Patent ID: 6360844
Filing Date: 2002-03-26
Classification: F02C,F02K,G10K,Y02T

Abstract:
A turbofan aircraft engine airflow duct having at least one acoustic liner material therein adapted for attenuating engine noise, wherein at least a portion of the liner is comprised of annular rings of at least two different materials, that are positioned in the airflow duct so that they alternate with respect to each other in the direction of the air flow, the materials including:(i) an absorptive material adapted to absorb high mode order noise, and (ii) and a multi-layer low-resistance acoustic material adapted to scatter low mode order noise and having a resistance coefficient in the range of from 0 to 0.5 &rgr;c, comprising a layer having a plurality of partitioned cavities, between an imperforate sheet and a perforate sheet, positioned in the airflow duct so that the perforate sheet is exposed to the air flow.