Noise absorption system having active acoustic liner
AssigneeNorthrop Grumman Corporation
InventorsWilliam C. Van Nostrand, Charles A. Parente, Noe Arcas
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Abstract
The present invention is embodied in an aircraft engine noise absorption system having a resonator cavity for absorbing incident noise except for a residue noise signal having a predominant frequency, the system comprising an actuator providing an actuator acoustic signal, a noise sensor for sensing the predominant frequency, and a controller for setting the actuator acoustic signal to the predominant frequency and varying one of a phase and an amplitude of the actuator acoustic signal to decrease the residue noise signal.
Claims26
An aircraft engine noise absorption system having a resonator cavity for absorbing incident noise except for a residue noise signal having a predominant frequency, said system comprising:
- an actuator providing an actuator acoustic signal;
- a microphone mounted in said cavity for sensing said predominant frequency;
- and
- a controller for setting said actuator acoustic signal to said predominant frequency and varying one of a phase and an amplitude of said actuator acoustic signal to decrease said residue noise signal.
A noise absorption system for reducing aircraft engine noise, comprising:
- a sound absorbing resonator cavity;
- a sound wave generating actuator acoustically coupled to said cavity providing a secondary noise signal;
- a microphone mounted in said cavity and acoustically coupled to said cavity;
- and
- a controller responsive to unabsorbed reflected noise sensed by said noise sensor for setting a frequency of said secondary noise signal approximately the same as an incident noise signal and varying at least one of an amplitude and a phase of the secondary signal to increase absorption of the incident noise signal by said cavity.
A noise absorption system for use with a passive acoustic liner composed of a plurality of contiguous honeycomb cells, said system comprising:
- a sound wave generating actuator acoustically coupled to one of said cells;
- a microphone mounted in said cavity and acoustically coupled to said cell;
- and
- a controller coupled to said noise sensor and for providing an actuator control signal having a frequency approximately the same as an incident noise signal and varying at least one of an amplitude and a phase of the control signal to increase absorption of the incident noise signal by said cell.
A method of absorbing aircraft engine noise comprising the steps of:
- acoustically coupling a sound wave generating actuator to a sound absorbing resonator cavity;
- mounting a microphone in said cavity and acoustically coupling said microphone to the cavity to produce an output signal responsive to an incident noise signal;
- analyzing the sensor output signal to determine a frequency and at least one of an amplitude and a phase of the incident noise signal;
- generating a noise absorbing signal coupled to the actuator having a frequency approximately the same as the incident noise signal and varying at least one of an amplitude and a phase of the noise absorbing signal to increase absorption of the incident noise signal by said cavity.
Dependencies are inferred from the claim text.