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"It's a sweep of energy or sound, that takes off - that's why we call it a multi-beam. And what happens, it starts on one side of the vessel, and sweeps all the way around to the other side of the vessel - and stops - and then we listen for that sound to come back. And when that sound comes back it we can hear a 'click' - which is the sound coming back to the vessel. But the 'sweep', because it starts off and goes 'swoouup' - like a bird - 'swoouup', and that is the sweeping of the sound across the hull of the vessel - so that we can produce a sound map that is along a swath - and normally the swath width is around six to eight kilometers.

Here you're not hearing the 'click'. I don't know if you can hear it now, but you can hear it go off and come back." (sound: clicking)