Interior Acoustic Simulation for In-Car Audio Design

Today’s automotive audio components have to meet high quality expectations with ever-decreasing development costs. Predictive methods for the performance of sound systems in view of the optimal locations of loudspeakers in a car can help to overcome this challenge. This article describes a number of sound-field simulation tools to model the acoustic and vibro acoustic aspects that come into play when transducers are mounted into small areas such as passenger compartment and door cavities. Examples are shown how FEM software can predict the acoustic modes of
passenger compartments and door cavities. Automatic volume meshers are key to the success of the Acoustic FEM solutions. Vibro acoustic effects, such as speaker membrane vibrations coupled with door cavity acoustic pressures and vibrations on the door trim can be taken into account using coupled structural and acoustic FEM and BEM formulations. Also fast-multipole BEM is used to boost the realistic frequency range up to 5000 Hz and higher. For very-high frequency modeling (above 5000 Hz), beam-tracing algorithms based on principles of ray acoustics can be deployed to synthesize binaural impulse responses and deriv-ing IACC-index maps. Aspects of absorbent material properties (complex acoustic impedance) and speaker characterization (velocities) are discussed.

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