Reconstruction of the bistatic response of an elastic object with edges using its estimated acoustic impedance matrix from diffuse field acoustic holography

This study aims to compute the bistatic response of an elastic object submerged in water based on preliminary measurements of its mechanical impedance in air. This approach allows to predict the field scattered by the object in any environment without prior knowledge of its internal structure, relying on a single measurement. The object's mechanical impedance, which is its response in a vacuum, is estimated in a diffuse noise field. The pressure is measured on two conformal holographic surfaces near the object. Incoming and outgoing fields are separated using either the method of equivalent sources (for objects without geometric discontinuity) or a new alternative method for objects with edges. For more accurate velocity reconstruction in air, the acoustic response of a rigid object with the same shape is computed numerically and then subtracted. Pressure and velocity fields are retropropagated to extract the mechanical impedance matrix which is then used to calculate the bistatic response in water. The approach is tested numerically with two plastic cylindrical shells: one without geometric discontinuity and one with edges. Results demonstrate the possibility of reconstructing bistatic responses in water for both object types, with higher accuracy for objects without discontinuities.