Presenter: Yuliya Kornikova (Reed College)

Description:
The Station ALOHA Cabled Observatory (ACO) is located in the Central North Pacific Ocean and is an ocean-bottom observatory that monitors ocean processes, including sound, continuously in real-time. Since sound propagates well underwater, the ACO hydrophone can study ocean acoustics over a broad scale. This allows for studying certain elusive marine mammals like baleen whales, who tend to stay in deeper water. The ocean-bottom hydrophone at the ACO can be used to track the occurrence of marine mammals, but can also record acoustic events such as glass balls shattering, ships passing by, and acoustic behavior of whales in a location that is difficult to study long-term due to its remoteness. We examined 12 months of 24kHz data from the ACO (January 2020- December 2020) and found a variety of sounds, some of which we identified as whale vocalizations. We created spectrograms of the audio files for visualization, analysis, and annotation. We analyzed and classified the sounds captured by the ACO hydrophone in order to be able to identify seasonal patterns and random occurrences and their causes. We identified sounds produced by minke, humpback, and sperm whales as well as a glass ball (used as flotation for a nearby mooring) popping. We found seasonality in humpback and minke whale sounds as they gradually leave in May and return in October. The ACO hydrophone has been in operation for a decade, and while we focus on the last 12 months in this study, the same methods could be used to show whether those patterns and occurrences change throughout the years. This work is meant to provide an overview of the types of sounds that the ACO is recording, and the identified signals can be used as training for machine learning for the development of a sound identification program that would be able to run in real time on the hydrophone.