The Volcano Acoustic Source: Decoupling Crater Modulation From Infrasound Signal

火山发出的强烈声音集中在次声带，低于人类听觉的频率阈值。这些声音通常在距离火山数公里处被记录下来，并被科学家和天文台用来持续观察喷发;通常次声被用来探测爆炸并测量喷发的强度和特征。这项研究的目的是提高对次声如何与火山口内发生的喷发过程有关的理解。为了实现次声作为一种有效的工具，有必要了解记录的声音信号是如何被火山口形状调制的。 这项工作的目的是测量，建模和量化火山口的声学响应的影响，这影响了辐射的声音很像一个乐器的号角。测量将包括现场工作，在活火山的火山口内外记录声场。预期结果将导致改进喷发过程的建模，并更好地认识火山动荡的变化。这项研究将汇集一个多元化的国际团队，不仅来自爱达荷州，而且来自夏威夷、智利、意大利和刚果民主共和国。这项工作还将资助研究生和本科生，并有助于令人兴奋的公共宣传机会，其中包括通过专业录像的组成部分记录的努力。火山口声学响应是一个传递函数，它将火山口底部发生的源过程与辐射到远处接收器的次声联系起来。了解火山口的声学响应是至关重要的，以提高效用的火山次声记录一般监测和改进物理为基础的喷发模型。在弹坑又深又窄和/或不对称的情况下，弹坑的声学响应可能特别极端，并可能显著扭曲源-时间函数。因此，火山口的声学响应的反褶积是恢复准确的源时间函数的关键。这项研究的综合数值模拟和实地工作，其中包括大N次声采样，将允许强大的量化火山口的声音调制效果。预期的结果将使研究人员能够更好地推断源参数，并反演火山口的几何形状，这可能会随着时间的推移在活火山动态变化。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Volcanoes radiate intense sounds concentrated in the infrasound band, which is below the frequency threshold of human hearing. Such sounds are often recorded many kilometers from a volcano and are used by scientists and observatories to continuously observe eruptions; commonly infrasound is used to detect explosions and to measure eruption intensity and character. This study's objective is to improve the understanding of how infrasound relates to eruptive processes occurring within a volcanic crater. To implement infrasound as an effective tool it is necessary to understand how the recorded sound signals are modulated by crater shape. This work aims to measure, model, and quantify the influence of the crater's acoustic response, which influences the radiated sound much like the horn of a musical instrument. Measurements will include field work where the sound field is recorded both within and outside the craters of active volcanoes. Anticipated results will lead to improved modeling of eruptive processes and to better recognition of changes in volcanic unrest. This study will bring together a diverse international team spanning numerical, analytical, and field expertise from not just Idaho, but Hawaii, Chile, Italy, and the Democratic Republic of the Congo. The work will also fund graduate and undergraduate students, and contribute to exciting public outreach opportunities which include chronicling the efforts through a component of professional videographies. The crater acoustic response is a transfer function, which relates source processes occurring at the bottom of a volcanic crater to the infrasound that is radiated to distant receivers. An understanding of the crater acoustic response is critical to improving utility of volcano infrasound recordings for both general monitoring and for improving physics-based eruption models. In cases where craters are deep and narrow and/or assymetric, the crater acoustic response can be particularly extreme and can significantly distort a source-time function. Deconvolution of the crater's acoustic response is thus critical to recovering accurate source-time functions. This study's integrated numerical modeling and field work, which incorporates large-N infrasound sampling, will permit robust quantification of the crater's sound modulation effects. Anticipated results will permit researchers to better infer source parameters and to invert for crater geometry, which may vary dynamically over time at active volcanoes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.