Underwater sound data were collected using (i) autonomous recording units and (ii) cabled
hydrophones deployed from a vessel.
Longer-term data collection was made using acoustic recorders on seabed mounted frames.
Each frame consisted of a steel tripod with a cross-strut at the base to hold the frame rigid.
A hydrophone was mounted at the centre of the frame using nylon rope secured between
the top (apex) and bottom strut of the frame, in such a way that it would be suspended in
the water without direct contact with the frame or surrounding apparatus. Watertight
autonomous recorders were used with each frame to house the recording equipment and
electronics. The height of the frame apex was 1.2 m with the triangular base 1.5 m length
sides. Figure 2-1 a) shows four frames on Flamborough Light ready for deployment. Figure 2-
1 b) shows the autonomous DAQ system and hydrophone on an individual frame