Sponge-like material fights jet noise

A sponge-like material that can reduce the noise of combustion could make work environments safer and extend the life of equipment, U.S. researchers say. This technology lessens the noise generated by combustion systems such as those in a jet engine at the source by placing a sponge-like material directly in the flame, University of Alabama mechanical engineer Ajay K. Agrawal, who has patented the material, said. The combustion process in jet engines produces a deafening noise that can also be devastating to the engine, as sound waves can shake the engine and result in mechanical failure, a university release said Tuesday. This porous inert material, a foam made of hafnium carbide and silicon carbide, which can withstand intense levels of heat and pressure, is placed directly into the flame and acts like a sponge for the noise, Agrawal said. The foam allows gases to easily flow so combustion is not interrupted, yet is much quieter. It surrounds the flame, cuts the noise and eliminates the potential for engine instability, he said. "Experimenting with combustion can be quite noisy and unstable, shaking the whole building, but when you put the foam in place, you can talk to the person next to you. It's a night and day difference," Agrawal said. The foam reduces noise at its source, minimizing the need for bulky and expensive modifications to exhaust equipment, he said.