I have been working on processing the acoustic data from the HTI hull mounted echosounding system. Essentially, the way echosounders works is to send a pulse of sound (aka a 'ping') down into the water and then listen for the echoes that scatter off of the animals and other objects (e.g., the bottom) in its path. Our system operates at four frequencies that we ping on in sequence, and we use the 'backscattered' echo data to tell us something about the abundances and kinds of animals that are here.
The data are most easily displayed in something called an Echogram. Echograms are colorful figures that display the acoustic backscatter data in a way that is easy to understand. They are a snapshot of the water underneath the ship over a specified time, typically a day. By looking at all four frequencies, we can get an idea of what the various patches seen might be, since different kinds of animals scatter sound differently as we change the frequency. It's been very interesting to be able to see the changes in backscatter as we travel through different water masses!
Click on the picture below to enlarge and learn more about how to read an echogram!