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• Supersonic shear imaging elastography can measure cortical stiffness in renal transplants • The level of cortical stiffness is correlated with the global degree of tissue lesions • The global histological deterioration of transplanted kidneys can be quantified using elastography.

This paper investigates the efficiency of a field separation method for the identification of sound sources in small and non-anechoic spaces. When performing measurements in such environments, the acquired data contain information from the direct field radiated by the source of interest and reflections from walls. To get rid of the unwanted contributions and assess the field radiated by the source of interest, a field separation method is used. Acoustic data (pressure or velocity) are then measured on a hemispheric array whose base is laying on the surface of interest. Then, by using spherical harmonic expansions, contributions from outgoing and incoming waves can be separated if the impedance of the tested surface is high enough. Depending on the probe type, different implementations of the separation method are numerically compared. In addition, the influence of the walls' reflection coefficient is studied. Finally, measurements are performed using an array made-up of 36 p-p probes. Results obtained in a car trunk mock-up with controlled sources are first presented before reporting results measured in a real car running on a roller bench.

Numerous practical applications -such as non destructive evaluation of industrial structures, acoustic characterization of musical instruments, and acoustic mapping of sound sources in aknown propagation medium -involve source detection and characterization. In the past, this problem has been investigated using different beamforming and backpropagation methods. In this work, anew technique, based on the time reversal sink concept, is used to detect active sound sources with alimited number of measurement points. The theory and application of superresolution focusing of sound and vibration using atime-reversal sink (TRS)havebeen studied, both in ultrasonic regime and in audible range. Ah igh-resolution imaging technique based on an umerical time reversal sink has recently been developed by the authors for vibrational imaging of active sources in adispersive medium. In this paper,the numerical time reversal sink imaging technique is adapted to the case of high-resolution acoustic imaging of active sound sources in athree-dimensional free field. This technique allows high-resolution imaging and provides anew method of characterization and detection of sound sources. All results showthe high resolution imaging capabilities of this newt echnique when compared with classical time-reversal (TR) backpropagation. More than simply detecting the position of the acoustic source, this technique allows to detect the size of the active sources. This technique provides an alternative to other imaging and source detection techniques, such as three-dimensional acoustic holographyand beamforming.

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