A lot of time may have passed since your last flight because of the pandemic restrictions, but there’s probably one thing that you remember from then: the noise. Air travel is one of the fastest ways to travel long distances but also one of the noisiest ways to spend a couple of hours. Now, researchers have created a new material that could improve that experience substantially.

The noise from a plane is caused by air going over its body and from its engines. A moving aircraft causes friction and turbulence, which triggers sound waves — and the faster the aircraft is flying, the more turbulence and friction is produced. When the aircraft’s landing gear and flaps are used, more noise is made as more resistance is created.

Meanwhile, engine noise is caused by the sound of moving parts, and by the air coming out of the engine at high speed and interacting with still air, creating friction. Modern bypass engines, which introduce a layer of moderately fast-moving cold air between the hot exhaust and the still air, are quieter than early jet engines.

The elimination of aircraft noises may now be on the radar. A group of researchers at the University of Bath, UK, have developed a new material, inspired by the lightweight structure of a meringue dessert, that could significantly reduce aircraft engine noise and improve passenger comfort.

Silence!

The development of innovative acoustic materials has been of huge interest in the past decades, in particular, porous absorbers such as cellular foams have been extensively studied and adopted for several engineering applications. While they have good sound absorption, they are typically bulky and heavyweight, limiting their application.

That’s why the researchers at Bath started exploring the use of graphene oxide (GO), which they believe is an ideal candidate for engineering novel sound absorbers. The material has been evaluated in the past for various applications such as water treatment, energy storage and thermal insulation but never before for sound. 

Using graphene oxide, they created a low-density aerogel that weighs just 2.1 kilogram per cubic meter, making it the lightest sound insulation ever manufactured. Aircraft manufacturers could use it as insulation within aircraft engines to reduce noise by up to 16 decibels, reducing the road of a jet engine off to a sound similar to a hairdryer. 

“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,” Michele Meo, who led the research, said in a statement.

The material is currently being further developed by the research team to offer improved heat dissipation, offering benefits to fuel efficiency and safety. While their focus is to work with partners in aerospace to test the material in aeroplane engines, they believe it could also be used in helicopters or car engines. The aerogel should be ready to use in 18 months. 

The study was published in the journal Scientific Reports.