North Atlantic right whale localization and source level estimation using two coherently beamformed linear arrays.

Area of Science:

• Marine bioacoustics
• Oceanography
• Environmental acoustics

Background:

• Passive acoustic monitoring (PAM) is crucial for assessing marine mammal populations.
• Offshore wind development necessitates understanding potential impacts on marine life, particularly endangered species like the North Atlantic right whale.
• Accurate source level estimation is vital for interpreting acoustic data and assessing exposure risks.

Purpose of the Study:

• To estimate the mean source level of North Atlantic right whale upcalls.
• To evaluate the effectiveness of hydrophone arrays for localizing right whales in an offshore wind area.
• To characterize the acoustic environment relevant to marine mammal vocalizations.

Main Methods:

• Deployment of two bottom-mounted, 32-channel hydrophone line arrays for passive acoustic monitoring.
• Localization of North Atlantic right whales using cross-fixes from relative bearings to detected upcalls.
• Transmission loss (TL) testing to characterize the acoustic propagation environment (17 log(R)).

Main Results:

• Repeated detection and localization of North Atlantic right whales over a two-hour period.
• Estimation of the North Atlantic right whale upcall mean source level at 170 dB root-mean-square re 1 μPa @ 1 m (σ = 2.5 dB).
• Successful demonstration of hydrophone array capabilities for right whale detection and localization in the study area.

Conclusions:

• The estimated source level provides a critical baseline for right whale acoustic studies.
• Passive acoustic monitoring with beamformed hydrophone arrays is effective for detecting and localizing right whales in dynamic environments.
• Findings contribute to the responsible development of offshore wind farms by informing marine mammal monitoring strategies.