The attenuation constant in air of acoustic amplitudes has been measured for pressures from 2.3 to 0.18 atmos in a cylindrical tube of 5.16‐cm diameter and in cylindrical capillary tubes of 0.10‐cm and 0.15‐cm diameter. In the first series of measurements the amplitude of stationary waves in the wide tube is measured as a function of the distance to the end, and the attenuation constant calculated. In the second series of measurements the measuring tube is closed by a sample of capillary tubes; the absorption coefficient and the phase difference at the input of the samples are measured and from that the attenuation in the capillary tubes is calculated. In both cases it is found that the theoretical values of Kirchhoff‐Helmholtz are about 13% lower than the mean experimental ones.

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