ARCTIC UNDERWATER ACOUSTICS

Year Published: 1965

Description:

This film "Arctic Underwater Acoustics" (1965) looks at a series of experiments conducted in the northern arctic using the DIMUS hydrophone system. DIMUS was used for research purposes to analyze underwater signals in the cold, iceberg infested waters, with the hope of being able to detect Soviet submarines operating at the top of the world.
In 1958, the submarine USS Nautilus proved the Arctic Ocean could be used for nuclear submarine operations, though it posed unique challenges. To better understand underwater sound in the Arctic, which is crucial for submarine warfare, a research team set up a permanent station on Ice Island T-3, aka Fletcher's Ice Island, located 450 miles north of Barrow, Alaska. The station hosted the DIMUS processor system, a network of hydrophone holes and seismometers designed for underwater signal analysis. The team also conducted experiments by linking T-3 with a temporary station, Arlus 4, 100 miles away, using underwater explosions to generate low-frequency signals. These signals, along with ambient sounds like ice creaks and marine animal calls, were analyzed to improve knowledge of Arctic underwater acoustics. The project was completed by the GM Defense Research Laboratory's 1965 expedition, marking the successful installation of the system for the year. (Note: Fletcher's Ice Island or T-3 was an iceberg discovered by U.S. Air Force Colonel Joseph O. Fletcher. Between 1952 and 1978 it was used as a staffed scientific drift station that included huts, a power plant, and a runway for wheeled aircraft.) (Note: DIMUS [Digital Multi-beam Steering] is a technology that enhances the capabilities of hydrophone arrays, allowing for omnidirectional sound detection and tracking in three dimensions, crucial for passive sonar systems on submarines. )

0:00 In 1958, the submarine USS Nautilus crossed the Arctic Ocean submerged, proving the area was usable for nuclear submarines, but with unique challenges.

0:29 - The need for more knowledge about underwater sound in the Arctic, critical for submarine and anti-submarine warfare, is introduced.

0:49 - The research team set up their station on Ice Island T3, located 450 miles north of Barrow, Alaska. Unlike pack ice, Ice Island is stable and ideal for permanent installations.

1:28 - The setup of the Deeus project system on Ice Island T3 is described, including a network of hydrophone holes and seismometers placed in the ice, with cables connecting to a central array.

1:58 - Aerial view of the permanent installation shows the system’s ability to form preformed beams over 360° for underwater signal analysis.

2:21 - The DIMUS processor allows for varied averaging times and frequency discrimination to analyze underwater sounds.

2:23 - A second team was sent to Arctic Research Laboratory Ice Station IV (known as ARLIS IV), a temporary station 100 miles from Barrow, to link the two stations by radio telephone for signal experiments.

2:40 - The team at T-3 receives calls and arranges for sound signal tests. The experiment involves sending signals to a hydrophone at a distance.

2:47 - The sounds used in experiments are generated by Mark 61 underwater sound sources, detonated under the ice at specific intervals.

3:07 - Explosions from TNT bombs detonated under the ice are captured by electronics at Arlus 4, with only low-frequency sounds being received due to scattering by the ice.

3:21 - Other ambient sounds, like the creaking and popping of ice, and voices of seals and whales, are also captured and analyzed.

3:41 - With the Deeus system established at T-3 and ARLIS IV's work complete, the GM Defense Research Laboratory's 1965 expedition finished its installation tasks for the year. (Note: ARLIS IV operated between February and May of 1965.)