| 摘要 |
<p>An aircraft configuration that may reduce the level of roaring jet exhaust noise, infrared radiation, sonic boom, or combination thereof directed towards the ground from an aircraft in flight. The aircraft's nacelles (78,80) are mounted to the aircraft higher than the wings (102,104), with substantially vertical stabilizers (82,84) outboard of the outermost engine. Noise shifting means are provided such as, for each nacelle, primary chevrons (220) at the core nozzle, secondary chevrons (222) at the fan nozzle, a partial bypass mixer (242), a long duct full flow mixer, or a combination thereof to provide a shift in spectrum distribution of jet exhaust noise from lower to higher frequency. Variable geometry chevrons may be used with increased immersion to provide such a shift just during noise-restricted portions of an aircraft flight profile. The aircraft aerodynamic structural surfaces serve as noise shielding barriers that more effectively block or redirect the frequency shifted noise up and away from communities.</p> |
