PASSIVE ACOUSTIC MAPPING USING COMPRESSIVE SENSING

A passive compression wave imaging system for locating cavitation bubbles, the system comprising a plurality of sensor elements (202b) arranged in an array and each arranged to produce an output signal, and processing means (204a, 204b) arranged to: define a sample period, and a sample space over which the signal can be sampled at each of a plurality of sample points in the sample space; define a grid of candidate bubble positions; define a random projection identifying a respective different group of the sample points for each of the output signals; sample each of the output signals at the group of sample points defined by the random projection to generate sample data; define a dictionary which defines the sample values that would be obtained for the signal of each of the respective group of sensor elements at each of the sample points for the sample period for a bubble at each of the candidate bubble positions; define a vector the elements of which identify the candidate bubble positions; and perform a minimisation operation to derive the vector element values, and hence the bubble positions, from the sample data, the basis and the random projection.