초록 ▼

An array of adaptive or fixed Herschel-Quincke tubes aligned in a circumferential or helical array about an inlet of a turbofan engine. The array of tubes effectively divide the acoustic energy generated by the engine. One of the energy components propagates within the tubes while the other propagat

An array of adaptive or fixed Herschel-Quincke tubes aligned in a circumferential or helical array about an inlet of a turbofan engine. The array of tubes effectively divide the acoustic energy generated by the engine. One of the energy components propagates within the tubes while the other propagates within the engine compartment. At some time certain, the acoustic energy in the tubes is reintroduced into the engine compartment to cancel the acoustic energy remaining in the engine as it propagates from the fan towards the inlet and outlet openings.

대표청구항 ▼

[ We claim:] [1.] A noise reduction system comprising:means for generating non-uniform noise energy about an inner surface and within an enclosure having at least an inlet;at least one array of tubes each having an inlet and an outlet, the inlet and the outlet of each tube of the at least one array

[ We claim:] [1.] A noise reduction system comprising:means for generating non-uniform noise energy about an inner surface and within an enclosure having at least an inlet;at least one array of tubes each having an inlet and an outlet, the inlet and the outlet of each tube of the at least one array of tubes communicating with apertures in the enclosure and the at least one array of tubes being positioned about an outer surface of the enclosure, portions of the enclosure having an effective length L.sub.2 between the inlet and the outlet of each of the tubes and the tubes having a length L.sub.1, where L.sub.1 >L.sub.2,wherein said non-uniform noise energy divides into two components at the inlet of each of the tubes of the at least one array of tubes, a first component of the non-uniform noise energy propagates through each of the tubes over the length L.sub.1 and a second component of the non-uniform noise energy propagates through the enclosure over the effective length L.sub.2 such that when the non-uniform noise energy exits the outlet of each of the tubes, the non-uniform noise energy is out-of-phase and recombines with the non-uniform noise energy propagating over the effective length L.sub.2 thus reducing the noise levels generated from the means for generating noise energy.