Loudness scattering due to vibro-acoustic model variability

Abstract

The use of numerical simulation in the design and evaluation of products performanceis ever increasing. To a greater extent, such estimates are needed in an early designstage, when physical prototypes are not available. When dealing with vibro-acousticmodels, known to be computationally expensive, a question remains, which is relatedto the accuracy of such models in view of the well-known variability inherent to themass manufacturing production techniques. In addition, both the academia and industryhave recently realized the importance of actually listening to a products sound, either bymeasurements or by virtual sound synthesis, in order to assess its performance. In thiswork, the scatter of significant parameter variations on a simplified vehicle vibro-acousticmodel is calculated on loudness metrics using Monte Carlo analysis. The mapping from thesystem parameters to sound quality metric is performed by a fully-coupled vibro-acousticfinite element model. Different loudness metrics are used, including overall sound pressurelevel expressed in dB and Specific Loudness in Sones. Sound quality equivalent sourcesare used to excite this model and the sound pressure level at the driver’s head position isacquired to be evaluated according to sound quality metrics. No significant variation hasbeen perceived when evaluating the system using regular sound pressure level expressedin dB and dB(A). This happens because of the third-octave filters that average the resultsunder some frequency bands. On the other hand, Zwicker Loudness presents importantvariations, arguably, due to the masking effects.Keywords: sound quality, vibro-acoustic model, finite element method, Monte Carloanalysis