World’s lightest sound insulator could radically reduce jet engine noise

This graphene-based aerogel is the lightest sound insulation material ever manufactured, say researchers at the University of Bath, who have demonstrated its ability to damp down noise by up to 16 decibels despite weighing just 2.1 kg per cubic meter (0.13 lb per cubic foot).

You might not think weight is that much of a factor with acoustic foams, but to put this aerogel's density in context, compare it to a conventional polyester urethane sound absorber like Kinetics KUA, which was "developed to absorb maximum acoustical energy using minimum weight and thickness" with a density of 32 kg/m³ (2 lb/ft³). So in a given application, this new "graphene oxide-polyvinyl alcohol aerogel," squeezed into a Nomex honeycomb, would weigh less than one-fifteenth of an equivalent traditional acoustic foam installation.

Nowhere is weight so critical as in aerospace, and the Bath team has identified aircraft engine nacelle insulation as a key potential market for the technology, putting forth the example that it could potentially reduce the cabin noise of a jet airliner from the current 105-dB roar to something closer to a 95-dB hairdryer.

“This is clearly a very exciting material that could be applied in a number of ways – initially in aerospace but potentially in many other fields such as automotive and marine transport, as well as in building and construction," says Professor Michele Meo, who led the research. "We managed to produce such an extremely low density by using a liquid combination of graphene oxide and a polymer, which are formed with whipped air bubbles and freeze-casted. On a very basic level, the technique can be compared with whipping egg whites to create meringues – it’s solid but contains a lot of air, so there is no weight or efficiency penalty to achieve big improvements in comfort and noise.”

In their paper, the researchers say they believe the aerogel will have other useful properties, including fire resistance and electromagnetic shielding, and there's also the potential to develop it further to optimize its heat dissipation capabilities, which would be very handy in engine insulation. The team says it could be commercialized and in use within 18 months.

The research is open access in the journal Nature Scientific Reports.

Source: University of Bath