Acoustic logging technique uses a transducer to transmit an acoustic wave through the liquid in a borehole and the surrounding rocks. Several types of acoustic tools are in use.
The tools differ in the frequencies used, the way the tool records the signal, and the purpose of the log.
However all require liquid in the borehole to couple the signal to the surrounding rocks.
Three types are available: acoustic-velocity (sonic log), acoustic televiewer / Imaging, and acoustic wave form (full wave sonic – FWS).
Acoustic logs are very powerful because they can provide data on porosity, lithology, hole / casing integrity, the location and character of fractures, earth stress fields, casing inspections, caliper measurement, and seismic velocities (utilized to tie-in with seismic surveys).