Powerful acoustic (sound) waves are vertically generated towards the seabed by a SBP transducer, either mounted on a pole and lowered from a vessel, on an unmanned surface vehicle or by remote-operated underwater sled.

Some of this wave energy reflects off the seabed, returning to the transceiver, while some penetrates the seabed and reflects off materials below the surface, also reflecting to the transceiver.

The longer the measured time taken for the different reflected waves to return to the transceiver, and knowing the speed of the acoustic wave in the water and seabed, the greater the calculated depth of each reflecting surface.

As the vessel or remotely controlled transducer head moves across a site, a continuous vertical slice of detected returns – or ‘acoustic curtain’ – is produced, with horizontal distance along the ‘x’ axis and depth below the transducer on the ‘y’ axis.

As well as the different times taken for these acoustic waves to return to the transceiver, other acoustic wave properties can also be deduced – and these can provide insight into the density differences associated with sediment layers or buried materials.