In 2020, Eastman launched a new acoustic PVB interlayer for automotive laminated glass. This interlayer not only helps to protect driver and passengers from injuries during impact but also provides enhanced acoustic comfort in the car. This newly developed interlayer offers substantially improved acoustic performance in the high-frequency range that is typically associated with wind noise at higher vehicle speeds. To demonstrate the in-vehicle performance, finite element simulations have been carried out using wind noise as the principal source of excitation. The results confirm previously published data that the acoustic contribution overwhelms the turbulent part, having a larger contribution to the ultimate acoustical pressure level.
The acoustic insulation calculated is in excellent agreement with the static sound transmission loss data as measured according to the ISO or ASTM norm. In cases where both the windscreen and front-side windows have a laminated structure, a large improvement in sound level is achieved by the acoustic interlayers, mainly in the 3,000 to 6,000 Hz frequency range. With the newly developed Saflex® E series interlayer, a further improvement in the higher frequency range is realized. In this simulation exercise, the relative contribution on the sound pressure level of laminated front-side windows in comparison with tempered glass has also been analyzed.
Besides, qualitatively similar results are obtained from an experimental simulation of rainfall at various intensities and angles of impact. With acoustic interlayers, a general reduction in sound level is measured, with an additional gain in the high-frequency range for the new E-series product. This behavior mirrors the performance level observed from the static sound transmission loss experiments.