Measuring the fluctuating static pressure within a jet has the potential to depict in-flow sources of the jet noise. In this work, the fluctuating static pressure of a subsonic axisymmetric jet was experimentally investigated using a 1/8” microphone with an aerodynamically shaped nose cone. The power spectra of the fluctuating pressure are found to follow the -7/3 scaling law at the jet centerline with the decay rate varying as the probe approaches the acoustic near field. Profiles of skewness and kurtosis reveal strong intermittency inside the jet shear layer. By applying a continuous wavelet transform (CWT), time-localized footprints of the acoustic sources were detected from the pressure fluctuations. To decompose the fluctuating pressure into the hydrodynamic component and its acoustic counterpart, two techniques based on the CWT are adopted. In the first method the hydrodynamic pressure is isolated by maximizing the correlation with the synchronously measured turbulent velocity, while the second method originates from the Gaussian nature of the acoustic pressure where the separation threshold is determined empirically. Similar results are obtained from both separation techniques, and each pressure component dominates a certain frequency band compared to the global spectrum. Furthermore, cross-spectra between the fluctuating pressure and the turbulent velocity were calculated, and spectral peaks appearing around Strouhal number of 0.4 are indicative of the footprint of the convecting coherent structures inside the jet mixing layer.

测量射流内波动的静压有可能描绘出射流噪声的流入源。在这项工作中，使用带有空气动力学形状鼻锥的1/8“麦克风，对亚音速轴对称喷头的波动静压力进行了实验研究。发现脉动压力的功率谱在射流中心线处遵循-7/3比例定律，并且衰减率随着探头接近声场而变化。偏斜和峰度的轮廓显示射流剪切层内部具有很强的间歇性。通过应用连续小波变换（CWT），从压力波动中检测出声源的时域足迹。为了将脉动压力分解为流体动力分量及其声学对应物，采用了两种基于CWT的技术。在第一种方法中，通过使与同步测量的湍流速度之间的相关性最大化来隔离流体动力压力，而第二种方法则来自于声压的高斯性质，其中凭经验确定分离阈值。从两种分离技术中都获得了相似的结果，并且与全局频谱相比，每个压力分量都在某个频带中占主导地位。此外，计算了脉动压力和湍流速度之间的互谱，并且出现在斯特劳哈尔数0.4附近的谱峰表明了射流混合层内部对流相干结构的足迹。而第二种方法则源于声压的高斯性质，其中凭经验确定分离阈值。从这两种分离技术中都获得了相似的结果，并且与全局频谱相比，每个压力分量都在某个频段上起着主导作用。此外，计算了脉动压力和湍流速度之间的互谱，并且出现在斯特劳哈尔数0.4附近的谱峰表明了射流混合层内部对流相干结构的足迹。而第二种方法则源于声压的高斯性质，其中凭经验确定分离阈值。从这两种分离技术中都获得了相似的结果，并且与全局频谱相比，每个压力分量都在某个频段上起着主导作用。此外，计算了脉动压力和湍流速度之间的互谱，并且出现在斯特劳哈尔数0.4附近的谱峰表明了射流混合层内部对流相干结构的足迹。