EXPERIMENTAL APPROACH TO A COMPLEX ACOUSTIC SYSTEM

A liquid is subjected to sound of high intensity to generate a cloud of cavities or bubbles. The correlation between the sound output from the bubble cloud, which follows a subharmonic route to chaos with a low-dimensional strange attractor, and its spatial dynamics is investigated. Several approaches are used. In a light transmission experiment the light modulation resulting from the spatial dynamics gives an integrated measure similar to the acoustic output from a hydrophone. High speed photographic cinematography and, in particular, methods of high speed holographic cinematography are used and developed to capture the spatial dynamics of the three-dimensional bubble pattern, a filamentary structure resembling Lichtenberg figures. The series of three-dimensional images obtained via holography is digitized and analyzed via a transputer-based digital image processing system. First results show strong correlations among the behavior of individual bubbles and indicate a highly cooperative system. The method of high speed holographic cinematography developed together with a digital holographic image processing system will also be of use for the investigation of other complex space-time systems, for example, the Rayleigh-Benard and Taylor-Couette systems, and is scheduled for fully three-dimensional turbulence studies.