Patent ID: 7533760

Claim:
A noise attenuation apparatus for ducts such as turbofan aircraft engines comprising: at least one tube having an inlet end and an outlet end, wherein the ends are separated by a distance capable of being varied during operation, wherein the ends are in fluid communication with the duct; at least one flexible tube branch attached in fluid communication to at least one end of the at least one tube; at least three ports wherein the at least three ports comprise: an inlet port at the inlet end of the at least one tube having an open position that allows the inlet end of the tube to be in fluid communication with the duct and a closed position to prevent the inlet end to be in fluid communication with the duct; a branch port that controls fluid communication between the at least one tube and the at least one branch tube; and an outlet port at the outlet end of the at least one tube having an open position that allows the inlet end of the tube to be in fluid communication with the duct and a closed position to prevent the inlet end to be in fluid communication with the duct.