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The advancement of numerical methods for acoustics has enhanced the ability to make meaningful predictions of acoustic responses in vehicle passenger compartments, such as those found in automobiles, trucks, and construction equipment. A design objective of growing importance is to isolate the occupants from both structural and air-borne noise. This paper presents how an indirect boundary element formulation can be used to study the effect of holes on the transmission of air-borne sound, and how design changes effect the transmission of sound through heater and air conditioning ducts. The theoretical background of the indirect formulation is also presented. The significance of this method is that it can include openings in the model while considering the acoustic medium on both sides of the mesh. It is also computationally superior to the direct method because the assembled matrices are symmetric.

TORVIB is a general purpose program which provides a quick, complete torsional analysis of the many unique drivelines specified by truck customers. This program has been recently modified to include universal joint effects. In the updated program, finite element methods are used to calculate maximum vibration angles, maximum vibration torques, and secondary couples caused by dynamic engine torques and universal joints. The techniques of modeling universal joint effects which are described in this paper can also be used to analyze drivelines with commercial finite element software. Universal joint effects were added by first updating the mass and stiffness matrices to include degrees of freedom at each yoke on a universal joint. Rotational constraint equations were then written for each universal joint and applied using the large stiffness method. Finally, post-processing calculations were added to recover the secondary couples at each yoke.

A computer program has been developed chat will analyze torsional vibration in heavy and medium duty trucks. The capabilities designed into this program provide for a quick, complete torsional analysis of the many unique drivetrains specified by truck customers. The program utilizes a database for storage of drivetrain component mass/elastic data and engine force data. Also, modern matrix methods are used to calculate natural frequencies, mode shapes, and forced response characteristics of a drive-train.