  This paper describes the calibration procedure for the drift tubes of the CMS
barrel muon system and reports the main results obtained with data collected
during a high statistics cosmic ray data-taking period. The main goal of the
calibration is to determine, for each drift cell, the minimum time delay for
signals relative to the trigger, accounting for the drift velocity within the
cell. The accuracy of the calibration procedure is influenced by the random
arrival time of the cosmic muons relative to the LHC clock cycle. A more
refined analysis of the drift velocity was performed during the offline
reconstruction phase, which takes into account this feature of cosmic ray
events.
