A survey of signals and noise at high-frequency infrasound arrays in Nevada and South Korea

The development of the International Monitoring System infrasound network, combined with additional deployments of regional infrasound arrays, has led to enhancements in our understanding of acoustic signals and noise in the 0.1–5 Hz range over the last two decades. The goal of this study is to explore the properties of signals and noise at higher frequencies: from high-frequency (HF) infrasound to low-frequency (LF) audible (1–30 Hz). By embedding two new HF infrasound arrays within existing regional arrays in Nevada and South Korea, we are exploring the signals observed at these frequencies and assessing how such HF arrays can complement traditional regional infrasound arrays. In addition to observing regional infrasound signals that vary seasonally due to the stratospheric winds, repeating local sources are identified at each array, including mining explosions and operational signals such as machinery. Notable detections from the OSIRIS-REx reentry, missile and satellite launches, and the 2024 MW 7.5 Noto earthquake are highlighted. In addition to cataloging signals, we extend noise models to the HF infrasound/LF audio range, assessing coherent and incoherent noise contributions. We find that the new HF arrays extend the capability of traditional regional arrays by detecting new local signals and providing new information on regional signals, and they open the understanding to study HF infrasound propagation at local distances.