Abstract In this work, we experimentally study the acoustic response of water drop impacts onto a variety of surfaces using both audio recording and high-speed imaging. Audio recordings of the airborne sound emitted by single drop impacts on deep pools, thin liquid films, and dry aluminum and masonry surfaces are captured in the laboratory. Longer audio recordings are also collected for natural rainfall on wet concrete surfaces. These airborne sound pressure versus time measurements are converted to power spectra using the fast Fourier transform. Each impact type results in unique features in the spectra from 1 to 20 kHz that can be related to the impact and subsequent fluid phenomena. For example, in the case of water drops impacting a deep pool of water, we observe two distinct sound events: one as the drop breaks through the free surface of the pool with frequency content centered around 10 kHz and then approximately 50 ms later at the time of air cavity collapse and Worthington jet formation with frequency content around 4 kHz. A Helmholtz resonator model for the collapse of an air cavity describes the observed acoustic signature well. The acoustic spectra of various natural rainfall events on wet surfaces are comparable to those of discrete drops recorded in the laboratory, but upshifted in frequency.

中文翻译：

---

通过水滴撞击表面产生声音

摘要 在这项工作中，我们使用录音和高速成像实验研究了水滴撞击各种表面的声学响应。实验室记录了单滴撞击深水池、薄液膜以及干燥的铝和砖石表面时发出的空气传播声音的录音。还收集了较长的录音，用于潮湿混凝土表面的自然降雨。使用快速傅立叶变换将这些空气声压与时间测量值转换为功率谱。每种撞击类型都会在 1 到 20 kHz 的频谱中产生独特的特征，这些特征可能与撞击和随后的流体现象有关。例如，在水滴撞击深水池的情况下，我们观察到两个不同的声音事件：一种是当液滴突破水池的自由表面时，频率内容以 10 kHz 左右为中心，然后大约 50 毫秒后，在气腔坍塌和沃辛顿射流形成时，频率内容约为 4 kHz。用于空气腔坍塌的亥姆霍兹谐振器模型很好地描述了观察到的声学特征。潮湿表面上各种自然降雨事件的声谱与实验室中记录的离散液滴的声谱相当，但频率上移。