The waves mainly come from a loudspeaker beyond the top, and are reflected from surroundings. It is possible to see the reflected waves as fainter ones among the strong ones, and they are going in other directions.
I made the objective to be one meter across, and it is equivalent to about 10 000 microphones, taking 50 000 pictures each second.
This wave field is used to make pictures with my sound camera.
By Kim Øyhus (C) 2013-11-11