i'm joined again by awudio expet paul gensburg. some might sound blurry or insignificant. the audio experts how they tell the difference. >> okay. what i've done is prepared a simulation for you. first i have a pure tone as if it was coming from a pinger. and we can play that. nice and clean. right? but, once we submerge it down three miles and we start to listen from the surface, we're going to hear it embedded in ocean noise. >> you can barely hear it. >> that's right. and if you don't know what you're listening for or if you're not in range you won't hear it. >> can we put that one up again? let's put that one up again, paul. this is what it sounds like and you're wondering about the sound and why they -- >> why they have trouble hearing it. >> is that ocean rain or is that just how the ocean sounds? >> no, this is a simulation using a largeme amount of white noise. in the ocean we have white noise but also, as fabien said, a lot of other manmade noises and natural sounds. so what i did was, i employed some forensic audio techniques, some of which were the same that i u