| 摘要 |
<p>In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones (2, 3, 4, 5) and two loudspeakers (6, 7) which form the active elements of a noise control system. The microphone outputs are fed via amplifiers (12, 13, 14, 15) to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller (10) and a synchrophased propeller (9), controlled by a synchrophaser (8). Thus the synchrophase angle is varied dynamically during flight to minimise propeller noise in the cabin over a range of flying condiditons.</p> |
