Figure 10. High-passed filtered Recordings by the outer sound trap hydrophone. a) show the sailing track for the measured sound level in b). The vessel is approaching the bay, sailing direction indicated by the arrow, ending up with the marked red circle. In b) the sound signal can be seen as increasing as the sparker is starting transmitting at time = 300, and reaching maximum as the hydrophone position is passed and then decreasing as the vessel moves away. In c) a 10 sec time period is zoomed in to see the individual signals. As can be seen here, one signal is transmitted every second. d) Same duration as for b) for the inner hydrophone, showing that the sparker signal here is not detectable above the background noise level.
