Sight is arguably our most important sense, accounting for the vast majority of information we take in from the world around us, but as nature’s echo-location has proven, sound can reveal much more than meets the eye. On this month’s show, we learn about the high-tech companies using sound in places too dark, dense or dangerous for us to see. This information has a whole range of safety applications in the energy and transport industries, as well as helping oil companies in the search for the black stuff.