民机噪声适航合格审定试验中地面影响研究

Effect of ground surface on civil aircraft airworthiness certification noise results

在民用飞机噪声适航合格审定试验中,传声器布置在地面上1.2 m处,测得的噪声包含地面影响。该文提出了一种分析地面对民机噪声适航合格审定试验中有效感觉噪声级影响的方法,并以ARJ21-700飞机噪声适航合格审定试验为例,对地面对飞越噪声的影响进行了计算和分析。在对飞行试验中飞机自由场声压级理论计算方法进行分析的基础上,通过飞越噪声测量点处布置的倒置传声器装置测量结果,计算了该测量点处的自由场声压级。随后,对满足"CCAR-36部"的不同地面声阻抗对噪声的影响进行了计算,分析了地面条件对噪声适航合格审定中有效感觉噪声级的影响。结果表明,地面声阻抗对噪声适航合格审定结果有明显影响,该方法可以为民用飞机噪声适航合格审定试验提供一种分析测量点地面的声学处理对噪声评定结果影响的手段。

Civil aircraft flight noise should be acquired by microphones mounted 1.2 meters above ground on airworthiness certification.Such a measurement method leads to misrepresentation of noise character due to ground surface interference effect.In order to analyze the effect on civil aircraft’s effective perceived noise level(EPNL),a method is presented and the interference effect on ARJ21-700 at flyover noise measuring point produced by ground surface is studied.On the basis of theoretical analysis method,through analyzing the data acquired by the inverted-microphone device,ARJ21-700’s free field sound pressure levels are obtained.Then the interference effect on EPNL of flyover produced by different finite acoustical impedance of ground surface which meets the certification requirements of CCAR-36 is analyzed.The results show that the acoustical impedance of ground surface has significant impact on noise results and the method presented could be used to evaluate the influence on EPNL of acoustic treatment of ground surface around measuring points on civil aircraft airworthiness certification.