Figure 10: Sound measured at the hydrophone rig closest to the marine vibrator. The upper panel shows some examples of 23 second long recordings with 1 second break of the continuously repeated 10 seconds long marine vibrator sweep signals. The Frequency content of a 10 s long section (marked with yellow in upper panel) is shown in the lower panel. There are peaks at 11 and 29 Hz (also at 1.7 Hz outside the hydrophone sensitivity). All the energy seems to be below 150 Hz.