Safety and improved performance
TNO has been conducting research on underwater acoustics for some time, for clients such as the Royal Netherlands Navy and projects such as the construction of offshore wind parks in order to lessen the adverse consequences for marine mammals.
Recent acoustic projects have focused on the safety of swimmers and divers and improving athletic performance in the water. Together with interested parties such as the Diving and Underwater Explosives Group of the Dutch Ministry of Defence, the InnoSportLab de Tongelreep swimming performance laboratory in Eindhoven and specialist companies, TNO is developing new applications for underwater communication.
A new generation of wearables have been successfully tested in the Pieter van den Hoogenband research pool in Eindhoven. These small devices attached to a swimmer’s skin send metrics such as heart rate, stroke rate, swimming stroke and swimming speed to a receiver at the bottom of the pool.
These tests were conducted as part of the EU-funded project SILENSE, with partners such as the Holst Centre, foreign research centres and companies. The devices were attached to the chest, wrists and ankles.
Underwater acoustic data transmission
Basis for new standards
As yet there are no standards for this form of short-range data communication and there are various technical hurdles that still need to be resolved. These include the fact that the unpredictable movements of the water's surface disturb the acoustic signals as they travel between the sender and the receiver.
We have found ways to largely eliminate the different forms of disturbance. One is to send short acoustic pulses, in which the data is stored redundantly in terms of both time and frequency, to the side of the pool.
The European research and successful tests in the swimming pool will play a key role in helping to improve the performance of swimmers, but for TNO this is the start of many more applications for the Ministry of Defence, sport and consumers.
Underwater acoustic data transmission is an enabling technology: an invention or application that proves suitable for other purposes. In the first instance the challenge is to develop a thin and easily wearable device for the consumer market that raises an alarm when someone has been underwater for too long.
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