Punekar J N, Avital E, Li X
School of Materials and Engineering, Queen Mary University of London, Mile End, London, E1 4NS, United Kingdom.
School of Energy and Power Engineering, Beihang University, Xueyuan Road 37, Beijing, 100191, China
J Acoust Soc Am. 2017 Jun;141(6):EL567. doi: 10.1121/1.4985585.
Supersonic crackle, an irritable component of aircraft jet noise, was investigated using model scale measurements. Near-field results showed Gaussian distribution but far-field had high skewness and even higher in its derivative. Skewness, a measure of asymmetry in the waveform, was compared to screech arising from shock associated noise which was also high but in contrast to crackle its skewness derivative had dropped to a much smaller value than its waveform. Both crackle and screech are nonlinear but their nonlinear properties are entirely different. Crackle is quantified when its derivative skewness becomes larger than its waveform skewness which should exceed 0.3.
超声爆音是飞机喷气噪声的一个恼人成分，利用模型尺度测量对其进行了研究。近场结果呈现高斯分布，但远场具有高度偏度，其导数更高。偏度是波形不对称性的一种度量，将其与由激波相关噪声产生的啸声进行了比较，啸声的偏度也很高，但与爆音不同的是，其偏度导数已降至比其波形小得多的值。爆音和啸声都是非线性的，但它们的非线性特性完全不同。当爆音的导数偏度大于其波形偏度（应超过0.3）时，爆音就被量化了。
