Design amp; analysis of acoustically improved vehicle floor carpets

摘要

The main objective of this research project is to design, develop and validate an innovative vehicle floor carpet system with improved acoustic performance, and thus reduce noise levels inside the vehicle cabins. The proposed solutions are expected to improve vehicle floor carpet product in areas of acoustic performance, cost, weight and waste reduction, to be environmentally friendly and sustainable in manufacturing. The following are main research outcomes of the project. • Acoustically improved vehicle floor carpet with higher sound transmission loss and in-cabin sound absorption coefficient, compared to current production carpet designs. • Vehicle floor carpet designs that introduce minimum weight and cost penalty for the acoustic performance improvement obtained. • Material database, i.e. measured acoustic parameters for mathematical modelling, of different vehicle carpet layers. • Virtual modelling and validation method for design evaluation at component and vehicle levels. • In-situ vehicle on-road validation test methods for carpet designs • Optimization methods for further improving the design The following are identified as recommendations for future design work in improving vehicle carpet acoustics. • Introducing air-gaps in the range of 10mm in between the heavy layers by use of a honey-comb structure improves the transmission loss by up to 20dB in the frequency range of 1kHz – 2kHz, and up to 10dB in the frequency range of 500Hz – 1kHz, and achieves the best sound transmission loss in these frequency ranges. • The introduction of honey-comb structure as an air-gap structure does not add any over-head in terms of weight or thickness, compared to foam, nor affects the total absorption of the carpet system. • Special tuned absorber layers like the perforated facing foam Helmholtz resonator and the corrugated foil faced foam membrane absorbers are excellent in extending the noise reduction frequency ranges to specific low frequency ranges of interest.