Sonardyne Acoustic Noise Shield

Description

The Type 7965 Acoustic Noise Shield has been degraded to reduce the effects of ROV generated noise on the performance of Long Baseline (LBL) acoustic positioning systems.

The LBL positioning method involves measuring ranges from an ROV mounted acoustic transceiver to a seabed array of transponders. ROVs and tether management systems often create substantial amounts of ultrasonic underwater noise from hydraulic power packs and thrusters. If the reply signals from the seabed transponders are swamped by this noise, acoustic navigation becomes problematic and may be impossible.

An ROV’s buoyancy pack can provide some ‘natural’ protection against this unwanted noise providing the acoustic transceiver is placed in the correct location and the buoyancy material itself is of the correct type. Shallow water (<600m) buoyancy provides the best noise shielding whilst deepwater syntactic foam (microspheres in a solid matrix) is acoustically transparent and thus provides little, if any, shielding.

The Sonardyne noise shield rejects noise signals from a 45 cone below the ROV’s transceiver in favour of ranges coming from MF seabed transponders out to the side.

The unique shape is optimised to preserve the hemispherical Beamshape of the transducers required for reliable LBL positioning whilst maintaining a clear acoustic path to the array.

Key Features
– Increases acoustic ranges by over 10 times in noisy conditions
– Depth rated to 3,000 metres
– Designed for Mini RovNav and RovNav transceivers
– Rejects noise from directly below the transceiver whilst maintaining hemispherical acoustic coverage
– Compact design for easy fitting to most types of ROV
– Approximately neutrally buoyant when fitted with Mini RovNav or RovNav Remote Transducer