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During acceleration, engine combustion is the major sound source in passenger vehicles.[1] This sound characterizes the overall impression made by the vehicle. Automobile manufactures have been developing engines to have better sound characteristics since the late 1980s.[2] However, fundamental and systematic knowledge of the relationship between the basic structural dynamics of the engine and its sound characteristics has not yet been reported. In addition, in the design stage, engine designers were not previously able to listen to the sound generated by the engines. This paper introduces a tool that synthesizes engine combustion sound by specifying the combustion process and a basic engine structural dynamics model having a small number of parameters. Using this tool, the authors obtained important relationships between combustion process and subjective sound characteristics evaluation scores.

A formula type racing-car was designed and built for the “Formula SAE” competition. Lightweight design was achieved separately in two areas, i.e. the pipe frames and bulkheads, by employing two different strategies. In the pipe frame design, the stretch method was used. The baseline design employed the minimum number of pipes required to make the structure statically stable. After this, reinforcements were attached one-by-one, until the rigidity reached a satisfactory level. In the bulkhead design, weight reduction was achieved using a voxel approach and topology optimization. The bulkhead was divided into finite elements that have the same shape and size. Starting from a solid board, relatively low-stress parts were removed from the model in a step-by-step manner. The weight of the final design is less than 50% of that of the solid board.

One potential method by which to realize better acoustic in-car entertainment with a minimum of space is to adopt very thin Flat-Panel Speakers (FPSs), which use a combination of an array of coils printed on a flexible thin plastic film and permanent magnets. In the present report, the optimal panel material was investigated through experimental modal analysis. The optimal driving unit placement over the board was then determined using FEM based modal analyses. Finally, structural modifications to the sound radiating board in order to obtain a wider efficient frequency range were investigated experimentally. Among several design alternatives, satisfactory results were obtained by either dividing the sound radiating board into virtually independent sub-panels or adding resilient damping material supported by a restraining material.