based fuel. This distinguishes them in a fundamental way from the plug-less hybrid vehicles currently produced or planned by auto-marker which rely 100% on the petroleum-based fuel. A plug-in hybrid can reduce emissions. However, the aim of this paper is to investigate experimentally the aerodynamic noise performance of a plug-in hybrid vehicle induction motor with the view of evaluation. For this reason, a special test rig was developed to simulate the motor aerodynamic noise source. The results indicate that significant information can be obtained for this source. This can be an effective way to control this generated noise and consequently reduce the vehicle interior and exterior noises and look promising.
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Optimization of Sound Packages for Commercial Vehicles Using Panel Contribution Analysis

Bruel & Kjaer Sound & Vibration Measurement A/S-Andreas Schuhmacher
E-A-R™ Thermal/Acoustic Systems Aearo Technologies, a 3M company-Manuel Sánchez Castillo
Published 2009-05-19 by SAE International in United States
Microphone array-based Panel Contribution Analysis (PCA) is a new technique used for Sound Package design optimization for commercial vehicles. The technique allows for noise control performance and cost optimization.This technique ranks the contribution of fully trimmed structural panels (e.g. floor, roof, etc.) and leaks in a vehicle cabin to the noise levels experienced by a driver while the vehicle is in cruising operation. Often the noise and vibration sources (engine, transmission, exhaust, aerodynamic noise, tires, etc) cannot be easily modified, thus the only practical action to solve noise problems is to design the noise control treatments applied to the vehicle panels. Panels that have a large contribution to the noise levels at the driver's ear are heavily treated with noise control materials, whereas panels with low contribution get little to no treatment.This paper describes a microphone array-based PCA technique, and the results of a successful application of it to optimize the interior noise level performance of a new commercial vehicle. The application results clearly indicated the dominant contributing panels to the sound pressure levels at…
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Attenuation of Vehicle Noise using Different Trunk Insulation Systems

ESI North America-Terence Connelly
Janesville Acoustics-Barry R. Wyerman
Published 2009-05-19 by SAE International in United States
Attenuation of noise from the rear of a vehicle was evaluated for different trunk insulation systems using a combination of poro-elastic material modeling and a full vehicle SEA model. The model considered the interaction between the trunk and the passenger cabin. The sound absorption coefficients and acoustic impedance for each of the material systems used in the trunk were measured and the poro-elastic Biot properties were calculated to define the acoustic treatments in the SEA model. Several levels of acoustical treatment for the trunk were studied ranging from a trunk with no decorative liner to a trunk with a liner and maximum acoustical treatment. The results show the contribution of the trunk material in reducing cabin noise for different levels of noise originating at the rear of the vehicle. These results demonstrate the value of combining poro-elastic material modeling and SEA models for selecting efficient material systems early in a vehicle design. They also highlight vehicle designs that require acoustically tuned trunk material to prevent compromises in the overall NVH performance.
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A Method for Torsional Damper Tuning Based On Baseline Frequency Response Functions

Chrysler LLC-C. Q. Liu
Published 2009-05-19 by SAE International in United States
Based on Woodbury-Sherman-Morrison formula, a general and efficient method for torsional damper tuning is presented. This method is based on exact calculation of the resulting Frequency Response Functions (FRF's) of the system with the damper by using the original (old) FRF's of the original (baseline) system and the damper's parameters (the mass polar moment of inertia, stiffness and damping coefficient). The only requirement for this method is to have the baseline FRF's at the active points of the structure where the damper is to be attached and those point where the resulting FRF's are of interest. The baseline FRF's can be obtained by either analytical or experimental methods. Once this requirement is met, all possible scenarios of the dampers for their potential and feasibility can be efficiently evaluated before being put into service without the need for costly hardware modification and test cycles on actual structure. As such, a considerable amount of engineering time and effort can be saved.
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