Multi-modal and short-range transmission loss in thin, ice-covered, near-shore Arctic waters

Abstract

In the past century, extensive research has been done regarding the sound propagation in Arctic ice sheets. The majority of this research has focused on low-frequency propagation over long distances. Due to changing climate conditions in these environments, experimentation is warranted to determine sound propagation characteristics in, through, and under first-year, thin ice sheets, in shallow water, over short distances. In April 2016 several experiments were conducted approximately 2 km off the coast of Barrow, Alaska on shore-fast, first-year ice, approximately 1 m thick. To determine the propagation characteristics of various sound sources, frequency response functions were measured between a source location and several receiver locations at various distances from 1 m to 1 km. The primary sources used for this experiment were, an underwater speaker with various tonal outputs, an instrumented impact hammer on the ice, and a propane cannon that produced an acoustic blast wave in air. The transmission loss (TL) characteristics of the multipath propagation (air, ice, water) are investigated and reported. Data indicate that TL in frequency bands between 125 and 2000 Hz varied from approximately 3-6 dB per doubling of distance which is consistent with geometrical spreading losses, cylindrical and spherical, respectively.

Limited vocal compensation for elevated ambient noise in bearded seals: implications for an industrializing Arctic Ocean

“…trills and plumes), and TL is the estimated transmission loss calculated as 15 × log(distance in m) [11,12,40]. This propagation loss model is simplistic-it accounts for geometric spreading loss only-but more complex transmission loss estimates made in this region in 2016 confirm that characteristics of multipath propagation made off the coast of Utquiagvik are consistent with geometric spreading loss used here [41]. Because the maximum frequency of bearded seal calls exceeds the upper frequency range of recordings, SL estimates for seals are band-limited (lowest frequency to highest identifiable frequency) and not inclusive of the entire vocal range.…”

Through-Ice Acoustic Source Tracking Using Vision Transformers with Ordinal Classification

“…In a deep water environment, such as the ocean, varying sound speed profiles present challenges in properly simulating the environment [1][2][3]. In ice environments, even more challenges arise: multi-path, scattering fields, interference patterns with a reflective ice surface, non-linear propagation through the ice, and a temporally changing field [4,5]. Additionally, shallow-depth, narrow, ice-covered waveguide environments (e.g., a frozen river or a canal) generate more multipath reflections on the bottom and edges of the environment.…”

Acoustic Localization Techniques for Application in Near-Shore Arctic Environments

“…To quantify the underwater transmission loss ( ) for the underwater tones, the meansquared pressure of each tone was determined at the source hydrophone, 2 ������� , and receiver hydrophone, 2 ������� , locations. For each tonal frequency, the source and receiver hydrophone data were time domain filtered with bandpass cutoffs at plus/minus 5% of the center frequency.…”

“…The ratio of autopower spectra between the receiver microphone and source microphone were then filtered into octave bands to determine the mean-squared pressure ratio in each respective band. The ratio of received meansquared pressure, 2 ���� , to source mean-squared pressure,…”

“…It should be noted that the difference in reference pressures between air and water was not accounted for. Only a ratio of mean-squared pressure at the receiver hydrophone, 2 ������� , to mean-squared pressure of the source microphone, 2 ���� , was computed. The TL in each frequency band was then converted to dB as shown in Equation 2.14.…”