A study on the acoustic properties of light glass wool-melt blown limp fibre pad: Acoustic multilayer composite materials for automotive cockpit interiors

This study investigates a 2 mm light glass wool–melt blown limp fibre pad composite using an acoustic numerical model established in NOVA 2010. Based on the transfer matrix method (TMM), a single-factor numerical parameter sensitivity analysis was performed by independently varying the tortuosity, porosity and resistivity of the melt blown limp fibre pad layer to investigate their effects on transmission loss, normal-incidence sound absorption coefficient, complex reflection coefficient, and complex surface impedance. The results show that, for the present 2 mm composite, individual variations in tortuosity, porosity, and resistivity have an overall limited influence on the acoustic response in the low- and mid-frequency regions of the investigated range, whereas the sensitivity of different acoustic response quantities to these parameters becomes more apparent with increasing frequency. The analysis was further extended using the finite transfer matrix method (FTMM), and a double-wall structure model under diffuse field excitation was established to investigate the effects of wall-panel configuration and Inner cavity widths of 10–30 mm on transmission loss. In addition, ± 5% wall-panel thickness perturbations were introduced to evaluate the local structural robustness of the numerical predictions for three different double-wall configurations. The results indicate that wall-panel configuration has a pronounced influence on transmission loss. The Aluminium & Honeycomb Sandwich configuration provides relatively high predicted transmission loss while offering greater potential for lightweight applications. In the 10–30 mm range that was studied, the Inner cavity width has a non-monotonic effect on low-frequency transmission loss. However, above 500 Hz, the differences in transmission loss between the different Inner cavity widths become much smaller. The ±5% wall-panel thickness perturbation analysis also shows that the Thick Steel Plate Property configuration is more sensitive to changes in thickness in certain areas. This study provides a numerical reference for parameter selection and structural design of lightweight acoustic materials for automotive applications.