Hongkong's South China Morning Post reported on January 22, 2018 that the Chinese Academy of Sciences had this month disclosed that it has planted two powerful cutting-edge acoustic sensors – some of which have a listening range of more than 1,000km – for scientific research such as studying earthquakes, typhoons and whales near Guam, America’s biggest military base in the Western Pacific. The high-end surveillance devices have been in operation since 2016. One of the acoustic sensors is located in the Challenger Deep of the Mariana Trench – the deepest place on Earth at 10,916 metres beneath sea level – and another is near Yap, an island in the Federated States of Micronesia. Security experts say the sensors can also track the movement of submarines in the South China Sea and intercept underwater signals between the submarines and their command base. According to the Chinese Academy of Sciences, which oversees the development and deployment of the acoustic sensors, the devices are attached to a long cable along the sea floor and the cable is connected to a small buoy carrying satellite communication devices and supplying more than a year’s worth of battery power to the devices, which are small and consume very little power. The Chinese Academy of Sciences also said the Chinese deep-sea surveillance networks have survived the crushing pressure at the world’s greatest depths and picked up noises from sources over 1,000km away. They are regularly maintained by Chinese research vessels.

Zhu, who leads programmes on deep-sea surveillance and communication at the Chinese Academy of Sciences Institute of Acoustics, said “The deeper under the surface, the quieter the world becomes, and it allows us to concentrate on the signal we most want to hear.”He added there was an export embargo to China on sound detectors with operational depths beyond 1,000 metres and that such devices were difficult to produce as they required special materials and sophisticated technology to ensure they could continue collecting accurate information for long periods under extreme, high-pressure environments. Saying the sensors are small and consume very little power, Zhu did not reveal further details of how the sensors are made, but said “it is a breakthrough for China”.