Long range propagation and refraction of acoustic signals measured on the Comprehensive Nuclear Test Ban Treaty hydroacoustic network in the Indian Ocean

Abstract

This paper investigates 3 days data collected on the Comprehensive Nuclear Test Ban Treaty hydro-acoustic network in the Indian Ocean. This data includes that from March 8, 2014, the day the Malaysian airliner MH370 went missing—presumably crashing into the Indian Ocean as evidenced by found aircraft debris. This presentation focuses on the earthquakes and other anthropogenic and natural sounds recorded at South Station of Diego Garcia [7.662 S, 72.613 E] and Cape Leeuwin located ~5,000 km away off of SW Australia [34.981 S, 114.144 E]. These measurements show that “hydroacoustic blockage,” shadowing caused by a land mass located between the source and the receiving station, is incomplete and that acoustic signals can be detected on the far side of an island. The land mass significantly alters the time and frequency dependence of the signal, in comparison to an unblocked path. Acoustic models are used to investigate this propagation phenomena, and suggest capability for localizing sound sources using “blocked” stations. The presentation also includes analysis of a conspicuous signal, localized to an area in the West Indian Ocean. The source of this signal is unknown, although it originated shortly after the last satellite last transmission from the missing airliner.