The ABS Acoustic, Bubble Spectrometer ^®© is a commercially available acoustics based device that measures bubble size distributions and void fraction of bubbles in liquids. The initial efforts to develop the technology were funded by Small Business Innovation Research (SBIR) awards from the National Science Foundation. Continued developments were funded by institutions and companies in both public and private sectors, including Department of Energy, Oak Ridge National Laboratories, and many other private companies. The ABS Acoustic Bubble Spectrometer^®© is under constant development, driven by new commercial applications and by the request of customers using the instrument to address their specific applications.

Principle :
The device extracts the bubble population from acoustical measurements made at several frequencies. It consists of a set of two transducers/hydrophones connected to a computer. A data acquisition board controls the hydrophones' signal generation and acquisition. The PC is also used for analysis of the data and provides, using Dynaflows software, the sound speed and attenuation as a function of frequency.

The bubble population can be obtained from these measurements by a solution of two Fredholm Integral Equations of the first kind. These equations are ill-posed and are a challenge to solve - especially when the data has noise. In our research, we developed novel algorithms that are able to accurately solve these equations using a constrained optimization technique.

The instrument can provide the data in near real time, thus making it suitable for process applications. The bubble distributions from the ABS Acoustic Bubble Spectrometer^®© have been validated by comparison with micro-photography.

Advantages:
Compared to optics based devices, ABS Acoustic Bubble Spectrometer ^®© is inexpensive and easy to use. In addition, the acoustic technique is very sensitive to bubbles and is not fooled by the presence of particulate matter which are not readily distinguishable from optics.