Marine burglar alarm squawks at the sound of bubbles

日期:2019-03-02 05:01:11 作者:席思橘 阅读:

By Colin Barras (Image: Tuncay Akal) (Image: Donald A Frey/Tufan Turanli) An estimated 1 million ancient shipwrecks litter the seafloor around the globe, proving a tempting target for looters and a nightmare for archaeologists and governments to protect. But that could be set to change with the advent of a submarine alarm that can identify the telltale sounds of approaching treasure hunters in the hubbub of the oceans. Recent technological advances have been a boon for underwater research – improvements in GPS navigation, sonar and diving gear mean ancient shipwrecks are more accessible than ever. But archaeologists worry that the same advances will also benefit looters seeking to make a quick profit. Tuncay Akal of the TÜBİTAK-Marmara Research Center in Kocaeli, Turkey, is a member of an international research team designing an early warning system that can identify plunderers by their acoustic signature and alert officials of their presence. The sea is a noisy place, with fish, storms and shipping all adding to the cacophony. But Akal says it is possible to pick out looter’s noise from the mix by using vector sensors to record the direction of sound waves and identify specific sequences of sounds. Thieves are most likely to approach remote wrecks in a speedboat. And, as a boat’s propeller generates a characteristic acoustic signature, this can be used to spot intruders. To avoid false alarms from boats passing nearby but not stopping, the system listens for engines being switched off in close proximity to the wreck. “Once the propeller stops, the system begins monitoring at a higher frequency,” says Akal. “That’s to identify guys in the water.” Since looters are likely to be equipped with scuba gear to enable them to dive down to the wreck, the system is trained to listen out for acoustic signatures from the bubbles released during breathing. That specific acoustic sequence – a speedboat propeller stopping above the wreck, followed by scuba bubble noise – activates the alarm. A signal is sent via a wire to a floating buoy, which passes it on using radio to a surveillance centre on shore. Tampering with the device would also trigger an alert call. Akal acknowledges there are still problems to address – thieves could row a boat to the wreck, “but it’s difficult to row out all the equipment they need,” he says. It’s also possible that divers would use a closed-circuit system, in which air isn’t released into the water during breathing, which would make spotting them from an acoustic signal much harder. “But I’m confident we’ll be able to build a functioning prototype,” Akal says. That prototype will be tested on a vulnerable late Roman wreck, submerged in just 50 metres of water near Bodrum, Turkey. Earlier this month,