LEBU is a device for towed acoustic arrays. The purpose of the device is to reduce f noise around the towed array.

The LEBU includes two identical circumferential airfoil

Airfoil

An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....

s and two flat flanges. The flanges secure the device to a coupling on the towed acoustic array.
This is helpful when using sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

 or Echo sounding

Echo sounding

Echo sounding is the technique of using sound pulses directed from the surface or from a submarine vertically down to measure the distance to the bottom by means of sound waves. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes...

.

The device is .