The control of the presence of micro-bubbles and the characterization of their size distribution is still an open question since it is crucial for various applications. Regarding medical concerns, one can mention the development and characterization of Ultrasound Contrast Agent, the prevention of pulmonary, cardiac and cerebral embolisms as well as for decompression sickness. Present in Blood and in tissues, these bubbles may result either from super saturation during decompression or may originate from extra or intracorporal medical devices. In the industrial context, specific concern is raised by the presence of micro- bubbles coolant, which biases the ultrasonic control process and may entail heavy consequences for the core security.