To determine the absorption in a reverberation chamber for PWL measurements. the reverberation‐time method (using the Sabine formula) is preferable to the calibrated‐source method. This preferred method, which is independent of the source or measuring‐equipment calibrations, involves a device attached to a graphic level recorder to indicate the reverberation time on an electronic counter. The 10 logafactors for three reverberation chambers determined with this device are compared to determinations which were obtained with: (1) a graphic level recorder and (2) a calibrated source.