In 2012 a seismic survey campaign involving four vessels was conducted in Baffin Bay, West Greenland. Long-distance (150 km) pre-survey acoustic modeling was performed in accordance with regulatory requirements. Four acoustic recorders, three with hydrophones at 100, 200, and 400 m depths, measured ambient and anthropogenic sound during the survey. Additional recordings without the surveys were made from September 2013 to September 2014. The results show that (1) the soundscape of Baffin Bay is typical for open ocean environments and Melville Bay's soundscape is dominated by glacial ice noise; (2) there are distinct multipath arrivals of seismic pulses 40 km from the array; (3) seismic sound levels vary little as a function of depth; (4) high fidelity pre-survey acoustic propagation modeling produced reliable results; (5) the daily SEL did not exceed regulatory thresholds and were different using Southall, Bowles, Ellison, Finneran, Gentry, Greene, Kastak, Ketten, Miller, Nachtigall, Richardson, Thomas, and Tyack [(2007) Aquat. Mamm. 33, 411-521] or NOAA weightings [National Marine Fisheries Service (2016). NOAA Technical Memorandum NMFS-OPR-55, p. 178]; (6) fluctuations of SPL with range were better described by additive models than linear regression; and (7) the survey increased the 1-min SPL by 28 dB, with most of the energy below 100 Hz; energy in the 16 000 Hz octave band was 20 dB above the ambient background 6 km from the source.

Sound from seismic airgun pulses is well known to be a measurable component of the marine soundscape even hundreds of kilometers from the source vessel. The peak frequency of the pulses is normally below 100 Hz, and hence the concern is often raised that the airguns may mask the communications of large baleen whales. Recently, there have been reports of significant energy from seismic airguns in the range of 1–10 kHz which could mask calls from a wider range of marine life. Measurements and modeling of a variety of deep water environments are compared to show that environments with very hard bottom types support the long-range propagation of frequencies above 500 Hz from seismic airgun arrays.

It is a common practice for regulators to require project proponents to estimate the radius around a sound source where marine life could be injured or disturbed. Acoustic propagation modeling is normally required so that realistic radii are obtained that take into account the bathymetry, bottom properties, water column sound velocity profile, as well as source spectrum and directivity. Increasingly proponents are also asked to perform in-situ sound source characterization (SSC) measurements to verify the modeling predictions, including the spectrum and directivity of the sound source. During an SSC, sound levels are measured at increasing range from the source. In most cases, it is not possible to measure the sound levels at all ranges of interest, and therefore, the data must be interpolated or extrapolated to estimate the radii of the regulatory sound isopleths. This talk uses real-world data to identify the strengths and weaknesses of four methods of estimating the radii: (1) the practical spreading model; (2) linear interpolation; (3) linear regression with absorption; and (4) model-measured fits.

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In summer 2009, JASCO deployed ocean bottom hydrophones (OBHs) in the Chukchi Sea to measure natural and anthropogenic noise levels and monitor marine mammals acoustically. Acoustic data were collected from early August to mid October 2009. Ambient data were analyzed to compute noise levels for two sites: a relatively loud and relatively quiet one. Computer modeling was used to determine transmission losses at those sites. Manually acquired statistical data were used to determine average call length, and upper and lower frequencies for bowhead calls. Localization techniques were also used to determine source levels of the calls (Ref. Jonathan/Jeff paper). Using the above information and a modified version of the sonar equation, the space within which bowhead calls remain above ambient can be determined as an indication of maximum communication space. The noise conditions can be modified by simulating a ship passing through the area of an OBH and observing the change in communication space.