MULTIMEDIA ACOUSTIC PROPAGATION IN THE ARCTIC

Abstract

Understanding acoustic propagation within the Arctic environment is crucial to extending battlespace awareness and advancing strategic operations as the region becomes increasingly more accessible. This thesis expands upon prior work using broadband signals generated by lightbulb implosions deep in the water column to characterize acoustic signals as they propagate through three Arctic media—ocean, sea ice, and air—as well as their corresponding interfaces. Previous research has demonstrated that waterborne acoustic signals can couple to surface sea ice and transfer into the air, enabling inferences to be made about ice properties. For this research, impulsive lightbulb signals were recorded by means of hydrophones, cryophones, and microphones; signals were then examined through multiple techniques to calculate implosion depth and frequencies of interest. Using these data, the questions of optimal frequency for propagation, potential frequency shifts as a function of range, and behavior of the signal at depth were explored. It was determined that frequencies within the range of 0.13–3.0 kilohertz (kHz), with a dominant peak around 1.4 kHz, were most optimal for propagation through all three media. This research advances Arctic acoustic knowledge while identifying opportunities for further study and potential naval applications in autonomous monitoring via cryophones and microphones.