Dual-perspective high-speed imaging and acoustic detection is used to characterise cavitation activity at the tip of a commercial 20 kHz (f₀) ultrasonic horn, over 2 s sonications across the range of input powers available (20 – 100%). Imaging at 1 × 10⁵ frames per second (fps) captures cavitation-bubble cluster oscillation at the horn-tip for the duration of the sonication. Shadowgraphic imaging at 2 Mfps, from an orthogonal perspective, probes cluster collapse and shock wave generation at higher temporal resolution, facilitating direct correlation of features within the acoustic emission data generated by the bubble activity. f₀/m subharmonic collapses of the primary cavitation cluster directly beneath the tip, with m increasing through integer values at increasing input powers, are studied. Shock waves generated by periodic primary cluster collapses dominate the non-linear emissions of the cavitation noise spectra. Transitional input powers for which the value of m is indistinct, are identified. Overall shock wave content within the emission signals collected during sonications at transitional input powers are reduced, relative to input powers with distinct m. The findings are relevant for the optimisation of applications such as sonochemistry, known to be mediated by bubble collapse phenomena.

双视角高速成像和声学检测用于表征商用20 kHz（f ₀）超声变幅杆尖端的空化活动，在可用输入功率范围（20 – 100％）范围内进行2秒钟的超声处理。以每秒1×10 ⁵帧（fps）的速度成像，可以在声波作用期间捕获角尖处的气蚀气泡簇振荡。从正交角度看，以2 Mfps的速度成像成像可在更高的时间分辨率下探测团簇坍塌和冲击波的产生，从而促进了气泡活动所产生的声发射数据中特征的直接相关性。f ₀ / m在尖端正下方的主要气蚀团的次谐波崩溃，研究了在输入功率增加时通过整数值增加的m。周期性一次簇破裂产生的冲击波主导了空化噪声频谱的非线性发射。标识m值不明显的过渡输入功率。相对于具有不同m的输入功率，在过渡输入功率下超声处理期间收集的发射信号中的总冲击波含量降低了。这些发现与优化应用有关，例如声化学，是由气泡破裂现象介导的。