Introduction:
If one wishes to measure
a bubble population, one of the most useful methods is
active acoustic bubble spectroscopy.
In this, a sound field is projected into the bubbly liquid.
The interaction of the sound field with the bubbles produces an
acoustic signal which may be inverted to estimate the numbers of bubbles
present and their radii.
(This
can be contrasted to
passive acoustic
bubble spectroscopy (a tutorial on which
can be accessed by clicking
here)
where the bubble population is diagnosed simply by listening to the
emissions made by the bubbles: no incident sound field is projected at
the bubbles).
In summary therefore, to
achieve
active acoustic bubble spectroscopy
one must undertake 3 procedures:
[1]
Insonify bubble population
[2]
Monitor effect on sound speed, attenuation, scatter
[3] Invert
acoustic data using suitable model
Because of this, the
various methods of
active
acoustic bubble spectroscopy
have features in common, which will be colour coded in the following
schematic:
For the
homepage of the Ultrasonics and Underwater Acoustics (UAUA) Centre, click 
© T G
Leighton 2003