Low power sonar helps dolphins and battery life

Advances in signal and data processing have allowed the development of an underwater acoustic link that is so low powered that, according to SonarLink’s chief technical officer Dr Hong Kwang Yeo, the signals are almost hidden behind environmental noise. He added these levels are ‘500 to 800 times lower than current technology’. This is not only good for operators, reducing time to collect data by two thirds, it’s also good for dolphins and whales. Dr Yeo said: “At present, significant undersea acoustic data transmission makes a noise equivalent to that of a jet engine, which is disturbing to dolphins and other sea life. This noise can go on for days at a time while data is transmitted from collectors to the base station. Our system reduces the noise dramatically, say to the level of a quiet car engine, and can reduce the duration of the noise by up to two thirds”. The technology includes a method of compressing information in such a way that data from several devices can be received at the same time. According to Dr Yeo, this is ‘beyond multiplexing’ and currently allows data to be transmitted at 8.4kbit/s. He believes higher data rates are possible. “Sea-bed crawlers, remote controlled vehicles and sub-sea units all collect information about their surroundings,” explained Dr Yeo. “This is sent via an acoustic signal to a base station, which is usually connected to a ship or oil platform. But each of the data collectors has to transmit in turn because, until now, the base station could not understand the signals if they were sent simultaneously. We have solved this problem so all sub-sea units can ‘talk’ to the base station at the same time. This can reduce the time taken for data transmission significantly and can cut weeks off a research trip. “There are many applications for our technology – undersea archaeologists and surveyors often need to send pictures to the surface, which is done using acoustic techniques. These kinds of sub-sea monitoring devices are also used for everything from environmental observation and checking the integrity of oil and gas pipelines, to oil field exploration and coast guard activities. As a result, the seas are a very noisy place. Our technology will not only help researchers to get their data more quickly and for a lower cost, but will also reduce their CO2 footprint and the environmental impact of their research on the great variety of underwater life”. Email Dr H K Yeo Pointers * The technology allows acoustic data signals to be simultaneously sent by different sources under the sea, so reducing data transmission time by about two thirds * Signal strength is only about 1/500 to 1/800 of that required by conventional technology * Equipment has been developed that will allow the technology to be deployed to depths of 10,000m