Development of an Arctic Low Frequency Ambient Noise Model

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Measurements of underwater ambient noise in the Arctic are of recent interest due to changes in the ice cover and increasing human activity. A series of noise measurements were conducted in the Marginal Ice Zone (MIZ) of the Fram Strait (Greenland Sea) in the years 2010-12. This presentation gives an overview of experiments conducted with fields of sonobuoys deployed by P-3 aircraft over 150 km x 150 km in the MIZ from open ocean to compact ice under varying environment conditions and in different seasons. Noise spectra at frequencies from 10 Hz to 1 kHz are presented and compared with historical data. The spectra are categorized by ice zones and discussed with respect to environmental parameters that include sea state, wind force and direction, ice concentration, ocean swell, and sound propagation conditions. Anthropogenic and biologic components of the noise fields including sound due seismic exploration activity and marine mammals are also discussed.

We present a new approach to characterize the background seismic noise across the continental United States. Using this approach, power spectral density (PSD) is estimated at broadband seismic stations for frequencies ranging from 0.01 to 16 Hz. We selected a large number of 1-hr waveform segments during a 3-yr period, from 2001 to 2003, from continuous data collected by the U.S. National Seismograph Network and the Advanced National Seismic System (ANSS). For each segment of continuous data, the PSD is estimated and smoothed in full-octave averages at 1/8 octave intervals. Powers for each 1/8 period interval were then accumulated in 1-dB power bins. A statistical analysis of power bins yields probability density functions (PDFs) as a function of noise power for each of the octave bands at each station and component. There is no need to account for earthquakes since they map into a background probability level. A comparison of day and night PDFs and an examination of artifacts related to station operation and episodic cultural noise allow us to estimate both the overall station quality and the level of earth noise at each site. Percentage points of the PDFs have been derived to form the basis for noise maps of the contiguous United States at body-wave frequencies. The results of our noise analysis are useful for characterizing the performance of existing broadband stations and for detecting operational problems and should be relevant to the future siting of ANSS backbone stations. The noise maps at body-wave frequencies should be useful for estimating the magnitude threshold for the ANSS backbone and regional networks or conversely for optimizing the distribution of regional network stations.

Scientific Reports

A longer Arctic open water season is expected to increase underwater noise levels due to anthropogenic activities such as shipping, seismic surveys, sonar, and construction. Many Arctic marine mammal species depend on sound for communication, navigation, and foraging, therefore quantifying underwater noise levels is critical for documenting change and providing input to management and legislation. Here we present long-term underwater sound recordings from 26 deployments around Greenland from 2011 to 2020. Ambient noise was analysed in third octave and decade bands and further investigated using generic detectors searching for tonal and transient sounds. Ambient noise levels partly overlap with previous Arctic observations, however we report much lower noise levels than previously documented, specifically for Melville Bay and the Greenland Sea. Consistent seasonal noise patterns occur in Melville Bay, Baffin Bay and Greenland Sea, with noise levels peaking in late summer and autumn c...

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Landscape Ecology, 2015

Noise Control Engineering Journal, 2011

This paper focuses on a re-analysis and updating of the 1974 report by the U.S. Environmental Protection Agency entitled: Population Distribution of the United Sates as a Function of Outdoor Noise Level, and commonly known as the 100-site survey. New data, about half of which were gathered throughout the country during 2008 and 2009 and about half of which were gathered in the Baltimore area in about 1998, are presented in this paper, where these different data sets are compared one to one another, and where the total combined data set in terms of the day-night sound level (abbreviated DNL and symbolized L dn) is examined as a function of population density. The main conclusions are that the original function in the EPA report yields results that are 3 dB higher than results obtained in a free-field situation, primarily because the measurements in that study used a microphone supported on a pole and at a distance of 1.8 m "6 ft… from the façade of the building. The new data confirm that the EPA predictions are 3 dB higher than those obtained for a free-field situation. A second main conclusion is that there is neither indication of any significant increase in overall ambient community noise exposure over the past 35 years, nor is there indication of any significant decrease in overall ambient community noise exposure despite 35 years of technological noise control improvements on transportation and other noise sources.

The Journal of the Acoustical Society of America, 2016

In March 2014, an Arctic Line Arrays System (ALAS) was deployed as part of an experiment in the Beaufort Sea (approximate location 72.323 N, 146.490 W). The water depth was greater than 3500 m. The background noise levels in the frequency range from 1 Hz to 25 kHz were measured. The goal was to have a threedimensional sparse array that would allow determination of the direction of sound sources out to hundreds of kilometers and both direction and range of sound sources out to 1-2 km from the center of the array. ALAS started recording data at 02:12 on March 10, 2014 (UTC). It recorded data nearly continuously at a sample rate of 50 kHz until 11:04 on March 24, 2014. Background noise spectral levels are presented for low and high floe-drift conditions. Tracking/characterization results for ice-cracking events (with signatures typically in the 10-2000-Hz band), including the initiation of an open lead within about 400 m of the array, and one seismic event (with a signature in the 1-40-Hz band) are presented. Results from simple modeling indicate that the signature of a lead formation may be a combination of both previously hypothesized physics and enhanced emissions near the ice plate critical frequency (where the flexural wave speed equals that of the water sound speed). For the seismic event, the T-wave arrival time results indicate that a significant amount of energy coupled to T-wave energy somewhere along the path between the earthquake and ALAS.

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Frontiers in Marine Science, 2017

Statoil deployed three acoustic recorders from fall 2013 to 2014 in the Arctic region as part of a broad scientific campaign. One recorder was installed in the Barentsz Sea southeast of Spitsbergen. Two other recorders were installed in the Greenland Sea northeast of Greenland. All recorders were operating at a duty cycle of 2 min on and 30 min off, sampling at 39,062 Hz and recording in 24 bits. The Greenland recorders both captured air gun surveys performed during the summer months of 2013, allowing to estimate the transmission loss in the Arctic over long ranges. This paper presents "log(R)" transmission loss curves for these scenarios that can help assessing the acoustic shipping impact for future expeditions.