[Discretion and stealth] Close-up on Merou, Naval Group’s cutting-edge acoustic coating test instrument

04 December 2023 Innovation Submarines News

Acoustic discretion and stealth are fundamental performances in modern submarines and rely on absorbent material used to coat the hull. This material must first complete full qualification cycles before it can be considered operational and used on submarines. Here are a few explanations as to why Naval Group decided to develop a measuring instrument for the acoustic characterisation of materials.

Development studies on future submarine programs are ongoing, especially those on hull coating materials, the reason why specialists in the field of acoustic coating were brought together to form a cross-functional unit. One of their main aims is to qualify hull coating material to optimise the acoustic performances of our ships. In collaboration with this unit, the Underwater Detection Department (UWD) developed an instrument to test material at sea and named it *Merou which in French stands for acoustic coating test instrument. A considerable amount of work has gone into designing and developing Merou, which happens to be the only such test instrument known to date, capable of measuring acoustic performances full-scale, i.e. in an acoustic free field, underwater and at frequencies of use. The French Defence Procurement Agency (DGA), satisfied with its performances at sea - field of use, accuracy, reliability, repeatability etc. - accepted the instrument in 2021. 


A successful test run in the Mediterranean in August

Merou is capable of measuring performances of different kinds of material such as micro-inclusion (polymer matrix containing inclusions much smaller than the wavelength) and macro-inclusion type material. “The acoustic performance of four materials of two different kinds was successfully measured when this instrument was launched into the Mediterranean Sea from a support ship last August. These measurements help Naval Group teams developing coating material to better understand their acoustic characteristics and to make improvements keeping their operational application in mind”, explains François Dayet, Systems Manager and Technical Manager for these tests at sea. This success makes Merou an indispensable measuring instrument as far as qualifying coating material is concerned. A new set of tests at sea for new material is already in the offing. The next steps after these tests include the acoustic validation of prototypes followed by the validation of materials for the finalised series.

*Merou: moyen d’essai de revêtement acoustique