Methods for Aircraft Noise and Vibration Analysis

Sammanfattning: Aircraft noise control engineering is a challange both for experimentally based methods and for numerical analysis methods. Usually noise control installations are designed based on engineering judgement in combination with results from in-flight testing, rather than with nummerical methods, due to the absence of reliable and accurate models.For turbo-prop aircraft, such as the Saab 340 and Saab 2000, the low-frequency tonal noise generated by the propellers is a major reason for passenger discomfort. Two effective methods of reducing this propeller noise are tuned vibration absorbers/dampers and active noise control. The efficiency of both of these two methods is, to a great extent, determined by placement of the damper/absorber or active actuator (structural exciter or loudspeaker). Finding appropriate locations for such installations from experiments requires extensive testing, both in-flight and on ground. If alternative design methods requiring less, or ideally no, testing could be utilized this would allow significant cost reduction and the possibility of concurrent design for the noise control installations.That is the motivation for this study on methods for aircraft acoustic and structural vibration analysis.