Crackle is a perceptual feature of supersonic jet noise that is related to the presence of acoustic shocks. This study investigates the apparent source locations of the steepest shocklike events in the noise field of a high-performance military jet aircraft using an event-based time-domain beamforming method. This method uses the cross correlation between adjacent microphones to determine the angle of propagation of an ensemble of shock-related events within the time waveform. This angle of propagation is then traced back toward the source to find the apparent source location. Based on the propagation angle, derivative skewness, and overall sound pressure level, the microphone positions along the array are sorted into six groups. Shock events from groups related to crackle perception in the near field originate anywhere from 2 to 14.5 m downstream along the nozzle lip line, with distributions that shift downstream and broaden with increasing engine power. The crackle-related events appear to be generated by Mach wave radiation and large-scale turbulence structure noise.

裂纹是超音速喷射噪声的感知特征，与声震的存在有关。这项研究使用基于事件的时域波束成形方法研究了高性能军用飞机噪声场中最陡峭的类似冲击事件的表观源位置。该方法使用相邻麦克风之间的互相关来确定时间波形内与冲击有关的事件的集合的传播角度。然后将此传播角度追溯到源头，以找到表观源头位置。根据传播角度，导数偏斜度和总体声压级，沿着阵列的麦克风位置分为六组。来自与近距离爆裂感相关的群体的冲击事件起源于2到14。沿喷嘴唇线向下游5 m，随着发动机功率的增加，分布向下游移动并加宽。与裂纹相关的事件似乎是由马赫波辐射和大规模湍流结构噪声产生的。