Thursday, March 15, 2012 Sonardyne International, UK, has
retrieved its first Pressure Inverted Echo Sounder (PIES) off
the coast of Hawaii, USA. This new long-life sensor logging node
is designed to accurately measure the average sound velocity
through a column of water from the seabed to the sea surface.
The information gathered will help oceanographers to better
understand the dynamics of the ocean and atmosphere-ocean
coupling. On 24th September 2011, the Sonardyne PIES was free-
fall deployed into a 960-metre-deep water channel close to the
big island of Hawaii, and commanded to log average sound
velocity readings every seven minutes. Now, engineers have
returned to the site and recovered the unit by acoustically
commanding it to float to the surface under its own buoyancy.
Pressure inverted echo sounding is a technique that works by
transmitting an acoustic pulse upwards from a PIES instrument on
the seabed. The pulse is reflected off the water-air boundary at
the sea surface and returns back down to the