Design, manufacturing and demonstration of acoustic liners for air conditioning systems

Until now, acoustic liners for air conditioning systems are made of porous materials, very efficient for sound absorption in the high-frequency range. However, Liebherr Aerospace is developing an electrically driven air system composed of an air pump which generates low-and mid-frequency noise. New kinds of acoustic liners are therefore required to mitigate this noise source. The ALIAS project (Acoustic Liners for Air conditioning Systems) has been launched in the framework of Clean Sky Systems for Green Operations platform for addressing this issue. The project aimed at designing optimized locally reacting treatments for mid-frequency acoustic attenuation in air conditioning systems. SDOF and DDOF liners , which are standard solutions for acoustic treatments in turbofan engines, were adapted to the air conditioning system environment. The French Aerospace Lab (ONERA) and the SME ATECA, specialized in Advanced Materials & Systems, combined their research and technological capabilities to propose solutions that meet the industrial requirements. This was achieved by implementing a simulation-based design process, performing dedicated laboratory experiments, manufacturing full scale prototypes and demonstrating their efficiency in the anechoic facility of Liebherr Aerospace.