Higher harmonics of vibrating gas-filled microspheres. Part two: measurements

Acoustic measurements on diluted Albunex at two driving frequencies (1 and 2 MHz) are reported which show that the level of the second-harmonic response is about 20 dB below the first harmonic at an acoustic pressure amplitude of 50 kPa. It is demonstrated that, under controlled conditions, it is possible to discriminate between Albunex and other scattering/reflecting objects using the non-linear behaviour of the microspheres.