A resonance‐tube method has been developed for the measurement of sound absorption and velocity in gases at frequency to pressure ratios from 36 to 3800 cps atm. Measurements in oxygen at 30°C show velocity dispersion and excess absorption due to relaxation of the vibrational mode of the oxygen molecule with a relaxation time of 3.2±0.3 × 10−3sec. The results are in agreement with those obtained by Knotzel and Knotzel.