Deep ocean experience with acoustic current meters

As possible replacements for our venerable VACMs and VMCMs, we have been testing a number of modern current meters which are based on sound propagation principles, either travel time differences between transducers or Doppler frequency shift due to scattering from suspended particles. Comparisons with our traditional instruments, which have mechanical sensors, have produced more questions than answers and after four different experiments in the deep ocean near Bermuda, we are not yet able to provide definitive conclusions.