Graphene could reduce noise from aeroplanes
A new ultralight insulation material could be used in planes to reduce noise from the engines by up to 80%.
Millions of people who live close to airports are disturbed by the noise of flights overhead. But scientists from the UK’s University of Bath have invented a new sound insulation material that can reduce the noise from aircraft jet engines markedly.
Graphene-oxide polyvinyl alcohol aerogel (GPA) weighs only 2100g per m3, making it the lightest sound insulation material in the world. And the scientists have discovered that the material can reduce noise by 80% over normal materials in the frequency range of 4002500Hz. If it were used in the nacelle – the cylinder below the wing that includes the jet engine – aircraft noise might be reduced by about 16dB.
Since decibels are logarithmic units where -3dB represents a halving in perceived volume, this is a large drop. Reducing the sound pressure of a passing jet plane from some 105dB to only 90dB makes it about the level of a hair dryer. Such insulation on an engine would weigh only a few kilograms.
Graphene was first made in 2004. It is very strong and light, consisting of carbon atoms linked to each other in covalent bonds, by which the atoms share electrons with one another.
In the GPA insulation material, graphene oxide is mixed with polyvinyl alcohol – a material used for surface treatment of paper and plastic – giving it a meringue-like structure. GPA is currently more complicated and expensive to make than traditional insulation materials like mineral wool or fibreglass. But the aircraft industry could afford such prices to achieve significant benefits, if the weight is low.
At a later time, once costs are reduced, GPA could be equally useful in cars, shielding the interior from road noise, or in other structures where sound is to be kept in or out, such as anechoic chambers or home cinemas.
The scientists behind the invention of the new material hope that it will be commercially available within two years.