The use of higher order statistics to classify the non-linear behaviour of bubbles

The appearance of bubbles in fluids is an important phenomenon, and the ability to determine size and count bubbles has practical applications in a wide area of studies. Traditionally bubbles have been detected using either optical methods or by the interaction of an acoustic field with the bubble. Acoustic techniques have the ability to discriminate between solid and gas particles and can be directly related to the size of the bubbles. There exists a wide range of acoustic techniques, some of which exploit the non-linear acoustic response of the bubble. Each of these techniques has its limitations. This paper describes methods by which scattering data can be analysed using higher order statistics to characterise the non-linear response. Estimates of the second order transfer function are presented