Anthropogenic Noise in Cook Inlet Beluga Habitat: Sources Acoustic Characteristics and Frequency of Occurrence

A total of 13 anthropogenic sources of underwater noise were identified in a subsample of the acoustic recordings collected by the Cook Inlet Beluga Acoustics research program:

• commercial ship
• dredging
• helicopter
• jet aircraft (commercial or non-fighter)
• jet aircraft (military fighter)
• outboard engine (small skiffs, rafts)
• pile driving
• propeller aircraft
• sub-bottom profiler
• unclassified machinery (continuous mechanical sound; e.g., engine)
• unidentified 'clank' or 'bang' (impulsive mechanical sound; e.g., barge dumping)
• unidentified (unclassifiable anthropogenic sound)
• unknown up- or down-sweep (modulated tone of mechanical origin; e.g., hydraulics)

This subsample consisted of 8756 hours of the acoustic recordings collected in Cook Inlet, Alaska, from July 2008 to May 2013. The acoustic characteristics and frequency of occurrence of the noise were evaluated for potential for acoustic impact to Cook Inlet belugas. Several noise metrics were calculated (SLP in dB rms, SEL, dB 0-peak, power spectral density, 1/3 octave bands, and duration) and results were compared across noise sources, months, and locations. A total of 6263 anthropogenic acoustic events were detected and classified. These had a total duration of 1025 hours and represented 11.7% of the sound recordings analyzed.