Stephane Beretti
DCN Ingenierie Sud, Dept. of Underwater Warfare, BP 30, 83800 Toulon Naval, France
Christian Audoly
DCN Ing. Sud., Toulon, France
Philippe Guillaussier
PONS, 13872 Aubagne Cedex, France
The microinhomogeneous materials made with air-filled cavities in
viscoelastic matrices, have many possible uses in underwater acoustics
including anechoic coatings, acoustic decoupling, or reflectors for arrays.
Theoretical models are necessary to predict the acoustic properties of these
materials by evaluating the properties of the equivalent homogeneous material,
as a function of frequency, pressure, and temperature. During recent works an
abnormal effect of the applied pressure on these materials was noted: The plot
of the longitudinal sound speed and of the bulk modulus, versus static
pressure, had the lowest value for 10 to 20 bars of applied pressure, instead
of a regular increasing plot predicted by the models [G. Gaunaurd et al.,