Geoacoustic inversion of transmission loss data


  • Abrahamsson Leif
  • Andersson Brodd Leif
  • Ban Stefan
  • Dalberg Eva
  • Söderberg Per

Publish date: 2006-01-01

Report number: FOI-R--2020--SE

Pages: 24

Written in: English


This report presents results of geoacoustic inversions based on broadband transmission loss data in the frequency range 0.1-4 kHz. The acoustic measurements were made in June 2005 in a coastal water area off Nynäshamn. High frequency signals were used to estimate the thickness of a low-speed surficial sediment layer. The inversion revealed that the thickness varied of the order 0-10 m both by range and azimuth. The bottom parameters of an underlying sediment were determined by inversion of low frequency data. Also this sediment showed varying characteristics along different measurement tracks. In the inversion, bottom parameters are searched that give a best fit of measured and simulated sound fields (the matched-field technique). Two sound propagation models, one based on ray tracing and the other one on the parabolic wave equation, were used. Comparisons between this experiment and a previous inversion study of reflection loss data from the same site are presented with respect to inversion results and their importance to operational rapid environment assessment (REA). Guidelines for future work on inversion techniques based on mobile data acquisition systems are proposed.