Audio logging. A logging process for measuring the amplitude of background [[noise]] in the wellbore environment, for specific frequencies in the audible range, at selected stations in the hole. Moving fluids, liquids or gases, generate characteristic sounds having frequency spectra and amplitudes which can be interpreted. The [[signal]] amplitude is proportional to the amount of work performed by the fluids in motion and to the location of the [[tool]] with respect to the level from which noise emanates. Can be useful in ascertaining fluid-movements behind tubing or casing.