Non-lethal device deters hostile divers
Hostile divers may be deterred from approaching U.S. Navy ships, sea ports, off-shore oil rigs, and other infrastructure facilities with an acoustic device that overwhelms them with the amplified sound of their own breath; the device generates low frequency underwater sound that interferes with breathing, induces disorientation, panic, uncontrolled ascent to surface, and decompression sickness
A researcher in the United States is developing a non-lethal weapon for protecting ports from divers with malicious intentions.
Dr. Alexander Sutin, a research professor at Stevens Institute of Technology, New Jersey, believes such divers could be thwarted with an acoustic device that overwhelms them with the amplified sound of their own breath.
The technique may offer DHS and the U.S. Navy an alternative to underwater explosive charges or loud underwater sirens, which may negatively impact marine life.
According to a paper by Sutin and Dr. Yegor Sinelnikov, current underwater sound systems to deter divers generate low frequency underwater sound that interferes with breathing, induces disorientation, panic, uncontrolled ascent to surface, and decompression sickness. Strong sound with acoustic pressure above 170-180dB can cause lung and liver damage.
Marine life and other divers can suffer, too, because the sound is radiated in all directions.
The Engineer reports that Sutin’s idea is to detect the diver’s breathing passively instead of using an active acoustic technology such as a sonar ping. The acoustic noise given off by the diver could be used to focus acoustic energy back to the diver because he or she acts as an active self-disclosing acoustic beacon.
Time Reversal Acoustics (TRA) has been proposed to produce a precise, amplified beam of sound loud enough to overwhelm an intruder.
The major advantage of proposed approach is that the TRA system for non-lethal neutralization focuses all radiated, refracted, reflected and scattered underwater sound back to a hostile swimmer.
The next step in the development of the technology will be to create a method to isolate a narrow band of the breathing sound and radiate it back to the diver.
—Read more in Alexander Sutin and Yegor Sinelnikov, “Time Reversal Acoustic Approach for Non-Lethal Swimmer Deterrent” (paper presented at the 2nd Pan-American/Iberian Meeting on Acoustics, Cancun, Mexico, 16 November 2010)
