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A multi-point hypoid gear mesh model based on 3-dimensional loaded tooth contact analysis is incorporated into a coupled multi-body dynamic and vibration hypoid gear model to predict more detailed dynamic behavior of each tooth pair. To validate the accuracy of the proposed model, the time-averaged mesh parameters are applied to linear time-invariant (LTI) analysis and the dynamic responses, such as dynamic mesh force, dynamic transmission error, are computed, which demonstrates good agreement with that predicted by single-point mesh model. Furthermore, a nonlinear time-varying (NLTV) dynamic analysis is performed considering the effect of backlash nonlinearity and time-varying mesh parameters, such as mesh stiffness, transmission error, mesh point and line-of-action. Simulation results show that the time history of the mesh parameters and dynamic mesh force for each pair of teeth within a full engagement cycle can be simulated.

Current powertrain active noise control (ANC) systems are not sufficient enough to track the fast engine speed variations, and yield consistent convergence speeds for individual engine order such that a balanced noise reduction performance can be achieved over a broad frequency range. This is because most of these ANC systems are configured with the standard filtered-x least mean squares (FxLMS) algorithm, which has an inherent limitation in the frequency-dependent convergence behavior due to the existence of secondary path model (electro-acoustic path from the input of control loudspeaker to the output of monitoring error microphone) in the reference signal path. In this paper, an overview is given first to compare several recently modified FxLMS algorithms to improve the convergence speed for harmonic responses such as eigenvalue equalization FxLMS (EE-FXLMS) and normalized reference LMS (NX-LMS) algorithms.

Active noise control systems have been gaining popularity in the last couple of decades, due to the deficiencies in passive noise abatement techniques. In the future, a novel combination of passive and active noise control techniques may be applied more widely, to better control the interior sound quality of vehicles. In order to maximize the effectiveness of this combined approach, smarter algorithms will be needed for active noise control systems. These algorithms will have to be computationally efficient, with high stability and convergence rates. This will be necessary in order to accurately predict and control the interior noise response of a vehicle. In this study, a critical review of the filtered-x least mean square (FXLMS) algorithm and several other newly proposed algorithms for the active control of vehicle powertrain noise, is performed. The analysis examines the salient features of each algorithm, and compares their system performance.

The analytic wavelet transform (AWT) is a wavelet transform that works much like a transient Fourier transform. Therefore the AWT enables utilizing advantages of both the wavelet transform and Fourier transform. A special form of AWT developed for transient vibration and acoustics signal analyses is applied to various engineering signals in this paper. Application examples include a general time-frequency (T-F) analysis, analysis of exposures to impulsive vibrations and noises, and estimation of reverberation times. Some new definitions such as the T-F noise reduction and frequency weighted time history are defined by taking the advantage of unique capabilities of the AWT. Possible automotive applications of these new concepts are briefly discussed.

Acoustically absorptive liners are used in the inlet and exhaust ducts of commercial aircraft engines. A double layer acoustic liner consists of a porous face sheet, a porous septum, an impervious back sheet, and a honeycomb structure. The Acousti-Cap™ technology, developed by Hexcel Corporation, is a significant innovation in the manufacture of double layer acoustic liners. It consists of a non-metallic permeable cap material embedded into each cell of the honeycomb core to create an acoustic septum. This paper presents details of the extensive acoustic testing and analysis carried out to support the development of acoustic liners with embedded mesh-caps.

Sound transmission through a cylindrical double-walled shell lined with an elastic porous material is studied. Love's equation is applied to describe the shell motions coupled with acoustic wave equations. An interesting method is developed to simplify the analysis of the wave propagation in the elastic porous material, which reduces the model developed by Bolton et al. [2] based on the Biot's theory [1] to a simple one-dimensional wave propagation model. The results from the simplified model are compared with those from the Bolton's model and measurements. Solutions for the sound transmission through the cylindrical double-walled shell lined with an elastic porous material are obtained for various configurations using the simplified method, and compared with measured results. Advantages and limitations of the simplified analysis method developed are explained from the perspective of practical applications.

Automobile brake squeal has been experimentally studied in many ways over the past 65 years. A large body of published research and a substantial amount of unpublished work have attempted to experimentally define the variables involved with and describe the system dynamics initiating the friction-induced self-excited vibration. Much of this work has centered on pin on disk type test rigs used to characterize the contact mechanics and/or friction laws without considering the brake system influence. This paper describes a dynamometer designed and constructed to study brake squeal on a system level.

This paper is intended to describe some of the advances in automotive NVH research and applications based on recent developments in the Structural Dynamics Research Laboratory (SDRL) at the University of Cincinnati. State-of-the-art vibro-acoustic research capabilities and infrastructure ranging from advanced vibration modal analysis and spectral techniques for linear and nonlinear automotive systems to computational tools for structure-borne acoustic noise generation, transmission and synthesis problems are discussed. These systems have been devised with the intent of integrating a versatile set of experimental, computational and analytical approaches in order to be able to investigate a variety of crucial automotive NVH concerns. The materials will be grouped into three separate but closely related sets of applications consisting of (i) powertrain noise and vibration control, (ii) analysis and control vehicle system dynamics, and (iii) NVH and sound quality.

Efforts have been made to utilize Al constructs to identify flaws in the Space Shuttle Main Engine (SSME) faceplate regions. In order to expand the applicability of these algorithms to a larger problem domain, the automatic visual inspection system(AVIS) has been modified to enable a user with little or no image processing background to define a system capable of identifying flaws on a given set of imagery. This system requires the user to simply identify flawed regions and the selection of processing and feature descriptors is performed automatically. This paper explicates the motivations, definitions, and performance issues associated with the AVIS paradigm.

Building and operating dependable systems is fundamental to many critical applications, such as designing integrated hardware and software systems for vehicles or satellites. Dependable systems techniques, methods, and tools are developed and used by researchers and practitioners working in widely varying disciplines. In order to provide a unifying framework for the successful dissemination and sharing of dependability results, the development of a dependable systems knowledge base is underway.1 Two database support subsystems are under development: one that manages the storage and retrieval of document information, as well as communicating between the user interface layer and the physical database layer, and another that manages the lexicon of dependability terminology for the user interface layer. The system will provide access to information in a sophisticated, intelligent manner that enables a human user to function more effectively in learning and decision-making capacities.

Acoustic array techniques are presented as alternatives to intensity measurements for source identification in automotive and industrial environments. With an understanding of the advantages and limitations described here for each of the available methods, a technique which is best suited to the application at hand may be selected. The basic theory of array procedures for Nearfield Acoustical Holography, temporal array techniques, and an Inverse Frequency Response Function technique is given. Implementation for various applications is discussed. Experimental evaluation is provided for tire noise identification.

In highly reverberant enclosures, the identification of noise sources is a difficult and time consuming task. One effective approach is the Inverse Frequency Response Function (IFRF) method. This technique uses the inverse of an acoustic FRF matrix, that when multiplied by operating pressure response data reveals the noise source locations. Under highly reverberant conditions the deployment of a sound absorbing body is especially useful in reducing the effects of resonant modes that obscure important information in the FRFs. Without the absorption, the IFRF method becomes practically difficult to perform in these environments due to poor conditioning of the FRF matrix. This study investigates the feasibility of using Boundary Element and Finite Element Methods to establish the frequency response functions between selected panel points and microphones in the array.

Practical issues to consider when making measurements for Nearfield Acoustical Holography (NAH) analysis are addressed. These include microphone spacing and placement from the test surface, number of microphones and array size, reference microphone number and placement, and filtering of the data. NAH has become an accepted analysis tool so that several commercial packages are available. Its application is limited to test surfaces that are fairly planar, lending itself well to tire testing, front of dash testing, engine face testing, etc. In order to achieve accurate NAH results, the measurement and analysis process must be clearly understood on a practical level. Understanding the advantages and limitations of NAH and the measurement parameters required of it will allow the user to determine if NAH is applicable to a particular test object and environment.

An enhanced, frequency domain filtered-x least mean square (LMS) algorithm is proposed as the basis for an active control system for treating powertrain noise. There are primarily three advantages of this approach: (i) saving of computing time especially for long controller’s filter length; (ii) more accurate estimation of the gradient due to the sample averaging of the whole data block; and (iii) capacity for rapid convergence when the adaptation parameter is correctly adjusted for each frequency bin. Unlike traditional active noise control techniques for suppressing response, the proposed frequency domain FXLMS algorithm is targeted at tuning vehicle interior response in order to achieve a desirable sound quality. The proposed control algorithm is studied numerically by applying the analysis to treat vehicle interior noise represented by either measured or predicted cavity acoustic transfer functions.

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