When sonic pulses are introduced into the reservoir, the time taken to travel between fixed points can be measured.

The rate at which sound travels is related to the properties of the formation rock and the fluids it contains.

This information can be used for porosity estimation, fracture and lithology determination and correlation. 

This data can be used in drilling applications (such as pore pressure determination, rock strength calculations, borehole stability analysis) and in geophysical applications (for example time-to-depth seismic correlation and AVO analysis).