Standing acoustic field testing
| Project acronym: | HyIII-NTNU-5 |
| Name of Group Leader: | Prof. Sergio Jesus, University of Algarve, FCT, Campus de Gambelas, Faro, Portugal, sjesus@ualg.pt Prof. Antonio Silva, University of Algarve, FCT, Campus de Gambelas, Faro, Portugal. asilva@ualg.pt |
| User-Project Title: | Standing acoustic field testing |
| Facility: | Research Vessel |
| Proceedings TA Project: | An environmental equalizer for underwater acoustic communications tested at hydralab iii |
| Data Management Report: | Data Management Reports Page You will need to login to view this page |
Summary:
The UAB project aims at studying, developing and testing acoustic methods for protecting critical infrastructures. The UAB07 experiment served at: i) testing high frequency signals off the busy port of Trondheim, Norway, and ii) proving the acoustic barrier concept in an acoustically quiet and environmentally stable location in the Hopavaagen bay, 200 km from Trondheim, Norway. This report concentrates on the experiment carried out at the Hopavaagen bay, from September 9 to 13. The location turned out to be ideal for deploying the source and receiving array and its operation from land. The time spent in equipment installation and extensive debugging of hardware and software resulted in practice in only half day of actual acoustic barrier data. The results obtained confirmed an extremely stable environment with reproducible conditions in short (minutes) and long (hours) time frames. Parallel results obtained with simulations and not shown in this report showed that the limited environmental data gathered during the sea trial was sufficient to run computer models for determining signal propagation conditions that can explain the transmission patterns found during the experiment. However, due to two major drawbacks it appears extremely difficult to achieve target detections with the observed data sets. These drawbacks are:
- the limited number of receiving channels (4) due to the replication of every forth channel in the following three.
- the loss of synchronization between the two source received signals before reciprocal retransmissions.
As recommendations for future experiments and apart from the obvious correction of the above mentioned drawbacks, future experiments involving acoustic barriers should account for: i) saving reciprocal signals as transmitted from source array, ii) high precision GPS for surface buoy location through time, iii) real time correlation of received signals with time-reversed replica of the emitted signal before channel summation and iv) if possible, increase the number of sources in the active array.
| Publication References |
| Experimental assessment of time-reversed OFDM underwater communications, proposed to Acoustics ’08, Paris, June 2008 J.P. Gomes, A.Silva and S.M. Jesus. |
| Underwater Acoustic Barrier 2007 (UAB’07) Experimental Data Report, Rep. 02/08, SiPLAB Report, University of Algarve, February 2008, S.M. Jesus, A.Silva, C. Martins and F. Zabel. |
| OFDM Demodulation in Underwater Time-Reversed Shortened Channels. Oceans ’08, Quebec, Canada, 15-18 September, Gomes J.P., A. Silva and S.M. Jesus (2008). |