Measurement of turbulent sound speed fluctuations with an acoustic travel-time meter

An acoustic current meter measuring absolute and differential travel-time of water was deployed in the Hudson Estuary. One goal of the experiment was to make direct estimates of buoyancy fluxes. Results indicate that the absolute travel-time measurements were reliable in a mean sense but that the fluctuations were dominated by an electronic oscillation and a high noise floor. The absolute travel-time circuitry has been modified to remove the oscillation and reduce the noise floor. The oscillation has been almost completely removed and the noise floor has been reduced by more than an order of magnitude. The authors expect that buoyancy fluxes will be resolved in future deployments if a record of sufficient length is recorded