The Effect of an Acoustical Windscreen on the Sound Quality in a Car

P. D'Haene

This paper describes the effect of a new interlayer on the acoustical comfort in a car. Both computer simulations (at low frequencies) as well as experimental tests have been carried out to evaluate its effect. A modal analysis of the windscreen clearly shows an improved damping at the resonance frequencies to such an extent that at frequencies exceeding 200 Hz the modal behaviour is almost disappearing. This behaviour has also been evaluated once the windscreen was installed on a vehicle.

Besides the performance at low frequencies, also the influence of the new interlayer at high frequencies
has been investigated. This was carried out by means of transmission loss experiments using a reciprocal approach. Volume sound sources were installed in a car at different positions while the response at different microphones positioned along the vehicle was evaluated. The acoustical performance has also been evaluated in a dynamic test. During a motor run-up the vibrational damping as well as the sound pressure levels within the cabin have been measured. The data clearly indicate an improvement in articulation index (AI) of 5% or more when using the new interlayer, an effect which was hardly influenced by changes in temperature.

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