  The interaction between microbubbles through pressure pulses has been studied
to show that it can be a source of cavitation noise. A recent report
demonstrated that the acoustic noise generated by a shrimp originates from the
collapse of a cavitation bubble produced when the shrimp closes its snapper
claw. The recorded acoustic signal contains a broadband noise that consists of
positive and negative pulses, but a theoretical model for single bubbles fails
to reproduce the negative ones. Using a nonlinear multibubble model we have
shown here that the negative pulses can be explained by considering the
interaction of microbubbles formed after the cavitation bubble has collapsed
and fragmented: Positive pulses produced at the collapse of the microbubbles
hit and impulsively compress neighboring microbubbles to generate reflected
pulses whose amplitudes are negative. Discussing the details of the noise
generation process, we have found that no negative pulses are generated if the
internal pressure of the reflecting bubble is very high when hit by a positive
pulse.
