The IEMN Acoustic Test Tank enables a variety of experimental studies related to the marine field to be carried out as part of research work, student projects, and industrial services.
Its volume of approximately 300 m3 (length 8 m, width 6 m, depth 7 m) and its location in an open academic environment make it unique in France. It was originally built in a hangar in 1985 for underwater acoustics applications in the 2–200 kHz frequency range, thanks to funding from the Region and the DRET. It was integrated into the ISEN building during its extension in 1998 and then rebuilt in 2022 in a new JUNIA building.

Acoustic measurements in water are essential for studying devices, structures, and materials intended for underwater use. They provide a good assessment of performance before moving on to measurements in “real” conditions (in lakes or at sea), which are much more logistically and financially burdensome. However, they require precise identification of the influence of the finite dimensions of the tank on the measurement in order to enable reliable extrapolation. As such, the acoustic test tank is an important metrology tool for research and industry.

The research conducted in the Acoustic Test Tank mainly concerns three areas of application:

Defence : sonar, acoustic discretion and stealth,

Oceanography : seabed imaging,

and the Environnement : control of anthropogenic noise in the ocean in connection with UN SDG 14.

They are often carried out within the framework of industrial partnerships (Naval Group, Thales, Exail, Soacsy, Greenov, etc.) and supported by the ANR ASTRID program. The main challenge at present is that of low frequencies (frequencies below 1 kHz, wavelengths from a few meters to a few tens of meters), which require new concepts to produce effective sub-wavelength-thick screens or coatings and compact broadband sources. The issues addressed concern both the experimental study of physical problems (acoustic panels based on metamaterials, vibration control of plates by nonlinear energy wells, low-frequency and broadband transducers for seabed imaging) and the development of new characterization methods (3-point and 5-point methods for determining the acoustic fields transmitted and reflected by metapanels).

Several measurement benches in the acoustic test tank are used regularly as part of services provided to companies:

Pressure levels measurements via hydrophones/reference transmitters to evaluate acoustic source (TVR transmitting voltage response, SPL sound pressure level, directivity) and hydrophones specifications (FFVS free-field voltage sensitivity, directivity), measurement of the reflection and transmission coefficients of acoustic panels (insertion methods, 3-point and 5-point methods).

These measurement methods are described in detail in [Pouille 2024].