UACE2017 Proceedings: Time Domain Active Sonar Performance Prediction in Shallow Waters

• Session:
  Sonar performance modeling and verification - Applications to active and passive sonar
• Paper:
  Time Domain Active Sonar Performance Prediction in Shallow Waters
• Author(s):
  Jörgen Pihl, Lennart Bossér
• Abstract:
  Traditionally sonar performance prediction is done by calculating the transmission loss in the frequency domain by means of a wave propagation model. For active sonar the reverberation level is also calculated. Then the sonar equation is used to obtain detection distances. This works well for passive sonar, with typical integration times of 10 s or more. However, for modern broad band active sonar which may have a bandwidth of 3 kHz or more, corresponding to a time resolution of 0.3 ms, the frequency domain approach may not work so well, especially not in shallow waters. The reason is that the transmitted pulse usually is split by multi-pathing, so that the acoustic energy is spread over time. Also the target itself, depending upon aspect angle, can cause a time spread. The result is that detection distances are overestimated, and a correction term for processing loss has to be added to the sonar equation. The experience from the Royal Swedish Navy is that this term can be as high as –12 dB. \nThis discrepancy between theory and experiment is of course unsatisfactory. At FOI we have therefore developed a new model, ROSES (Robust Operational Submarine Echo Simulator), which is a ray trace model coupled to a target strength model. The output (time series) from ROSES can be processed in a similar way as in sonar, resulting in a more realistic performance prediction. \nExamples will be given both from experiment and modelling, demonstrating broad band active sonar performance.\n
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Contact details

• Contact person:
  Dr Jörgen Pihl
• e-mail:
  
• Affiliation:
  Swedish Defence Research Agency (FOI)
• Country:
  Sweden