The underwater soundscape was recorded in Seaview Bay off Inexpressible
Island, Ross Sea region Marine protected area, for three days in
December 2021. Leopard seal Hydrurga leptonyx vocalizations were a
prominent sound source that led to variations in ambient sound pressure
levels in a frequency range of approximately 150 to 4,500 Hz. Among the
14 call types previously identified, except ultrasound vocalizations,
six types of broadcast calls were classified, and their acoustic
characteristics were analyzed. We focused on the acoustic
characteristics of four low-frequency calls, clustered in a relatively
narrow bandwidth, which have been relatively less studied. We identified
a new call type of a triple ascending trill consisting of three trill
parts, expanding upon the findings of previous studies. The audio data
extracted from leopard seal vocalization videos, recorded by a
monitoring camera on sea ice, enhanced the reliability of
identifications of the underwater triple ascending trill. We present the
unique results of underwater passive acoustic monitoring conducted at
Seaview Bay, designated as Antarctic Specially Protected Area No 178.
Our results could contribute to the development of detection and
localization algorithms for leopard seal vocalizations and can be used
as fundamental data for studies related to the vocalization and behavior
of this species.